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U. S. FLEET WEATHER CENTRALJOINT TYPHOON WARNING CENTER

COMNAVMARIANAS BOX 17

FPO SAN FRANCISCO 96630

ALBERT T. BUCKMASTERCaptain, United States Navy

COMMANDING

GARY D. ATKINSONLieutenant Colonel, United States Air Force

DIRECTOR, JOINT TYPHOON WARNING CENTER

STAFF

LCDR Leo H. Craiglow, Jr., USNLCDR Gordon W. Safley, USNLT Stephen G. Colgan, USNLT Orlin R. Scrivener, USNCAPT Charles R. Holliday, USAFCAPT Dennis M. Koyama, USAFlLT J. Francis Pratte, USAFMSGT Gerald E. Page, USAFSSGT Earl W. Schneider, Jr., USAFSSGT H. Ronald Wells, USAFAG3 Lawrence E. McMullen, USNSGT David A. Dow, USAFSGT Calvin L. Hyer, USAFSGT Edgar C. Riberdy, USAFAGAN Paul M. Cooper, USNAGAN Joseph Onder, USNAGAN Branko Pavlovic, USNMrs. Judy L. Hudson

CONTRIBUTOR

CAPT Charles P. Arnold, Jr., USAF, Det 1, lww

1973ANNUAL TYPHOON REPORT

The body of this annual report sum-marizes western North Pacific tropicalcyclones. Annex A summarizes tropicalcyclones in the central North Pacific from180° eastward to 140°W, and Annex B sum-marizes tropical cyclones in the Bay ofBengal. The eastern North Pacific tropi-cal cyclone summary has been discontinuedbeginning with the 1973 season; the U.S.National Weather Service will assume res-ponsibility for publication of this summaryin Marinerls Weather Log and Pilot Charts.

Fleet Weather Central/Joint TyphoonWarning Center (FLEWEACEN/JTWC), Guamhas the responsibility to:

1. Provide warnings to U.S.Government agencies for all tropicalcyclones north of the equator and west of180° longitude to the coast of Asia andthe Malay Peninsula;

2. Provide warnings for the areanorth of the equator from the MalayPeninsula west to 90”E;

3. Determine tropical cyclonerc?connaissance requirements and assignpriorities;

4. Conduct investigative andpost-analysis programs including pre-paration of the Annual Typhoon Report;and

Asian Tactical Forecast Center, Fuchu(formerly Air Force Asian Weather Central),coordinating with the Naval Weather Ser-vice Environmental Detachment, Yokosuka,is designated as the alternate JTWC incase of-the incapacitation of FLEWEACEN/JTWC Guam.

The JTWC is an integral part ofFLEWEACEN Guam and is manned by fourofficers and five enlisted men each fromthe Navy and Air Force. The senior AirForce officer is designated as Director,JTWC .

The western North Pacific TropicalCyclone Warning System consists of theJoint Typhoon Warning Center and the U.S.Air Force 54th Weather ReconnaissanceSquadron stationed at Andersen Air ForceBase, Guam.

The Central Pacific Hurricane Center,Honolulu, is responsible for the areafrom 180° eastward to 140°W and north ofthe equator. Warnings are issued incoordination with FLEWEACEN Pearl Harborand the Air Force Central Pacific ForecastCenter, Hickam Air Force Base, Hawaii.

CINCPACFLT, CINCUSARPAC, and CINCPACAFare responsible for further disseminationand, if necessary, local modification oftropical cyclone warnings to U.S. militaryagencies.

5. Conduct tropical cycloneanalysis and forecasting research.

iii

TABLE OF CONTENTSpage

CHAPTER I

CHAPTER II

CHAPTER III

CHAPTER IV

CHAPTER V

ANNEX A

ANNEX B

APPENDIX

OPERATIONAL PROCEDURES1. General ------------------------------- ------------------------2. Analyses and Data Sources ------------- ---------- --------------

Forecast Aids ---------------------- ----------------------- ----:: Forecasting Procedures -------------------------- --------------

Warnings --------------------------- -------------- ------------_

z; Prognostic Reasoning Message ----------------_____------------_

7. Tropical Weather Summary -------------------------------------_8. Tropical Cyclone Formation Alert ------- ----------------------_

RECONNAISSANCE AND COMMUNICATIONS1. General --------------------------- ------------------------ ----2. Reconnaissance Responsibility and Scheduling ------------------

3. Aircraft Reconnaissance Evaluation Criteria -------------------4. Aircraft Reconnaissance Summary ------------------------ -------5. Radar Reconnaissance Summa~y ------------------------ ----------6, Satellite Reconnaissance Summary ---------------------- --------7. Communications --------------------- --------------------- ------

RESEARCH SUNMARY1. General ------------------------- ----------------------- -------2. Investigation of Gust Factors in Tropical Cyclones ------ -----_3. Intensity Forecasting Using the TYFOON Analog Computer

Program ----------------------------------------- --------------

4. Evaluation of the Extrapolation Feature of the TYFOONAnalog Computer Program ------------------------ ---------- -----

5. A Comparison of the Sensitivity of Two Similar ObjectiveForecast Techniques ------------------- ----------- -------------

6. Interannual Variability of Rainfall and Tropical CycloneActivity in the Western North Pacific ------------- ------------

SUMMARY OF TROPICAL CYCLONES1. General Resume -------------------------- ----------------------2. Individual Typhoons -------- ------------------------- -------_--

TyphoonANITA---%& Typhoon LOUISE --%%Typhoon BILLIE -- 23 Typhoon MARGE --- 37Typhoon DOT ----- 25 Typhoon NORA ---- 39Typhoon ELLEN --- 29 Typhoon OPAL ---- 43Typhoon GEORGIA - 31 Typhoon PATSY --- 45Typhoon IRIS ---- 33 Typhoon RUTH ---- 47

3. Tropical Cyclone Center Fix Data --------------- ---------------

SUM?4ARYOF FORECAST VERIFICATION DATA1. Comparison of Objective Techniques ------ ----------- ---------- -

2. Summary of Tropical Cyclone Formation Alerts ------------- -----

3. Annual Forecast Verification --------------------- -------------4. Summary of Individual Tropical Storm Verification ---------- ---

Tropical Storm and Depression Data ------------------------- ---:: Typhoon Data -------------------------- --------------- ---------

SUMMARY OF TROPICAL CYCLONES IN THE CENTRAL NORTH PACIFIC1.2.3.

4.5.

BAY1.2.

3.4.

General Resume ---------------------- ----------------------- ---Individual Cases ---------------------- ---------------------- --Hurricane Tracks ------------------------- ---------------------

Hurricane DOREEN ~ Hurricane CATHERINE*Center Fix Data - Hurricanes ------------------------ ----------Position and Verification Data - Hurricanes -------------------

OF BENGAL TROPICAL CYCLONESSummary of Data -------------------------- ---------------------Tropical Cyclone Tracks ------------------------------- --------

J&ECyclone 33-73 --- Cyclone 37-73 --- wCyclone 35-73 --- 91 Cyclone 41-73 --- 93Center Fix Data ----------------------- ----------------------- -Position and Verification Data --------- ---------- -------------

ABBREVIATIONS, DEFINITIONS, AND DISTRIBUTION1. Abbreviations ----------------------------- --------------------2. Definitions ---------------------------- -----------------------3. Distribution ---------------------------- ----------------------

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CHAPTER I - OPERATIONAL PROCEDURES

1. GENERAL

Services provided by the Joint TyphoonWarning Center (JTWC) include forecasts oftropical cyclone formation, location, in-tensity, direction and speed of movement,and horizontal extent of critical windspeeds. This information was disseminatedin 1973 by: (1) Tropical Cyclone Forma-tion Alerts issued when formation of atropical cyclone was anticipated; (2) Tro-pical Cyclone Warnings issued four timesdaily whenever a significant tropicalcyclone was observed in the JTWC primaryarea; and (3) Tropical Cyclone Warningsissued twice daily whenever a significanttropicai cyclone was observed in the JTWCsecondary area.

FLEWEACEN Guam provides manual andcomputerized meteorological/oceanographicproducts for the JTWC. Communicationssupport is furnished by the Nimitz HillMessage Center of the Naval CommunicationsStation, Guam.

2. ANALYSES AND DATA SOURCES

a. FLEWEACEN GUAM ANALYSES:

(1) Surface mercator analysis,Northern and Southern Hemispheres, westernPacific and Indian Ocean areas; OOOOZ,06002, 12002, and 18002.

(2) Gradient streamline analysisof Asia and the western Pacific; “00002 and12002.

(3) Surface meso-analysis of theSouth China Sea region; OOOOZ and 12002.

(4) Composite surface analysis ofthe Indian Ocean area; twice daily.

(5) Sea surface temperaturecharts; daily.

b. JTWC ANALYSES:

(1) Gradient level (3,000 feet)streamline analysis (south of 20°N) andisobaric analysis (north of 20”N); 00002and 1200Z.

(2) 700-mb and 500-mb, contourand streamline analysis; 00002 and 1200Z.

(3) A composite upper troposphericstreamline analysis utilizing rawinsondedata from 250-mb to 150-mb and AIREPS ator above 29,000 feet; 00002 and 12002.

(4) Reconnaissance data. Obser-vations from weather reconnaissance air-craft are plotted on large-scale sectionalcharts.

(5) Time cross sections ofselected tropical stations.

(6) Additional and more frequentsectional analyses similar to those aboveduring periods of tropical cyclone acti-vity.

c. SATELLITE DATA:

Satellite data, especially DMSP(formerly DAPP) satellite imagery, played amajor role in the early detection of tropi-cal cyclones in 1973. This aspect, as wellas applications of satellite data to tropi-cal cyclone tracking, is discussed in Chap-ter 11.

d. RADAR :

Land radar reports, when available,were used for tracking tropical cyclonesduring the 1973 season. Once a storm movedwithin range of a land radar site, reportswere usually received hourly. Use of radarduring 1973 is treated in Chapter II.

e. COMPUTER PRODUCTS:

Use of the varian plotter by theFLEWEACEN Guam computeT center during 1973eliminated a significant portion of theJTWC hand plotting effort. Varian chartsare produced routinely at synoptic timesfor the surface, 850-mb, 700-mb, and 500-mblevels. Additionally, a chart of the uppertropospheric circulation is produced. Thischart uses 200-mb rawinsonde data andAIREPS above 33,000 feet and within sixhours of the 00002 and 1200Z synoptic times.Data not in the proper format for the com-puter are hand plotted on the charts.These include pibal gradient level winds,low cloud movement, and missing or latesynoptic reports necessary for a detailedanalysis.

In addition, the standard array ofsynoptic-scale computer analyses and prog-nostic charts from the Fleet NumericalWeather Central at Monterey, Californiaare available.

JTWC utilized extensively theFLEWEACEN Guam computer center for objec-tive typhoon forecasts and for statisticalpost analysis.

3. FORECAST AIDS

a. CLIMATOLOGY:

Various climatological publicationslisted in the Annual Typhoon Report, 1972(FWC/JTWC) were utilized in addition tothose received recently which include:

(1) Tropical Cyclone Climatologyfor the China Seas and Western Pacificfrom 1884 to 1970 (Royal Observatory, HongKong, 1972).

(2) North Pacific Tropical CycloneVector Mean Charts (Crutcher, H. L., 19731.

(3) North Indian Tropical CycloneVector Mean Charts (Crutcher, H. L. andNicodemus, M. L., 1973).

(4) A Climatology of Typhoon andTropical Storm Tracks Arranged by Monthand Point of Origin (Ocean Data Systems,Incorporated, 1973).

1

(5) Tropical Cyclones of the NorthIndian Ocean (Sadler and Gidley, 1973)ENVPREDRSCHFAC Tech Paper No. 2-73.

(6) The Typhoon Analog ComputerProgram (TYFOON) described in the 1972Typhoon Analog Program (TYFOON-72).

b. EXTRAPOLATION :

Extrapolation of storm movementusing 12-hour mean speed and direction wasthe most reliable objective method for both24- and 48-hour forecasts. Forecasts aredetermined by simple linear extrapolationusing the 12-hour old best track positionand the current warning position.

c. OBJECTIVE TECHNIQUES:

During 1973, the following objec-tive forecasting methods were employed:

(1) ARAKAWA - Regression forecastsderived from surface pressure grid values.

(2) MOHATT (Modified HATRACK) -Steering by geostrophic winds derived fromsmoothed height fields at 850-mb and 700-mblevels modified by 12-hour history inputs.

(3) TYMOD - Program selects beststeering level using global band upper airfields (GBUA) from FLENUMWEACEN Montereymodified by 12- or 24-hour history inputs.

(4) TYFOON - Analog weighted meantrack.

4. FORECASTING PROCEDURES

a. TRACK FORECASTING:

An initial track based on persis-tence blended subjectively with climatolo-gy is developed for a 3-day period. Thisinitial track is subjectively modified bythe following:

(1) Recent steering is evaluatedby considering the latest upper air anal-yses as representative of the average upperair flow over the past 24 hours. (Thelatest upper air analyses are about 12hours old, thus roughly representing themid-point of the last 24-houT time inter-val) . By this technique, actual Past 24-hour movement serves to indicate the beststeering level as well as the effectivenessof steering.

(2) Objective techniques are con-sidered, with the techniques being rankedaccording to their past performance onsimilar storms.

(3) Twenty-four hour height changeanalyses are evaluated for forecast track/speed changes (Hoover, D~vices for Fore-casting Movement of Hurrlcances, Manuscriptof U.S. Weather Bureau, 1957).

(4) The prospects of recurvatureare evaluated for all westward movingstorms. The basic requisites for thisevaluation are accurate continuity on mid-Iatitude troughs and numerical progs toindicate changes in amplitude or movement.Relative position and strength of the sub-tropical ridge and northward tendency due

to internal forces are also importantconsiderations.

(5) Finally, a check is madeagainst climatology to ascertain the like-lihood of the forecast. If the forecasttrack is climatologically unusual, a re-appraisal of the forecast rationale isconducted and adjustment made if warranted.

b. INTENSITY FORECASTING:

For intensity forecasting, heavyreliance is placed on short term trends,climatology, and the satellite interpreta-tion model developed by Mr. Vernon Dvorakof the National Environmental SatelliteService. After these initial inputs,further factors considered are upper ttopo-spheric evacuation and possible terraininfluence.

5. WARNINGS

Tropical cyclone warnings arenumbered sequentially. If warnings arediscontinued and the storm reintensifies?as Typhoons Dot, Ellen, and Patsy did thisyear, warnings are numbered consecutivelyfrom the last warning issued. Amended orcorrected warnings are given the samenumber as the warnings they modify plus asequential alphabetical designator to in-dicate it is an amended warning. Forecastpositions are issued at 00002, 06002,1200Z, and 1800Z. The forecast periods are12-hr and 24-hr for tropical depressionsand 12-hr, 24-hr, 48-hr, and 72-hr fortyphoons and tropical storms.

Forecast periods are stated withrespect to warning time. Thus , a 24-hourforecast verified 26 1/2 hour after theaircraft fix data, 30 hours after thelatest surface synoptic chart, and 30 or36 hours after the latest upppr air charts.

Warning forecast positions are ver-ified against the corresponding post anal-ysis “best track’ Positiens. A summary of

results from 1973 is presented in Chapter V.

6. PROGNOSTIC REASONING MESSAGE

Whenever warnings on typhoons and trop-ical storms are being issued, a prognosticreasoning message is released at 0000Z and12002. This message is intended to providethe field meteorologist with the reasoningbehind the latest JTWC forecasts.

7. TROPICAL WEATHER SUMMARY

This message is issued daily from 1 Maythrough 31 December and otherwise whentropical cyclone formation is forecast orobserved. It is issued at 0600Z and de-scribes the location, intensity, and like-lihood of development of all tropical lowpressure areas including upper tropo-spheric lows and significant cloud massesdetected by satellite.

8. TROPICAL CYCLONE FORMATION ALERT

Alerts are issued when the format~~s;fa tropical cyclone is anticipated.messages are issued as required and arevalid for up to 24 hours unless cancelled,superse~ed, or extended.

2

CHAPTER II – RECONNAISSANCE & COMMUNICATION

1. GENERAL

The Tropical Cyclone Warning Servicedepends on reconnaissance to fix the loca-tion and determine the intensity of tropi-cal cyclones. Due to the vastness of thewarning area and the scarcity of reportingstations, land and ship reports are notsufficient for these determinations. Inthe past, aircraft reconnaissance was usedalmost exclusively to determine positionand intensity. With the increasing satel-lite capability during the last severalyears, satellite derived data have assumedgreater importance. During the past seasonDefense Meteorological Satellite Program(DMSP) data were used for positioning andintensity estimates approximately one-Eourth of the time.

2. RECONNAISSANCE RESPONSIBILITY ANDSCHEDULINGAircraft weather reconnaissance is per-

formed in the JTWC area of responsibilityby the 54th Weather Reconnaissance Squadron(54 WRS). The squadron, equipped with nineWC-130 aircraft, is located at Andersen AirForce Base, Guam. The JTWC reconnaissancerequirements are sent daily to the TropicalCyclone Reconnaissance Coordinator. Theserequirements include areas to be investi-gated, forecast position of cyclones to befixed, and standard synoptic tracks to beflown.

Four fixes per day, at six-hourly inter-vals, are required (CINCPACINST 3140.lL) onall significant tropical cyclones in theJTWC primary area of responsibility [seeinside front cover). Two fixes per day arerequired in the secondary area. During thepast season, extensive use was made of theSelective Reconnaissance Program (SRP) tofulfill these requirements.

The SRP was implemented in 1972 to alle-viate pressure on overtaxed aircraft recon-naissance assets. The SRP attempts to op-timize the entire reconnaissance system byusing each reconnaissance platform (air-craft, satellite, and surface radar) underoptimum conditions whenever possible. Va-rious factors are considered in selectingwhich reconnaissance platform to use forany warning, e.g. , the cyclone’s locationand stage of development, the DMSp satel-lite times and areal coverage, availabilityof land radar reports, the cyclone’s threatto specific U.S. interests, aircraft oper-ational limitations (e.g., one fix versustwo fix missions), etc.

Aircraft reconnaissance .continues tobe the best method for determining tropicalcyclone position, intensity, and structure(i.e., radius of wind speeds of various in-tensities). Only the aircraft can providedirect measurements of height, temperature,and wind at flight altitude, sea levelpressure, and other parameters. The air-craft also provides much greater flexibili-ty In time and space compared to the otherplatforms. DMSP satellites provide day andnight coverage of the JTWC area of respon-sibility. DMSP satellite imagery provides

estimates of cyclone positions and, for day-time passes, estimates of intensities usin~the Dvorak technique (NOAA TECHNICAL MEMO-RANDUM, NESS-45). In addition, satellitedata used in conjunction with conventionaldata can provide estimates of the radii ofvarious wind speeds. The primary disadvan-tages of satellites is that the coverage isoften not timely for warning purposes andthe satellite provides no direct measure-ments of parameters closely related to tro-pical cyclone intensity. Land radar pro-vides useful positioning data when tropicalcyclones are located near the Republic ofthe Philippines, Hong Kong, Taiwan, or Japan(including the Ryukyus or other islands).It does not, however , provide measurementsor estimates of tropical cyclone intensityor structure. The following sections sum-marize the JTWC utilization of the variousreconnaissance platforms during 1973.

3. AIRCRAFT RECONNAISSANCE EVALUATIONCRITERIAThe following criteria are used to eval-

uate aircraft reconnaissance support to theJTWC .

a. Six-Hourly fixes - To be counted asmade on time, a fix must satisfy the fol-lowing criteria:

(1) Made not earlier than 1/2 hourbefore to 1 hour after scheduled fix time,

(2) Aircraft in area requested byscheduled fix time, but unable to locate acenter due to:

(a) Cyclone dissipation; or

(b) rapid acceleration of thecyclone away from the forecast position.

(3) If penetration not possible dueto geographic or other flight restriction,radar fixes are acceptable.

b. Levied 6-Hourly fixes made outsidethe above limits are scored as follows:

(1) Early - fix made within theinterval from 3 hours to 1/2 hour prior tolevied fix time. No credit given for earlyfixes made within 1 1/2 hours of the pre-vious fix.

(2) Late - fix made within the in-terval from 1 hour to 3 hours after leviedfix time.

c. When 3-Hourly fixes are levied,they must satisfy the time criteria ofparagraph one in order to be classified asmade on time. Three-Hourly fixes made thatdo not meet the above criteria are classi-fied as follows:

(1) Early - fix made within theinterval from 1 1/2 hours to 1/2 hour priorto levied fix time.

(2) Late - fix made within the in-terval from 1 hour to 1 1/2 hours afterlevied fix time.

3

d. Fixes not meeting the criteria of,paragraphs one, two, and three arescored as missed. Requirements levied withless than 24 hours notification, if missed,are counted as unfulfilled. If the squadronis in an alert posture, the fix is scoredas missed vice unfulfilled.

Levied fix time on an “as soon asposs;ile” fix is considered to be:

(1) Sixteen hours plus estimatedtime enroute after an alert aircraft andcrew are levied; or

(2) Four hours plus estimated timeenroute after the DTG of the message levyingaTASAP fix if an aircraft and crew, pre-viously alerted, are available for duty.

f. Investigatives - To be counted asmade on time, investlgatives must satisfythe following criteria:

(1) Aircraft must be within 250nmof the levied investigative point by thespecified time.

(2) The specified flight level mustbe flown.

(3) Reconnaissance observations arerequired every half-hour in accordance withAWSM 105-1. Turn and mid-point winds shallbe reported on each full observation whenwithin 250nm of the investigative point.

(4) Observations are required inall quadrants unless a concentrated inves-tigation in one or more quadrants has beenspecified.

(5) Specified investigative trackmust be flown.

(6) Aircraft must contact JTWC be-fore terminating the investigative.

!3. Investigatives not meeting the timecriteria of paragraph f. will be classifiedas follows:

(1) Late - aircraft is within 250nmof the investigative point after the speci-fied time, but prior to the specified timeplus 2 hours.

(2) Missed - aircraft fails to bewithin 250nm of the investigative point bythe specified time plus 2 hours.

h. Requirements levied as “resourcespermitting” are not evaluated.

4. AIRCRAFT RECONNAISSANCE SUMMARY

There were 362 required six-hourlyfixes in 1973, representing a record lowsince establishment of the JTWC. Of the362 required fixes, 227 or 62.4% were le-vied upon aircraft. The remaining requiredfixes were satisfied by satellite, radar,extrapolation, or synoptic data. The SRPmade it possible, when there was a choicebetween aircraft, radar, or satellite, toreduce the aircraft levy. By employingSRP, 45 fixes were levied upon satellite orradar, a savings of 16.5% in the use ofaircraft. In addition to the 227 fixes, 28investigatives were also levied on aircraft.

This total aircraft levy is only 38% of theaverage levy from 1965 through 1973. Themean deviation from the best track for allaircraft fixes was 16nm. This is a 2nm de-crease from the average deviation for thepast 3 years.

The total of 227 fixes levied does notinclude intermediate fixes , which averaged131 for the past two years. The decreasein the number of intermediate fixes -- 182in 1971, 81 in 1972, and none in 1973 --and investigative -- 179 in 1971, 81 in1972, and 28 in 1973 -- during the pastthree years resulted from a CINCPAC requestto reduce intermediate fixes and the appli-cation of the DMSP satellite data (Section6).

Table 2-1 summarizes reconnaissance ef-fectiveness. Using the scoring criteria inSection 3, the 13 missed plus unfulfilledfixes, or 5.7% of the total levied fixes,represent a significant decrease from theprevious two year average of 13.9%. Thepercentage of late and early fixes rosefrom 10.6% in 1972 to 15.3% in 1973.

4BLE 2-1. AIRCRAFT RECONNAISSANCE?FECTIVENESS

NUMBEROFLEVIEDFIXES PERCENT

,mpletedon time 179 79.0

rly 4 1.7

te 31 13.6

ssed 11 4.8

fulfilled 2 0.9

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LEVIEDVS. MISSEDFIXES

LEVIED MISSED PERCENT—— —

‘ERAGE1965- 1970 507 10 2.0

1971 802 61 7.6

1972 624 126 20.2

1973 227 13 5.7

Figure 2-1 relates the number of fixesmissed/unfulfilled to the monthly fix re-quirements and multiple-storm days, ~.e. , aday when two or more storms were active atthe same time. The 82 levied fixes in Oc-tober account for 36% of the total leviedfixes. October also included 42% of themultiple storm days and 30% of the missedfixes as compared to August which had 22%of the storm days, but 46% of the missedfixes. August, however, had only 21% ofthe levied fix requirements.

Figure 2-2 compares the percentage offixes and investigatives missed/late versusthe number of storms per day. The 26 dayswith 2 or more storms represents only 35%of the calendar days of warning; however,they encompass 7S% of the mjssed/late fixesand investigatives. This indicates, thateven in a light season, concurrent stormscan overtax current aircraft reconnaissancecapabilities.

F

.

4

5. RADAR RECONNAISSANCE SUMMARY

A total of 419 radar reports of tropi-cal cyclones were received during the 1973season, 409 from land stations, 3 fromships, and 7 from aircraft. This is a sig-nificant decrease from 1972 when over 700radar reports were received. There are twoprimary reasons for this decrease, the largedecrease in tropical cyclone activity from1972 to 1973 and the significant reductionof military activities in the western NorthPacific and South China Sea areas,

To evaluate the 1973 data in terms ofquality, the land radar reports receivedwere grouped into three accuracy categories,a method provided for in the WMO code. Thecategories used are defined as good (lessthan 6nm), fair (6-20nm), and poor (greate”rthan 20nm). Using this stratification, 32%of the reports were classified as good, 40%as fair, and 28% as poor. In addition tothe above accuracy classifications whichare derived from the radar operations, allland radar reports were compared to theJTWC best track positions and deviationscomputed. The mean deviation was 12nm, a29% decrease fron the average of 17nm forthe previous three years.

The radar sites that provide some ofthe most significant coverage to JTWC arethose whose surveillance borders within theAir Weather Service no-fly zone. The RoyalObservatory at Hong Kong provided valuablepositioning information on 7 tropical cy-cyclones during 1973 in which geographicalrestrictions existed to reconnaissance air-

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craft. Other locations which play similarroles are those situated on western Taiwanand Korea, although by the time a tropicalcyclone reaches the latitude of Korea itsradar presentation is often quite deterio-rated. A key station for tracking tropicalcyclones in the northwestern South ChinaSea during the Vietnam conflict was theMonkey Mountain site at Danang. The lossof observations from this site last seasonproved quite critical during typhoon Ani-ta’s trek into the Gulf of Tonkin this pastJuly, adversely affecting units of the 7thFleet .

The receipt of land radar reports fromnational meteorological and AC6W sites inthe Republic of the Philippines was greatlyimproved in 1973 compared to previous years.This improvement is attributed to recentimprovements in the radar network, bettercommunications , and closer liaison betweenU.S. military and Philippine officials.

Of 17 tropical cyclones which came with-in the surveillance range of the Far Eastradar networks, four typhoons Ellen,Billie, Nora, and Dot accounted for the na-jority of radar reports. Each of thesestorms was characterized during periods ofobservation by slow movement allowing for .,numerous position reports. Billie whilepassing through the southern Ryukyus wasunder coverage of 6 radars simultaneouslyfor a 12 hour period. Radars of NationalMeteorological Services accounted for 70%of the 419 observations received at theJTWC for tropical cyclones during 1973.AC6W sites furnished 23% and Air WeatherService radars, contributed 8%.

5

6. SATELLITE RECONNAISSANCE SUMMARY

Satellite reconnaissance information isprovided to the JTWC by the Air Force De-fense Meteorological Satellite Program(DMSP) site collocated with the JTWC. Thissite was established in May 1971. Duringthe 1971 storm season, DMSP data were avail-able to the JTWC forecasters but were notauthorized by CINCPAC as a substitute foraircraft fixes. Coincident with the site’sestablishment was the implementation of aTechnique Development Program (TDP) de-signed to determine the potential of DMSPdata as an alternative reconnaissance plat-form. This was necessary as aircraft re-sources were being reduced and it was pos-sible that the remaining reconnaissancefleet would be subject to further reduc-tions. Hence the SRP concept was intro-duced. Under the SRP, the JTWC would se-lectively levy reconnaissance requirementson aircraft, high resolution satellites andland radar with the satellites expected tofulfill an increasingly important role.

By the end of 1971, the TDP had estab-lished the viability of satellite derivedstorm positions and intensity estimates.Plans were then made to implement the SRP.During 1972, techniques used to positiontropical cyclones and estimate their inten-sities from DMSP data were further refined.An organized approach to daily decisionmaking on the use of DMSP data in lieu ofaircraft was implemented beginning with Ty-phoon Phyllis in July 1972. Factors suchas satellite coverage of the storm, timeli-ness of the DMSP data, and quality of theposition were considered in this decisionprocess. During the remainder of 1972, sa-tellite fixes were levied in lieu of air-craft 12% of the time. During 1972, theGuam site provided the majority of satel-lite data used operationally by the JTWC.Data were received from other Pacific DMSPsites and the Air Force Global Weather Cen-tral (AFGWC) but there was no formal pro-gram to rely on these data.

Prior to the start of the 1973 season,an SRP network was established consistingof Guam; Fuchu, Japan; and Nakon Phanom(NKP), Thailand (primary sites); and.Kadena,Okinawa; Osan, Korea; and AFGWC serving asbackup sites. The network was designed toprovide timely DMSP data to the JTWCthrough the Guam site which served as clear-ing house and quality control monitor. TheGuam site was also responsible to the JTWCfor forecasting which of the primary sitesor combination of sites would receive us-able fixes. Regardless of whether suchfixes were levied in lieu of aircraft, thesites affectea would be notified by messageto pass the required information to theJTWC . As the data were received, processed,and analysed, data were first passed byphone to the Guam site and followed up bymessage to the JTWC.

There are six position classes referredto by Position Code Numbers (PCN). The PCNidentifies the method of gridding and thetype of circulation center; it-also has as-sociated with It a set of statistics re-lated to its accuracy. Table 2-2 providesthe methods of center determination andgridding for each PCN. The mean error,

standard vector deviation, and sample sizeare given for the 3 major classes i.e. eye,well-defined circulation center, and poorly-defined circulation center. While no sta-tistically significant difference presentlyexists between geographical and ephemerisgridded positions, it was decided to retainthe gridding method as part of the PCN stra-tification to provide a check on the accur-acy of ephemeris gridding and to isolateany problems growing out of either geogra-phical or ephemeris gridding in the future.

TABLE 2-2. GUAM DMSP SITE TROPICALCYCLONE POSITIONING STATISTICS, 1973(1972)

& “EIHOD‘F C=’TERDETEmfTVATIOX/GRrDDIh~

I

The 1972 figures which serve as the stan-dard are given Tn parentheses. Table 2-3shows corresponding 1973 figures for NKPand Fuchu respectively. Only PCN’S of 1throtuzh 4 are considered as quality fixes,i.e. ~ocation accuracy comparable on theaverage to that expected from the aircraft.It should be noted that only 31% of the po-sitions made during 1973 by the primaryDMSP sites were of PCN’S 5 or 6, a signifi-cant reduction from 1972 when 50% of thepositions were classified in the poorly de-fined category.

With only one operational satelliteduring the early part of the 1973 season(July and August), satellite coverageduring the period S 1/2 hours before to 1/2hour after warning time was available for52% of the warnings. However, during thelast part of the season (September, October,and November) with two functional satel-lites, 87% of the warnings had satellitecoverage available during the same time

TABLE 2-3. DMSP TROPICAL CYCLONEPOSITIONING STATISTICS 1973

NAKON PHANOM, THAILAND

MEAN STANDARD VECTOR SAMPLEPCN ERROR (NM) DEVIATION (NM) SIZE

l&2 16.8 20.0 47

364 19.1 25.4 62

566 48.1 66.3 85

FUCHU, JAPAN

MEAN STANDARD VECTOR SAMPLEPCN ERROR (NM) DEVIATION (NM) SIZE

162 15.4 17.7 37

3G4 20.9 25.0 75

5&6 36.2 51.4 26

v

6

period. For 24% of the 390 warnings issuedby the JTWC, both satellite coverage andtimeliness of the data were met simultane-ously. In this context, timeliness is de-fined as having DMSP satellite data withnodal times of 1 1/2 to 3 hours (descendingnode) or 1 3/4 to 3 hours (ascending node)prior to warning time. When quality PCN’Sare also stipulated, it was found that foronly 14% of the warnings were coverage,timeliness, and quality PCN forecast tooccur. When the three criteria given aboveare anticipated, the forecast is referredto as SRP quality. The verification ratefor SRP quality forecasts during the seasonwas 90%. The actual use rate of satelliteas the basis for warnings was considerablylarger than the 14% which were forecast tobe of SRP quality. Altogether, 27% of theJTWC warnings were based on satellite data.Of the forecast SRP quality fixes, 25% werelevied equating to 13% of the satellitefixes used for warnings. The remaining 87%of the satellite fixes for warnings con-sisted of non-SRP quality and some addi-tional SRP quality which were forecast, notlevied, but subsequently used. A summaryof these SRP statistics is given in Table2-4.

There were a wide variety of satelliteproducts available from the SRP networkduring the 1973 season both for real-timeanalysis by the individual sites and post-analysis conducted by the Guam site and theJTWC . Historically, the types of data from

TABLE 2-4. SELECTIVE RECONNAISSANCEPROGRAM SUMNARY

PARAMETERS RATIO PERCENT

Numberof caseswhere therewas DMSP coverage of sterm=a timelinessfor use inwarninE/totalnumberofwarningsissued 95/390 24

Numberof caseswhere therewas coverageof storm,timelinessof data,andPCN : 4 [SRPQualityforecastsmade)ftotal~me: of warning

S6/390 14

Numberof SRP qualityforecastslevied/numberofSRP qualityforecastsmade 14/s6 25

Numberof SRP qualityfore-castsused as basis forwarnings/numberof warningsbased on satellite 14/107 13

Number of warningsbased onsatellite/totalnumberofwarningsissued 107/390 27

TABLE 2-5. DMSP IMAGERY DATACHARACTERISTICSPARAMETER VISUAL INFRARED

VHR HR WHR IR

Resolution[nauticalmiles) 0.33 2.0 0.s 2.0

Bandwidth(micrometers) 0.4-1.1 0.4-1.1 8.0-13.0 8.0-13.0

Equivalentblackbodytemperature(.~~~~in) 217-307 210-310

the DMSP satellites have remained essential-ly unchanged during the past three years.Satellite meteorologists at the SRP networksites had available Very High Resolutiondaytime and nighttime infrared (WHR), andHigh Resolution daytime and nighttime vis-ual (HR) and infrared (lR). Table 2-5 pro-vides the imagery data characteristics.

During daytime, VHR along with IR arethe primary data used for positioning andintensity analysis, In addition, visualand IR data enhancement techniques havebeen developed which often permit the ana-lyst to locate the circulation center whenthe primary data alone would result in apoorly defined center. Likewise, nighttimeposition can often be classified as eyefixes or well defined centers as a resultof having HR data from moonlight available.Marginal eye centers or well defined cen-ters not visible on WHR can frequently bedetermined with as little illumination asthat provided by a half-moon.

Satellite data are playing an increas-ingly larger role in tropical cyclone re-connaissance. For example, the operationaluse of MISP data has produced a significantdecrease in the number of aircraft investi-gative flights flown. For the two yearspreceding the establishment of the SRPnetwork (1970 - 1971), the ratio of inves-ti~ative flights flown to the number ofstorms was 5.5:1, while for 1973 this ratiowas reduced to 1.2:1.

7. COMMUNICATIONS

a. AIR TO GROUND

Aircraft reconnaissance data arenormally received by the JTWC via directphone patch through Andersen, Clark, orFuchu aeronautical stations. Under de-graded propagation conditions, data can beintercepted by a weather monitor locatednear these stations and relayed by AUTOVONor teletype to the JTWC.

Average communications delays forthe preliminary and complete center datamessages for past years are compared with1973 delays in Figure 2-3. Delay times aredefined here as the difference between thefix time and the time of message receiptat the JTWC. The preliminary fix messagewas introduced in 1972 to reduce delays inthe receipt by the JTWC of vital positionand intensity information. After two yearsof use, it has proved its effectiveness andpermits a significant amount of extra timeto be spent in forecast preparation. The48 minute average delay in the completecenter data message during 1973 shows anincrease of about 14 minutes over 1972.This increase is attributed to several cir-cumstances which prevailed during the 1973season: (a) more emphasis was placed uponreceipt of the preliminary message during1973, lessening the need for passing thecomplete center message to the JTWC asquickly as before, (b) messages were morecarefully prepared, and (c) a larger shareof the messages were passed through Clarkaeronautical station than in previousyears due to location of cyclone tracks.This routing of phone patches throughClark places more stringent requirementson radio-telephone quality and has been

7

I ,

EJa9 =m 1971 m 1973

YEAR

FIGURE 2-3. DELAY TIMES - Rtct2.iP~ o~age data meb~ugc.

noted in previous years to result in longerdelays than a direct phone patch throughAndersen aeronautical station.

Table 2-6 depicts the complete cen-ter data messages received over one hourafter fix time and after warning time. Thegrowth of the percentages in 1973 can bepartially attributed to the above mentionc~reasons and the increase in the percentageof late fixes (section 4). Nevertheless,only 3% of the messages were delayed morethan 80 minutes.

TABLE 2-6. 1973 AIR/GROUND DELAYSTATISTICS FOR AIRCRAFT RECONNAISSANCECOMPARED WITH PREVIOUS YEARS

1967 1968 1969 1970 1971 1972 197.3—— —. —

$ COUPLETEFIXMESSAGESDELAYED 16 4 3 s 6 6 20OVER ONE HOUR

t COMPLETE FIXMESSAGESRECEIVED 3.1 0.7 0.6 0.9 2.1 5.s 10.1AFTERWARNINGTIME

b. SELECTIVE RECONNAISSANCE PROGRAM

With the advent of the SRP. the im-portance of radar and satellite fi~ datahas increased from previous years; there-fore, a review of the associated communi-cations delays follows. A sampling of ra-dar messages resulted in a considerablevariation of receipt delays. Delay timesare defined as the differences between theobservation time and the time of messageentry into the AWN. Several sources wereconsistently associated with small delaytimes , while the receipt time of otherswere highly erratic. AC6W radar site datafrom the Republic of the Philippines werenormally received within 35 minutes. Datafrom nationally operated radars of theRepublic of China, Hong Kong, Japan, andRepublic of the Philippines were delayed20 to 50 minutes depending on country oforigin. In the wbrst cases, the JTWC stillreceived the messages within 90 minutes ofobservation time. Tropical cyclone radardata is routed to the JTWC over the AWNthrough the use of a special high prece-dence collective indicator. Additionally,the AC&W radar messages were phoned to theJTWC from Clark AB, thus providing the in-formation somewhat earlier than indicated.

Over 75o position and intensityestimates were derived from Air WeatherService (AWS) DMSP sites and the aircraftcarrier CONSTELLATION during 1973. The da-ta from the AWS DMSP sites were immediately

passed by AUTOVON followed by an AWN mes-sage. AUTOVON provided rapid communicationof the essentials and a brief two-way dis-cussion of the data (a benefit not possiblewith message). Average delay times of 51minutes for telephone and 83 minutes formessage resulted from a sampling of thelast six storms. These delay times are thedifference between satellite equator-cross-ing time and the time of the telephone callor-entry of the message into the AWN. sys-tematic differences in data processing timeamong the DNSP sites introduces small var-iati~ns in the above figures which arc in-dependent of communications and analysistime. However, it is important to note,that on the average, the data were avail-able to the JTWC within one hour afterequator-crossing time.

c. OUTGOING COMMUNICATIONS

Messages originating at the JTWCare handled by the hTimitzHill MessageCenter Naval Communications Station, Guam(NHMC). By special agreement, typhoon andtropical stcrm warnings are placed in thecommunications system before pending imme-diate precedence traffic. Manual process-ing is accomplished as though the warninghad flash precedence. Tropical depressionwarnings are normally handled as immediatemessages. Warnings were delivered to themessage center an average of 23 minutes be-fore warning time (Figure 2-4). Yearlyaverages of the parameters described areplotted relative to warning time. Thelength of the vertical bars represents theaverage difference between the time typhoonand tropical storm warnings were passed tothe NHMC and the time of transmission.Note that the handling time decreased from31 minutes in 1972 to 15 minutes in 1973.Handling times for tropical depressionwarning (not shown) were reduced from S1minutes in 1972 to 2S minutes in 1973.

The dramatic improvement in han-dling time during 1973 allowed the averagemessage to be placed in the circuits beforethe established warning time. This was amajor improvement over the previous twoyears when the average message left Guammore than 10 minutes after warning time.The reduced handling time can be attribut-ed primarily to rectification of problemswithin the NHMC itself. The time of re-ceipt of a warning at a particular stationdepends on factors beyond the control ofboth the JTWC and the NHMC.

FIGURE 2-4. AUTOV7N handling -Lime data~ofi-typhoon and txop.icalb-totmNJUhkI~n9A.

w

8

CHAPTER Ill — RESEARCH SUMMARY

1. GENERAL

In past years, technical notessummarizing research studies made by theJTWC personnel were included in the AnnualTyphoon Reports (ATRs). In this and futureATRs, however, only brief synopses of thesestudies will be given. The complete stud-ies will be published separately asFLEWEACEN/JTWC Technical Notes. It is feltthat this procedure offers several advan-tages. First, it allows the administrativeworkload associated with publication pre-paration to be distributed throughout theyear rather than concentrated within a fewmonths during preparation of the ATR.Second, it allows authors to include moretechnical details of their studies thanwo@d be appropriate for inclusion in theATR.

2. INVESTIGATION OF GUST FACTORSIN TROPICAL CYCLONES

(Reference: Atkinson, G.D., FLEWEACEN/JTWC Technical Note 74-l).

The 1972 Tropical Cyclone Confer-ence requested that FLEWEACEN/JTWC includepeak gusts in the warnings when sustainedsurface wind speeds equal or exceed 50 kts.During 1972, a sustained wind/peak gustgraph derived by former JTWC personnel wasused. Details on how this graph was de-rived were not available and there was ageneral feeling among JTWC forecasters thatthe gust factors derived from this graphwere too high for open water conditions.Therefore, at the 1973 Tropical CycloneConference, FLEWEACEN/JTWC requested thatall 7th Fleet ships equipped with anemo-meters include peak gusts as well as sus-tained winds in their weather reportsduring strong wind conditions. These shipobservations and a comprehensive literaturesurvey led to the derivation of a new sus-tained wind/peak gust relationship whichwas introduced into operational use by theJTWC during the 1973 season. This studyshowed that for strong wind conditions,gust factors (i.e., ratio of peak gusts toone-minute average sustaitiedwind speeds)over open water should fall in the rangeof 1.20 to 1.25. Based on these results,the sustained wind/peak gust relationshipsshown in Table 3-1 are now used operation-ally by the JTWC.

TABLE 3-1. JTWC SUSTAINED l-MINUTE WIND-PEAK GUST (KNOTS) RELATIONSHIPS

WIND(GUST) WIND(GUST) WIND(GUST)

50(65) 95(115) 140(170)55(70) 100(125) 145[175)6oi75j lo5(130j lso(180j65(80) 110(135) 155(190)70(85) 115(140) 160(195)75(90) 120(145) 165(200)80(100) 125(150) 170(205)85(105) 130(160) 175(210)90(110) 135(165) 180(220)

3. INTENSITY FORECASTING USING THETYFOON ANALOG COMPUTER PROGRAM

(Reference: Craiglow, L.H., Jr., FLEWEACEN/JTWC Technical Note 74-2).

The computerized TYFOON analogprogram has been used by the JTWC as anaid in forecasting tropical cyclone move-ment since 1970. This study investigatedthe usefulness of the TYFOON program forforecasting tropical cyclone intensitiesat 24-, 48-, and 72-hours. It modifiedand extended a previous study on this sub-ject by former JTWC personnel. Three pa-rameters which are available on the basicclimatological data tape used in theTYFOON program were selected to determinetheir usefulness in intensity forecasting.These are the minimum sea level pressure,the 12-hour change in minimum sea levelpressure, and the maximum sustained sur-face wind speed. Based on selected valuesof these criteria, current and analog trop-ical cyclones were separated into twoclasses (deepening or weakening) and analogforecasts were computed. During the test-ing, several changes were made to the clas-sification criteria to obtain better re-sults. Also, it was determined that in-tensity forecasts computed independentlyfor the various time periods were not con-sistent. Therefore, the program was modi-fied so that each succeeding intensityforecast used the previous intensity fore-cast as an input, ,i.e., initial conditionsfor the 48-hour forecast would depend onthe 24-hour forecast, etc. Verificationresults based on selected cases from the1972 tropical, cyclone season showed theanalog program produced intensity forecaststhat were slightly better than the officialJTWC forecasts for the 24-hour period butwere slightly worse than the official fore-casts at 48 and 72 hours. Nevertheless,these preliminary results indicate thatfurther testing of this program is warrant-ed to provide another objective forecastaid to JTWC forecasts.

4. EVALUATIONOF THE EXTRAPOLATIONFEATURE OF THE TYFOON ANALOGCOMPUTER PROGRAM

(Reference: Craiglow, L.H., Jr., FLEWEACEN/JTWC Technical Note 74-3).

The original version of the TYFOONanalog program, first used operationally bythe JTWC in 1970 has been modified severaltimes to improve its performance. In theTYFOON-72 version of the program, if a se-lected analog storm had insufficient posi-tions to provide a forecast out to 72hours, the program extrapolated up to fouradditional six-hourly positions. This ex-trapolation feature was necessary becauseof premature termination of many tropicalcyclones on the original data tape (1945-1969). During 1972, tropical cyclone datafor 1970 and 1971 were added to the basicclimatological data tape and tracks for alltropical cyclones for the entire period ofrecord (1945-1971) were extended. Thesemodifications to the data tape and reduc-tions of the basic time interval for selec-tion of analog cases from *5O days to *35days resulted in the version of the TYFOON

9

program known as TYFN 73. Since the origi-nal tropical cyclone tracks were subse-quently extended, it was felt that the ex-trapolation feature of TYFOON-72 was nolonger required. To test this hypothesis,15 cases from 1972 were selected and 24-,48-, and 72-hour position forecasts wereprepared using both TYFOON-72 and TYFN 73.The overall results showed the averageforecast errors for TYFN 73 were slightlylower than TYFOON-72 at all time periods.The most significant fact, however, wasthat TYFN 73 required 46% less computertime on the average than TYFOON-72. Con-sidering that the JTWC requires hundreds ofanalog forecasts each year, the savings incomputer time will be significant. TheJTWC will use the TYFN 73 version of theanalog program during the 1974 tropicalcyclone season.

5. A COMPARISON OF THE SENSITIVITYOF TWO SIMILAR OBJECTIVEFORECAST TECHNIC)UES

(Reference: Craiglow, L.H. ,Jr., FLEWEACEN/JTWC Technical Note 74-4).

A number of computerized objectiveforecast techniques are available to assistthe JTWC in the preparation of warnings.Of concern is the sensitivity of thesetechniques to errors in the warning and his-tory positions. Two techniques; TSGLOB: de-veloped by FLEWEACEN Pearl Harbor, and It’ssuccessor, TYMOD, developed by FLEWEACEN/JTWC Guam, were chosen foT tt!Sting. Bothtechniques utilize the 24-hour global banduPPer air Progs (GBUA) provided byFLENU14WEACENMonterey. The 03/0000 GMT Jan-uary 1973 GBUA fields were chosen and a con-trol forecast for each technique was run onGuam’s CDC 3100 computer. Errors of sixand 12nm were introduced into the warningand history positions, both individuallyand collectively. Thirty-six cases wererun for TYMOD and 20 for TSGLOB the differ-ence being due to TYMOD having a 24-hourhistory position. The results showed thatTYMOD was less sensitive to positioning er-rors than TSGLOB. In addition, the TYMODerrors tended to reach a maximum about +48hours and then decrease in magnitude there-after. Finally, the test results suggestthat as much as 30% of the 24-hour Forecasterror may be caused by warning position er-rors.

6.INTERANNUAL VARIABILITY OF

RAINFALL AND TROPICAL CYCLONEACTIVITY IN THE WESTERN NORTHPACIFIC

(Reference: PTatte, J.F., FLEWEACEiN/JTWCTechnical Note 74-5).

In this study, rainfall amounts atvaTious stations in the tropical NorthPacific during the dry season (January-April) were correlated with the number oftropical cyclones occurring in the westernNorth Pacific area during the same year.The period of record used was 1959-1973.This period was selected because the JTWCwas established in 1959 and satellite co-verage of the tropics was available formost of this period. Therefore, it wasfelt that statistics on the number .of trop-ical cyclones would be highly reliable forthis recent period. Correlations were madefor each rainfall station individually andfor various groups of stations. Resultsindicate that the best correlation wasshown with rainfall on Guam (average ofthree Guam stations), however, the rela-tionship was poor (correlation coefficientof 0.24) and not sufficient for long-rangeforecasting purposes. The study also pro-vides a survey of various articles relatingtropical circulation patterns and rainfallto sea surface temperature anomalies andother large scale influences.

w

10

CHAPTER IV — SUMMARY OF TROPICAL CYCLONES

1. GENERAL RESUME

The western North Pacific remainedquiescent for the first six months of 1973before the first tropical cyclone devel-oped. Since World War IIZ only in 1952,when five months passed without a singletropical cyclone, has this area experiencedsuch a late start of the tropical cycloneseason (Table 4-l). According to statis-tics compiled by the Royal Observatory ofHong Kong, this dearth of tropical cycloneactivity during the first six months ofthe year has not occurred since 1917.Interestingly, on the average, fivetropical cyclones form during the firstsix months of the year of which threebecame typhoons.

The development of Tropical StormWilda on 1 July marked the beginning ofthe 1973 season. Within a span of 5months, a total of only 21 named tropical

cyclones developed, with 12 of these reach-ing typhoon intensity. Additionally, warn-ings were issued on two numbered tropicaldepressions. Typhoon frequency in 1973 wassignificantly lower than the yearly averageof 19 since the establishment of the JTWCin 1959. Only 1969 and 1970 experienced asimilar low frequency of typhoons duringthis period (Table 4-2).

In 1973, warnings were issued on only77 calendar days, approximately one halfof the 14-year average of 145 days. TheJTWC remained in warning status 62 daysless in 1973 than in 1972, an activetropical cyclone year.

Typhoon days for 1973 dipped to arecord low of 42 compared to 121 in 1972(Table 4-3). Based on the past 15 years,1973 was 54 days below the average and 20days beloh’ 1969 the next lowest. Thesefacts indicate that there was not only a

TABLE 4-1. FREQUENCY OF TROPICAL STORMS (INCLUDING TYPHOONS) BY MONTHS ANDYEARS

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOTAL

1945 000112 576130 261946 001012 323120 151947 001011 335661 271948 10 222 4321949 10 ; :015 : 2132 ;:

1950 000012 32; 1 181951 012111 : : 2 171952 :“ 00033 ;5634281953 0 !00122 63431231954 0 0 1 0 1 0 1 6 4. 3 3 0 19

1955 10 1 0 1 6 3 3 4 1 .1 221956 00 ;2 125523 1221957 2001 !11354 30211958 1 00135 3321221959 0 :11003 ;642226

1960 00 11 3 10 3 4 1 1 271961 11 ;13 ~54651 1311962 010120 673532 301963 000113 435 3 251964 000022 797 2 : 1 40

1965 221123 567221 341966 001 1587 2 1 301967 ? o 2 1 ;1687 ? 3 1 351968 000111 38:6:] 271969 101100 34 3 19

1970 010002 264540 241971 101342 46420351972 100 1 :54 2 301973 000 :0 ;752 :3 : 21

Totals 7 20 31 45 115 147 131 111 76 33 742Average .:: .24 .:; .69 1.07 1.55 3.97 5.07 4.52 3.83 2.62 1.14 25.59

\ )

.TABLE 4-Z. FREQUENCY OF TROPICAL STORMS REACHING TYPHOON INTENSITY BY MONTHSAND YEARS

JAN FEB MAR APR MAY JUN .TUL AUG SEP OCT NOV DEC TOTAL

1945 000001 253110 131946 001011 311947 00

1 2 0 130 103

1942:54119

10 80 ;1949

224121 1510000 !?33311 114

1950 000011 1213211951 012111 22312;;1952 : 000313 3432191953 0 !00112 42411171954 000010 144230 15

1955 101101 33211191956 001100 ;45131 1819s7 100111 253 0 181958 100013 :333 : 1 201959 000100 153322 17

1960 000102 280411 191961 001021 33 1 1 201962 000120 57 ; ; 3 0 241963 00 112 334 2

‘: o 2 219

1964 00 :353 ! 1 26

1965 100122 4 2 1 0 211966 000121 3 : ;201201967 001101 344330 201968 00 111143 540201969 10 ~10023 231013

1970 01 001 42310121971 00 :312 : 5 1 0 241972 100011 4 :3 ? 2 2 221973 000000 422400 12

Totals 8 2 6 17 24 75 103 93 84 52 22 517Avg .28 .07 .21 .59 .83 1?;7 2.59 3.55 3.21 2.90 1.79 .76 17.83

short period of typhoon activity (July toOctober) but also the short duration oftyphoons notably in August and September.The number of warnings issued totaled only390 which is S5% of the average over thepast 15 years. 1971 and 1972 could be con-sidered “normal” yeaTs compared to 1973since they were only slightly above theaverage with total number of warnings of747 and 739, respectively. 1973 was notwithout multiple storm occurrences with 27days with two or more cyclones and 9 dayswith three or more cyclones occurringsimultaneously (Table 4-4).

There were only three super typhoonsduring 1973, Billie, Nora, and Patsy,which is half of the climatological mean ofsix based on the past 1S years. This isnot surprising since most of the tropicalcyclones developed outside of the favorableareas for super typhoon occurrence delin-eated by Holliday (1970).

The 1973 season was marked by anotherpeculiarity. There was a pronounced ab-sence of tropical cyclone activity in thearea south of 20”N and east of 135°E which

cyclone development. Except for briefperiods during the summer months, the east-ward extension of the monsoon trough overthe western North Pacific Ocean was notice-ably missing. It was not until the latterhalf of the season that the monsoon troughbecame firmly established in the area tothe south of Guam when 3 successive ty-phoons were spawned during the first halfof October.

The Tropical Upper Tropospheric Trough(TUTT) was well established by mid-May. Itinitiated the development of Tropical StormClara in July and Tropical Storm Hope andTropical Depression No. 11 in August. Al-though the TUTT was in evidence throughoutthe typhoon season, the near-equatorialridge which normally forms to the south ofthe TUTT was absent except for brief peri-ods . Consequently, upper level westerliesprevailed over the Caroline and MarshallIslands, an area which would normally beunder deep tropospheric easterlies duringthe primary tropical cyclone season. Theresulting strong vertical wind shear overthe eastern Trust Territory was unfavorablefor tropical cyclone development.

v

is normally a favorable area for tropical

12

TABLE 4-3.

YEARm196019611962196319641965196619671968196919701971

JAN—------------------

2---------5

------2

___

TYPHOON DAYS 19S9-1973

FEB—---------------___---------------5

--—------

MAR .4PR MAY--- T ------ 2 ---

8 ------ :--- :5---- -- 7--- 25--- 5 112 7 ---

--- 61--- 5 ------- --- ----- 4 13*--- --- 1---- --- --

TOTALPER

10 13 36* ___ 23* 2* 12 98

2 10* 15 23* 17* 6 6 95--- 14* 37* 30* 19* --- 11915 11 23* 1:* 24* --- 11 1075* 27* 18* 28* 14 11* 6 111

1;* ~g* 23* 25* 14 6 --- 1087* 16* 23* 11 86

: 14* 10 32* 21* 2;* -:- 111768 32* 19 18* --- 97

___ 8 6 10 18 10* --- 62

25 24* 16 21* 6 --- 79

8 70* 27* 21* 11 7 --- 1111972 6 39* 16 16* 21 9 11 1211973 --- 11* 7* 4 20* --- --- 42

TOTAL 5 10 50 55 77 202 284 271 282 129 67 1441MEAN .: .3 .7 4.0 3.7 5.1 13.5 18.9 18.1 18.8 8.6 4.5 96.1

*Two typhoons occurring on the same day are counted as two typhoon days.

TABLE 4-4. SUMMARY OF JTWC WARNINGS 1969-1973

1960-1973(AVG) 1970 1971 1972 1973—_ __

TOTAL NUMBER OF WARNINGS 707 533 747 739 390

CALENDAR DAYS OF WARNING 146 127. 163 139 77

NUMBER OF WARNING DAYSWITH TWO OR MORllCYCLONES 52 29 54 46 27

NUMBER OF WARNINGS ”DAYSWITH THREE OR MORE CYCLONES 12 0 6 13 9

13

Based on available casualty reports,typhoons Nora and Ruth and tropical stormsSaTah and Vera accounted for the majoTityof the tropical cyclone related casualties.Taiwan, South Vietnam, and the Republic ofthe Philippines bore the brunt of the stormdamages and casualties. The Republic of thePhilippines was again, as in 1972, partic-ularly hard hit by the passage of Nora,Ruth, and Vera. The main Japanese islands,interestingly, did not experience coastalcrossing of a typhoon duTing 1973 which isa first according to available recordssince 1945.

Much of the pertinent meteorologicaldata and tropical cyclone damage statis-tics in this chapter weTe based on infor-mation received from the following

sources: Weather Bureau of the Republic ofChina; Royal Observatory of Hong Kong;Japan Meteorological Agency; NationalWeather Service of the Republic of thePhilippines; the Environm&ntal Data Service,National Oceanic and Atmospheric Adminis-tration and Casualty Returns, LiverpoolUnderwriters Association.

TABLE 4-5. LIST OF ESTIMATED CASUALTIESFOR THE 1973 SEASON

I TYPE NAME DEATHS MISSING— ——

I T DOT 1 -.T IRIST NORA 2; 4;T RUTH 27 23TS SARAH 50 --TS VERA 7S 58

total E E

NOTE : Only cyclones for which dataare available are listed.

TABLE 4-6. 1973 TROPICAL CYCLONES

CALENDAR MAXDAYS OF SFC

CYCLONE TYPE NAME (PRD OF WRNG) WARNING WINDt— .

01 TS WILDA 01 JUL-03 JUL 6002 TY ANITA 05 JUL-08 JUL ; 7003 TS CLARA 12 JUL-14 JUL 3 50i)4 TY BILLIE 13 JUL-19 JUL 7 13005 TY DOT * 606 TY ELLEN * 10 13:07 TS FRAN 29 JUL-30 JUL 2 4008 TY GEORGIA 09 AUG-12 AUG 409 TS HOPE 09 AUG-12 AUG 4 z:10 TY IRIS 10 AUG-17 AUG 8 85ii TD TD-11 13 AUG-14 AUG 2 3012 TS JOAN 18 AUG-20 AUG 3 4513 TS KATE 24 AUG-26 AUG 2 6014 TD TD-14 01 SEP-02 SEP 2 3015 TY LOUISE 03 SEP-07 SEP 516 TY MARGE 12 SEP-14 SEP 3 ;;17 TY NORA 02 OCT-10 OCT 9 160ii ii OPAL 04 OCT-08 OCT 5 7519 TY PATSY * 10 14020 TY RUTH 11 OCT-19 OCT 9 9021 TS SARAH 10 NOV-10 NOV 1 5522 TS THELMA * 4 5523 TS VERA 19 NOV-26 NOV 8 50

MIN WARNINGS’ISSUEDOBS NO. AS DIS’1”=SLP TOTAL TYPHOONS TRAVELED——

982 9 -- 384980 13 6 720998 -- 324916 2; 18 1560978 19 4 1020941 29 8 1092

1002 6 -- 330976 15 9 504996 15 -- 756972 30 16 1218

1005 6 -- 270990 10 -- 648983 -- 294NA : .-974 18 6 8?:964 12 4 792877 34 25 1584968 16 9 540893 34 14 1920957 33 23 2112984 4 -- 180991 13 -- 660990 28 -- 1134

1973 TOTALS 77** 390 142

*Dot 14/062 - 17/062 and 19/002 - 20/062 JULEllen 17/182 - 21/062 and 23/062 - 25/062 and 28/002 - 29/O~Z JULPatsy 06/062 - 12/122 and 13/122 - 15/062 OCTThelma 15/002 - 17/062 and 18/062 - 18/182 NOV

**OverlapPing days included only once in sum

t Over water estimate (one-minute averaging period)

DATA TAKEN FROM BEST TRACK

14

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18

2. INDIVIDUAL TYPHOONS

ANITA

Anita, the season’s first typhoondeveloped in the monsoon trough late on 5July under conditions quite similar tothose discussed by Ramage (1971). Severaldays prior to the initial development ofAnita, the low level southwesterly flowthroughout Indochina, the MalaysianPeninsula, and southern India increasedfrom an average of 10 to 20 knots tospeeds of 25 to 35 knots. The satellitemosaic on 4 July revealed that a band ofcloudiness extending from the Arabian Seato the South China Sea had increasedmarkedly in response to the intensifyingsouthwesterly flow (Figure 4-l).

Of particular interest during Anita’sinitial development were the strong winds(25 to 30 knots) extending more than 400nmfrom her center to the south with lighterwinds (10 to 1S knots) near the large anddiffuse center. These strong winds wereprimarily associated with the increasedmonsoon flow and not the storm itself,since Anita had not intensified suffi-ciently to produce the necessary pressuregradient to support such winds. Anitacontinued to exhibit this unusual windstructure as she intensified to typhoonstrength (Figure 4-2). The USNS WashoeCounty reported winds in excess of 35knots and mountainous seas over 150nm tothe south of Anita [06/0900 GMT). Early

on the 7th, a reconnaissance aircraftreported Anitars sea level pressure haddropped to 983mb with flight level andsurface winds of 50 to 80 knots within aband 30 to 60nm from the storm center,while winds within a 30nm radius of hercenter were 30 knots or less.

The storm initially drifted northnorth-west in response to a weakness in thesubtropical ridge to the north caused bythe remains of Tropical Storm Wilds. How-ever, by 1200 GMT, 7 July? significantheight rises at 500mb indicated the ridgewas reforming over southern China. As aresult, Anita assumed a more westerlytrack.

The USS OGDEN (LPD-5) reported eyepassage and greater than 60 knot winds(08/0000 GMT) near 17.5N 107.4E as herbarometer registered 981mb. The barographaboard the USS TRIPOLI (LPH-1O) recordedeye passage (08/0100 GMT) as the shipsteamed near 17.6N 107.2E (Figure 4-3).

A reconnaissance aircraft observed aminimum sea level pressure of 980mb and awell defined closed wall cloud indicatingcontinued intensification as the stormneared the North Vietnamese coast(08/1010GMT) . Anita reached peak intensity of 70knots prior to going ashore near Vinh,North Vietnam and quickly dissipated overland (Figure 4-4).

FIGURE 4-1. NOAA-2 bdd.~iie mobs.ic 60JL 3 JULY 1973 ~howing cLoud bandaAbocLated wi-ththe ~ou.thwebt monhoon exfending &tom the Aaabian Sea .tothe south China Sea. Remnanti o{ (Ui-Lcfa(A].

19

FIGURE 4-2. Taop.ical SXoam Anita neatityphoon -inzknbiiy 110 nm o~~.tha coat 06 the RepubL.ic o~ Vktnam, 7 JULY 1973, 0444 GMT.[OMSP imagwty)

4-3. RephoducZLon 04 Btiogfiaph ~hat~ &om the USS T’tipoLi [LPH-10)pubed -Wcough the eye o~ Typhoon An.Lta.

9

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20

FIGURE 4-4. Tgphoon AnLZa in the Gu16 .o~ Tonk.in neah ptak -LntenhiZy, 8 JuZy1973, 0432 GMT. (OMSP imageky)

21

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22

BILLIE

Billie, the season’s first super ty-phoon, became a tropical depression in thewestern Philippine Sea some 250nm east ofLuzon on 12 July. Her early history can betraced to the Yap-Palau area on 10 July asa weak circulation in the monsoon trough.

Billie initially tracked westward,gradually shifting to the northwest in res-ponse to a long wave, mid-tropospherictrough over eastern China. Reaching tropi-cal storm force late on the 13th, Billieassumed a northerly course at a speed of 7kts.

The long wave trough remained station-ary, influencing Billie to maintain a me -ridional track at about 8 kts. Her centernever deviated more than 30nm either sideof 125.5E for 4 days, covering a distanceof 720nm. This steadiness in direction forsuch an extended period of time sets Billieapart from any other northward moving ty-phoon during the period 1947-1972.

Rapid deepening occurred once typhoonforce was attained early on the 14th asBillie’s central pressure fell 50mb in 24hours. At 15/0330 GMT, aircraft reconnais-sance indicated that the central pressurehad dropped to 916mb within a tightly or-ganized eye 8nm in diameter (Figure 4-5).

Billie’s central pressure rose to 954mbduring the next 18 hours as she approachedthe Ryukyus. Commencing an unusual seconddeepening as she crossed through the islandchain, Billie’s central pressure dropped to917mb in the East China Sea (16/1154 GMT).

Billie passed just east of Miyako Jima,where maximum sustained winds of 65 ktswith gusts to 104 kts were recorded (16/

0700 GMT). The lowest pressure reading atthe Japanese Meteorological Agency Stationwas 947.5mb (16/06S0 GMT).

The island of Okinawa experienced galeforce winds as Billie transited northwardthrough the East China Sea. Naha registeredmaximum sustained winds of 35 kts with guststo 58 kts (16/1700 GMT) while White BeachNaval Port Facility recorded 45 kts sus-tained with gusts to 5S kts (16/1900 GMT).Kadena AFB reported lesser winds of 28 kts(16/1640 GMT) with gusts of 43 kts (16/1354GMT) . Based on land radar, Billie’s eyepassed I05nm west of Okinawa at 16/1800 GMT.

On the 17th, a short wave deepened thenorthern portion of the long wave troughsituated in the Lake Baikal region of Si-beria, causing increased ridging over Man-churia and the Sea of Japan. This ridgingprevented Billie from recurving. On the18th, Billie shifted to a northwest course120nm southsouthwest of Cheju-do Island.Satellite imagery indicated drier air offthe Asian Mainland was entering Billie’scirculation at this time. She weakenedsignificantly during the 18th, dropping totropical storm strength late that day whiletracking into the Yellow Sea.

Approaching the Gulf of Chihli on the19th, Billie acquired extratropical charac-teristics and accelerated to a forwardspeed greater than 20 kts. Billie finallymoved inland near Chin-Chow China and dis-sipated on the 20th.

FIGURE 4-5. Typhoon %.i.tfie[tight) 7 houm ptiofito anunuhual becond deepening 190 nm eab.t 0{ Taiwan. TyphoonVo.t [Le4tl .Ln-theSOu.th China Sta, 16 Ju-Ly 1973, 0416 GMT.[UMSF -image~g)

23

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24

DOT

The South China Sea spawned its secondtyphoon of the 1973 season on 13 July withthe genesis of Dot. Her development wasquite similar to Anita’s. A surge in thelow level southwesterlies preceded herformation in the monsoonal trough.

Dot formed a few days after Billie.While Billie intensified rapidly in thePhilippine Sea to dominate the synopticsituation in the vicinity of both tropicalcyclones, Dot drifted slowly northwardremaining poorly organized (Figure 4-6).Billie’s strong mass divergence alofteffectively blocked Dot!s outflow to thesubtropical westerlies leaving a goodoutflow channel only in the southwestsemicircle. This may have been a criticalfactor in explaining Dot’s slow rate ofintensification during the first threedays of her existence.

Late on the 15th? Dot began to increaseher rate of intensification. The UnitedKingdom ship HYRIA, located 60 nauticalmiles southeast of Dot’s center, observed55 knots of wind and a pressure of 989.3mb(15/0600 GMT). She reached typhoonstrength late that evening as she acceler-ated to a speed of 9 knots towards HongKong. During this period, the separationbetween Dot and Billie began to increaseand Billie had reached peak intensity andwas starting to weaken. This apparentlyallowed Dot to intensify at a faster rate.

Besides intensity interaction betweenDot and Billie, both storms also experi-enced the Fujiwhara interaction (Figure4-7). By subtracting the steering flowfrom the resultant movement of both stormsthe interaction is quite pronounced (Brand,1968). Throughout the period of the inter-action Billie remained the stronger of the

FIGURE 4-6. Do-t ab a -ttop.icaL depxeb~,ton in .thaSouth China Sea, 14 Ju.ty1973, 0446 GMT. IDMSP imagezg)

25

FIGURE 4-8. Dot ($a~-t)oveaLand 70 nm nomtheaAt 06 Hong Kong and TyphoonB.iLLie (tight) in the Ea~.tChina Sea, 17 Jutcj 1973, 0402 GMT. (DMSPLmageky]

two . As a result, Dot’s resultant move- 38 others. Two freighters were beachement was affected much more significantly. and six others dragged anchor.Both storms rotated 124 degrees aroundthe common center of rotation.

Dot reached her peak intensity of 85knots on the 16th, about 80nm south ofHong Kong. She passed within 12 miles ofthe Royal Observatory in Hong Kong whichexperienced maximum sustained winds of 32knots with a peak gust of 76 knots. Tate’sCairn in the Colony reported the strongestsustained winds of 57 knots with peakgusts of 97 knots.

Dot weakened considerably upon makinglandfall on the northeastern side of MirsBay (Figure 4-8). She tracked toward theeastnortheast over eastern Kwangtungduring the night of the 17th as a lowpressure area and entered the East ChinaSea near Foochow as a tropical depressionon the morning of the 18th. AS Dotapproached within 120nm northnorthwest ofOkinawa, she took an abrupt change ofcourse due north in response to a buildingridge to the east and accelerated rapidly,following in the wake of Billie. Dotdissipated over the Yellow Sea on the 20th.

Damage reports from Hong Kong indi-cated many low-lying areas in the NewTerritories were flooded. Hong Kongexperienced heavy losses to garden crops,fruit trees, livestock, and farm houses.A landslide killed one person and injured

27

115” 120° 125° 130” ?35”

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28

ELLEN

The first indication of what was to be-come Ellen appeared in the surface data on15 July as an increased troughing in theextensive convergence zone southeast ofTyphoon Billie. By 17 July, high resolu-tion DMSP satellite imagery confirmed theexistence of a closed circulation in thetrough near 20°N 138”E (Figure 4-9).

Ellen evolved unusually far north inthe trailing convergence area of TyphoonBillie. Furthermore, in the early stagesof development, the upper troposphericoutflow was most obviously influenced bythe TUTT. Post-analysis of 200mb synopticcharts and satellite data indicates thatthe formation was assisted by a small, butpronounced, ridging induced on the eastside of a westward moving cell in the uppertropospheric trough.

Ellen intensified rapidly, reachingtyphoon strength by the 18th. Iwo Jima(Japanese Maritime Self Defense Force)reported southeasterlies with maximum gustof 44 knots as she passed to the west with-in 165nm (19/0200 GMT). Ellen achievedpeak intensity as a reconnaissance aircraftobserved maximum winds of 105 knots and acentral pressure of 941mb (19/0420 GMT).

During the early portion of her life,Ellen tracked almost due north as Billiehad done. She moved to the north beneath:::~gltropospheric northerly flow (35-4o

By late on the 19th, the strongvertical shearing environment caused her todeteriorate rapidly over open water (Figure

FIGURE 4-9. FoamatLve h.tagu 06 EUencenfehed 300 nm bou.thwcd~ ad lUJO Jima,77 Ju.Lg 1973, 0221 GMT. [UM-SPimagezg)

4-lo). By the 20th, the upper level anti-cyclone over Ellen had sheared off exposingher low level circulation. Convective ac-tivity at this time was confined to conver-gence areas well south and southeast of thecenter .

As a weak low-level circulation, theremains of Ellen drifted westward under theinfluence of the troughing left by Billieand Dot and a quasi-stationary anticycloneover the Sea of Japan. Satellite imageryon 23 July indicated a rejuvenation of con-vection over the circulation which thenpersisted through 28 July with varying de-grees of intensity. Reconnaissance air-craft on 24 July confirmed the presence ofa warm core, closed circulation. As a re-sult of the weak steering flow’,Ellen’smovement was erratic during the period fromthe 21st to the 28th.

On the 28th, she reintensified oncemore 9Clnmfrom the south coast of Honshu.The Japanese weather ship OJIKA and twoother ships reported winds of 30 to 35knots around Ellen (28/00002). She reacheda peak of 45 knots as a shortwave troughover the Sea of Japan caused her to moveon a northward course over south centralJapan dissipating over land on the 29th.

FIGURE 4-10. Tgphoon El-ten (hZghZ] at pea.tnXenh.i-tq.Vo.t (Led-t]ab a ~hOpiCU~dcphebb.ion, 19 Ju.tg 1973, 0333 Gh4T. (VMSPimagchg)

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GEORGIA

During early August, the tropicaluPPer tropospheric trough (TUTT) remainedto the north of and in close proximity tothe monsoon trough in the South China Sea.As a result, Georgia’s formation and sub-sequent development cannot be easilyattributed to the monsoon trough or theTUTT independently, but more as an inter-action between the two. Sadler (1973)suggests that westward moving cells in theTUTT provide an upper level westerly out-flow channel which enhances development ofdisturbances in the monsoon trough. Thistype of influence was apparent during thedevelopment of Georgia.

Georgia reached minimum tropical stormintensity on 9 August as she transited ona westsouthwest course across the SouthChina Sea at a moderate speed. She passedwithin 170nm of Hong Kong late on the 9th.Maximum sustained winds experienced atHong Kong were 41 knots with a peak gust of

73 knots. Georgia reached typhoon inten-sity on 10 August (Figure 4-11).

Maintaining her westerly track at 8knots until early on the llth, Georgia thenturned north in response to a weakness inthe high cell over eastern China. She madelandfall north of Hainan Island on 12August and dissipated over China. Georgiawas the third tropical cyclone originatingin the South China Sea to reach typhoonintensity in 1973.

FIGURE 4-11. Typhoon Geofigiain .thcSouth China Sea 140 nm eti.t06 UtinanI~land, 10 AuguhX 1973, 0500 GMT. (UM-SPAnagtzg]

31

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On the 8th of August, the monsoontrough extended 1500 nautical miles south-east-from the Luzon Strait to a positionjust west of Truk with a weak surface cy-clonic circulation imbedded in the trough420 nautical miles north of Yap. Only 24hours previously, its eastward extent hadbeen restricted to the northern part of theSouth China Sea.

During the next tw-o days, the distur-

bance drifted northwestward with littledevelopment, By the 10th, the disturlrancehad intensified to Tropical Storm Iris.She continued to move northward at 8 knots.

On the morning of the llth, the complexupper air and weak steering flow patternsresultlng from the presence of the subtrop-ical ridge to the north and the near equa-torial ridge to the south of Iris forcedher to remain essentially quasi-s;:;i;;:~yfor the next 48 hours. However,tinued to intensify during this period andby early on the 12th, developed typhoonstrength winds.

Early on the 13th, Iris began to movetoward the northeast under the influence ofthe near equatorial ridge reaching hermaximum intensity of 8S knots that after-noon (Figure 4-12).

As Hope dissipated to the east, thesubtropical ridge returned to its climato-logical position and the near equatorialridge weakened. This forced Iris to alterher course to the northwest on the 14th in

IRIS

response to the change in the steeringflow , The Japanese meteorological stationat Minami Daito Jima measured a minimumpressure of 974.7mb during the passage ofIris (14/0707 GMT), Approximately 11 1/2hours (1830 GMT] after passage of the sur-face center, the station reported peakgusts of 63 knots out of the southwest.She gradually weakened to minimum typhoonintensity prior to crossing the island ofAmami O-Shims. Two fishing vessels werereported lost in the vicinity of the islandduring her passage.

After crossing the island she reinten-sified briefly to 75 knots. By the 16th,Iris weakened to tropical storm force andtook a more northerly course (Figure 4-13).

On the morning of the 17th, Iris beganrecurving. Kunsan Air Base in the Republicof Korea experienced maximum sustainedwinds of 46 knots with a peak gust of 64knots as Iris passed within 2Snm (17/0646GMT) . She made landfall near Kaesong,Korea about 17/0800 GMT with maximum windsof 35 knots. Iris continued across Korea,entering the Sea of Japan near Wonsan wherethe maximum winds were still 30 knots. Shebecame extrotropical over the Sea of Japanas she merged with a front moving offManchuria.

Initial reports from Korea indicatedtwo persons were killed, three missing andhundreds were left homeless. A bargecarrying six persons sank in the sea offKijang - Myon, Yangsangun; 3 were rescued.

FIGURE 4-12. Typhoon ~tib [.te{t] ncah FIGURE 4-13. Typhoon ll~b 165 nm ~outhpeak .in-tenb.ity285 nm aou.thea~.t o{ Olz.i-nawa. RtmnanZ4 o{ Hope {fiigh~]ju~-t odd

o~ Cheju Do, 16 dugubt 7973, 0332 GMT.

.tht coah-to~ ifonhhu, 13 Augu~% 1973,[uMsP .imageq]

0234 GMT. IOMSP imagezg)

33

LOUISE

Louise began as a low level circulationin the monsoon trough first noted on 30

August in the Philippine Sea to the east of

Catanduanes Island. An organized cloudpattern became apparent the next day butthe surface circulation remained weak. Theweak surface low drifted towards the north-west for the next 72 hours.

By 3 September, an aircraft investiga-tive mission reported a narrow band of 6Sto 75 knot surface winds north of the lowcenter although the minimum sea level pres-sure was only 998mb (03/03S0 GMT). A 60knot wind report from the United Kingdomship SHEAF TYNE 30nm to the north of Louiseconfirmed the aircraft observation. Satel-lite imagery at approximately the same timeshowed Louise to be poorly organized. Thenear-typhoon force winds appear to havebeen a transitory phenomenon induced by thechanneling effect of the Luzon Strait. Bythe evening of the 3rd, a reconnaissance

aircraft reported maximum winds of only 40knots as Louise entered the South China Sea.

On the 4th, Louise had become a betterorganized tropical storm well on her way tobecoming a typhoon (Figure 4-14). The mid-tropospheric ridge to the north of Louisekept her on a westerly course at 10 ktsacross the South China Sea.

She passed 150nm to the south of HongKong late on the Sth just as she reachedpeak intensity of 75 kts. Throughout herlife, Louise remained a relatively smalltyphoon. Louise crossed the Luichow Penin-sula during the night of the 6th. Eighteenhours later she made landfall and dissi-pated rapidly over North Vietnam.

FIGURE 4-14. TILop.icaL S-tohm Lou.de 105 nm noh.thweh.t o~ Luzon, 4 Septembca 1973,0401 GMT. [UMSP -imagzzg)

3s

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36

MARGE

Marge entered the South China Sea onIZ September as a tropical depression, af-

ter crossing northern Luzon (Figure 4-1S).

She quickly developed to tropical stormstrength 12S nm northwest of Cape Bolinao.The early stages of Marge can be traced toa weak circulation in the monsoon troughappearing on the synoptic surface analyats750 miles eastsoutheast of :.lzon (08/0000GMT). This system tracked xest~\.ardduringthe next four days as it accelerated to aspeed of 11 to 12 knots before making land-fall on northern Luzon.

A narrow, mid-tropospheric, subtropicalridge was positioned over southern Chinaas 14arge emerged into the South China Sea.Little change in intensity or orientationof the ridge occurred during the next fewdays, dictating a westerly course whicheventually caused Marge to strike NorthVietnam 2 1/2 days later.

Maintaining a forward speed of 11knots, Marge intensified steadily afterentering the open waters of the South Chi-na Sea, reaching typhoon force as she

passed 200 nm south of Hong Kong on themorning of the 13th (Figure 4-16). Theminimum measured centraI pressure by air-craft reconnaissance, prior to the typhooncrossing the no-fly line, was 964 mb earlyin the evening of 13 September.

Striking central Hainan Island earlyon the morning of the 14th h’ith sustainedwinds estimated near 80 knots, Margeemerged into the Gulf of Tonkin ~;ith trop-ical storm force some 12 hours later.Eventual landfall was made 60 nm north ofVinh, North Vietnam durin~ the early morn-ing hours of the 15th. Subsequently,Marge dissipated rapidly inland over thehighlands of Laos.

One interesting feature of Marge duringher transit of the South China Sea was hersmall size. Similar to Louise, as a ty-phoon, her circulation did not appear toexceed 1.50miles in diameter as evidencedby ship and aircraft reconnaissance data.Typhoon strength winds were probably con-fined to the wall cloud region.

FIGURE 4-16. Tfiop.icaLS.team Mazge neaatyphoon ~.tzength 225 nm ~ou.th 06 HongKong, 13 .$ep-tembeh1973, 0106 GMT.[DM.SP -&zgezq)

37

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38

NORA

A weak surface low formed in the non-soon trough, 120 miles south of Yap, on 30September, and drifted northwest for thenext two days. By the evening of 2 Otto.her, the tropical disturbance had intensi-fied to Tropical Storm Nora. Reconnais-sance aircraft reported maximum flightlevel winds of 45 kts and a minimum sealevel pressure of 987 mb.

Nora continued a gradual intensifica-tion until early on the afternoon of the5th when her winds exceeded 100 kts.During the next 20 hours, as she movedwestward at 9 kts toward the Republic ofthe Philippines, Nora’s central pressureplummeted 66mb to 877mb with maximum sur-face winds of 160 kts (Figure 4-17). Her

central pressure ranked among the lowest onrecord (Jordon, 1961).

On the evening of the 6th, the high re-solution DMSP infrared imagery revealed thetypical anticyclonic outflow pattern in thecirrus . The infrared data was then “thresh-holded” to display only the colder portionof the infrared spectrum sensed by the ra-diometer (Figure 4-18). It revealed whatappeared to be a tightly wound band spi-raling out from the eye wall. Nora was asuper typhoon at this time with estimatedmaximum winds of 140 kts.

When Nora was 225 miles east of Manilaon the morning of the 6th, she took a morenorthwesterly track in response to an

FIGURE 4-17. SupefiTyphoon Noaa (Ledt] at peak .Ln-tenh.i.tq200 nm eab.tnohXheah.to{ Catanduancn IbLand. Fotma.tkveh.tagti06 Patiy (1-igh.t) with low Levelcihcu~ation cen.ttfi expobed, 5 Oc.tobea 1973, 2312 GMT. [OMSP -imagefig]

39

?5

Iii

FIGURE 4-18. T/zmc~ho2ded .in~kated imagefiy 06 Noaa d.dplaying onlg -thecotdez pofik.iono~ -the in~hantd hpt?c.txumhenhed bg the kad.iome.tth,6 Octoba 1973, 1753 GMT. (OMSP imagfvuf]

approaching shortwave trough over China. damage to crops, public and private properNora skirted the northeast tip of Luzon ty were reported. A Philippine freighterwith maximum sustained winds of 100 kts and ASIAN MARINER was reported sunk by Typhoonweakening. Nora in the Taiwan Straits. All 38 crew

members were rescued. The Greek freighterAs she transited the Luzon Strait on BALTIC KLIF was also capsized and sunk by

the 8th a dramatic rescue operation was oc- Nora some 80nm southwest of the Pescadores.curring in the Taiwan Strait. In thirty Three of the crew were drowned with severalfoot seas and 50 kt winds, the Missile Frig- missing and presumed lost. Taiwan alsoate USS WORDEN rescued seven fishermen a- suffered extensive damage from Nora.board the Taiwanese fishing vessel JAI TAI Twelve persons were reported dead and 28NR3 from the approaching typhoon. One unaccounted for. Nearly 8,000 people wereTaiwanese crewman was lost at sea. The left homeless with Nora destroying over afishing vessel had been floundering in thousand houses and damaging hundreds ofheavy seas with the forward section split others.lengthwise (Figure 4-19).

Nora passed within 60nm of Kaohsiung,Taiwan as she accelerated to a speed of 12kts toward the northwest. She made land-fall near Amoy in southern China on themorning of the 10th and degenerated into alow pressure area.

Luzon in the Republic of the Philip-pines suffered considerable damage. It wasreported that 6 persons were killed and O-ver a hundred thousand people were lefthomeless. Estimates of over $2 million in

40

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OPAL

inofon

Opal formed in an active monsoon troughthe South China Sea. The first evidencea weak surface low appeared in the troughthe 1st of October. However. it wasn’t

until late on the 3rd that significantcloudiness associated with the incipientstorm became apparent.

Early on 4 October, Opal reached minimaltropical storm intensity about 75 nm north-west of Nanshan Island. She moved to thenorthwest at 6 to 7 knots in response tothe high pressure cell over eastern China.By the 5th, she had developed typhoonstrength winds (Figure 4-20).

On the morning of the 6th, Opal abrupt-ly changed her course and moved northeast-ward. She remained on this course for thenext 12 hours before resuming a westnorth-Westerly hedi,ng. A reasonable explanationfor the temporary eastward movement may

rest in a Fujiwhara interaction with typhoonNora. Nora was positioned in the PhilippineSea about 750 nautical miles from Opal and

reached maximum intensity almost coinciden-tly with the eastward shift in Opal. Also,Nora turned to a more northerly track atthis time. Brand (1968) reports a maximumdistance for interaction of about 7S0 nau-tical miles. He demonstrates that the angu-larchange rate of a line connecting thestorms at this distance should be verysmall, only 3 degrees per 12 hours. Theactual change was somewhat smaller, indi-cating the weakness of the interaction. Theshort period of the interaction may be dueto the terrain effects of the interveningRepublic of the Philippines, among otherfactors, as Brand suggests that the binaryrotation is due to the circulation of theinflow layer which occupies only the lowestfew thousand feet.

Maximum winds of 70 to 75 knots wereobserved during the 6th and early on the7th as Opal resumed her westnorthwest move-ment. Opal moved ashore north of Qui Nhon,Republic of Vietnam late on 7 October andrapidly dissipated.

FIGURE 4-20. Thopica.t S-tohmOpa.t in the Sou-th China .SIZa 225 nm~oufhaab.t od Qui Nhon, 5 Oc.tobtt 1973, 045g GMT. (OMSP .imagefiy)

43

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PATSY

A weak disturbance formed in the mon-soon trough 300nm south of Guam on the 3rdof October. The weak vortex drifted west-ward in the wake of Nora. Until the 6th,it underwent only minor development due tothe strong vertical shear caused by Nora’svigQrous upper tropospheric outflow. Re-connaissance aircraft, investigating thedisturbance on that day, reported maximumsurface winds of 35 kts, heralding the ar-rival of Tropical Storm Patsy.

For the next two days she followed awestnorthwest course at 6-8 kts under theinfluence of the steering flow of the mid-tropospheric ridge to the north. Patsy wascharacteristically a small storm throughouther life. By the 8th she had developedtyphoon force winds as she began to accel-erate to a speed of 10-12 kts.

A reconnaissance aircraft reported thatPatsy had rapidly intensified into a supertyphoon with estimated maximum surface windsof.150 kts and a central pressure of 893mb(10/0020 GMT). Her central pressure haddropped 57mb in a span of 22 hours (Figure4-21).

Patsy continued unerringly toward thenorthern tip of Luzon as she began toweaken late on the 10th. Interestingly, on

FIGURE 4-21. SUPIZR Typhoon pcltby[z-igh.t)a-t peak .in-teti-i-tq.TyphoonNoka [.ta~t]in -theTaiwan S.tfia.it,9Oc-tobet 1973, 2341 GMT. (UMSP -Lmagucyl

the evening of the llth, DMSP satelliteimagery revealed that Patsyfs low levelcirculation had separated from the upperlevel portion of the cyclone (Figure 4-22).The low level portion took a more northwest-erly course and weakened to a tropical dis-turbance as it crossed the southern LuzonStrait. Meanwhile, a radar site in theRepublic of the Philippines continued tofollow the upper level cloudiness as ittracked due west towards Luzon. A similarsituation occured with Susan in 1972.

The upper level circulation drifted overLuzon and out into the South China Sea. Itapparently became superimposed over a low

level vortex that had been situated in theSouth China Sea for several days. Thissystem developed to tropical storm intensityas it passed to the north of the ParacelIslands. It weakened to a tropical depres-sion just prior to making landfall in theRepublic of Vietnam.

Patsy was the 3rd and final super ty-phoon of the year. She was only the 2ndstorm to form in the western Caroline Is-lands area in the 1973 season.

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RUTH

The formative stage of Ruth appegredearly on 10 October as a weak circulationin the monsoon trough in the western Caro-line Islands. By the llth, an area of en-hanced convective activity associated withthe cyclonic circulation became evidentfrom satellite imagery. Ship reports on’the afternoon of the llth located TropicalStorm Ruth about 250nm westsouthwest ofGuam with maximum winds of 35 kts.

Ruth followed 3 days behind Patsy. Shetracked approximately 120nm to the south ofbut parallel to Patsy’s track across thePhilippine Sea. It is interesting to notethat although Patsy intensified rapidly tosuper typhoon strength, Rut<hdevelopedslowly and reached typhoon intensity threedays after she became a tropical storm.(Figure 4-23). The satellite data for thisperiod showed little or no convective acti-vity on the north side of Ruth. The stronguPPer tropospheric northeast flow from thesubtropical ridge may have contributed tosuppressing the outflow from Ruth on thenorth side and thereby inhibiting herdevelopment.

She continued her westerly movementwith slow intensification until landfall onLuzon on the 15th, with maximum sustainedwind speeds of 85 kts. Rapid weakeningthen occurred as the low level inflow wasdisrupted by terrain effects. Her maximumsustained wind had decreased to 50 kts bythe time she reached central Luzon.

Ruth passed 42 miles north of ClarkAB late on the night of the 15th where

FIGURE 4-23. Taopica& S.tofim Ruth hthe Ph.i.Uppine Sea 225 nm eab$ 06Catanduanu IbLand, 14 Oc.tobti 1973,0009 GMT. (OMSP .imagefiq]

maximum sustained winds of 30 kts and peakgusts of 43 kts were recorded. Only minordamage was reported at Clark AB. Balerrecorded maximum peak gust of 95 kts fromthe north (15/1355 GMT) while Casiguran 50nm further north on the coast experienced agust to 98 kts three hours later (15/1700GMT) .

On the 16th Ruth entered the SouthChina Sea and tracked westward toward theParacel Islands, still under the steeringinfluence of the subtropical ridge (Figure4-24). A Japanese ship IDEMITSU MARU re-ported 50 kts of wind and a surface pres-sure of 995mb as she passed 90nm northwestof Ruth (16/0000 GMT). She reintensifiedon her sojourn across the South China Seareaching a maximum intensity of 90 kts onthe afternoon of the 17th just east of theParacels. Shortly after attaining her max-imum intensity, Ruth turned to a northwest-erly course in response to a weakness inthe subtropical ridge. She then crossedHainan Island and entered the Tonkin Gulfwith maximum sustained winds of 50 kts.Ruth continued to weaken rapidly as uppertropospheric support waned, and dissipatedcompletely as she moved inland along theNorth Vietnam coast on the afternoon of the19th .

Damage reports indicate that while Ruthwas crossing Luzon, 27 people were killed,30 people were injured and 23 people weremissing. Property damage amounted to morethan five million dollars (U.S.) with thou-sands of homes destroyed.

FIGURE 4-24. TtiopLcaL .Wohm Ruthfcehtcnhidy,hg a{-ten e~ohh.ing Luzon,16 Oc20bc~ 1973, 0359 GMT. [UMSPimagezg)

47

3. TROPICAL CYCLONE CENTER FIX DATA

a. DISCUSSION OF DATA:

Fix data from all sources are in-cluded for each tropical cyclone. Thefirst four columns of the mint-out listthe same information

FIX NO.-

TIME -

POSIT -

FIX CAT-

regar~less of platform.

Fixes are numberedsequentially.GMT time in day, hour,and minutes of fix.Position of the stormin degrees and tenths.Fix platform used(SAT-- satellite, P -penetration, LRDR -land radar, AC R -aircraft radar, SRDR -ship radar, CPA - sta-tion experiencing cen-ter passage, SCF -

synoptic chart fix).

The format of the remainder of theprint-out varies with the platform.

(1) SATELLITE - These data were de-rived from bulletins received from

FLEWEAFAC.and NESS Suitland, Maryland (NOW-

Z), the APT site at U-Tapao, Thailand (ESSA-8), or DMSP (formerly DAPP) data from vari-ous sites (Chapter II). Intensity esti-mates (when available) are listed using theNESS classification system (NOAA TechnicalMemorandum NESS 45). If the source wereDMSP (DAPP) data, the PCN (Position CodeNumber] appears followed by the name DMSP.If the platform were NOAA-Z or ESSA-8, thatname will appear after the intensity infor-mation along with the site name and loca-tion confidence number (NOAA-2 only), (NHOP,1973) . NOAA-2 fixes without a site namewill be assumed to be FLEWEAFAC Suitlandfixes.

(2) RADAR - The latitude and longi-tude of land-based radars are given in thePOSIT OF RADAR column. The position of mo-bile radar platforms are included if availa-

ble. Plain language remarks appear afterAC~W radar reports regarding tropical cy-clone characteristics, size, and accuracyof fix (CINCPACINST 3140.lL, 1973). Al1other land radar reports contain a 5-digitcode group identical to the WMO radar codefor reporting tropical cyclone characteris-tics as regards to size, development, andaccuracy of location of the center or theeye. A list of land-based radars providingdata in the fix print-out is given in Table4-7.

(3) CPA - If a station experiencescenter passage, maximum surface wind ob-served and minimum sea level pressure re-corded are listed.

(4) SCF - If synoptic data is denseand consistent enough to provide accuratefix information, the derived storm positionis listed. Maximum surface wind and mini-mum sea level pressure values are included,if possible.

(5) AIRCRAFT PENETRATION - Thesedata were normally obtained at scheduledfix times. Additional reconnaissance air-craft fixes are made during the peripheral

data gathering legs between scheduledfixes. These fixes normaIIy provide date,time, and position data only.

The categories containing informationfrom reconnaissance aircraft fixes aTe:

(a) ACCRY (Accuracy)

The estimated navigation(first number) and meteorological (secondnumber) accuracies are expressed in nauti-cal miles.

(b) FIX LVL (Fix Level)

A constant-pressure-surfaceflight level (listed in millibars) is nor-mally maintained during a tropical cyclonefix mission. Low-level missions (1S00 feet)aTe conducted at a constant, true altitude.

(c) MAX OBS FLT LVL WND

Wind speed (kt) at flightlevel is measured by the AIJ/APN-82 doppleTradar system aboard the WC-130 aircraft.The values entered in this category repre-sent the maximum wind measured prior to ob-taining a scheduled fix. This measurementmay not represent the maximum wind becausethe aircraft samples only those portions ofthe central core region along the flightpath. For this Teason, the maximum observedmay be significantly lower than the truemaximum wind in the circulation (i.e., pene-tration through weak semicircle on firstfix) .

A limitation of the dopplerradar system occasionally prevents themeasurement of the maximum wind in intensetyphoons. In areas of heavy rainfall, theradar may track energy reflected from pre-cipitation rather than the sea surface, pre-venting accurate wind measurement. Also ,the doppler radar mount on the WC-130 re-stricts wind measurements to drift angles<27° if wind is normal to heading of air-~raft.

(d) MAX OBS SFC WND

The maximum surface wind(kt) observed from flight level is enteredin this column. The observation is an es-timate based on the state of the sea (referto 9WRWGM 105-1, Vol II, pp 2-27-28). Thesampling limitation noted in paragraph (c)also exists for this category. In addition,availability of these data is dependent onthe absence of undercast conditions. Theposition relative to the vortex center ofitems (c) and (d) need not coincide.

(e) OBSMIN SLP

The minimum observed sealevel pressure is normally obtained from adropsonde released in the vortex center.If the ocean surface is visible, the drop-sonde will be released over the center ofthe area of calm seas; otherwise it is re-leased at the flight level wind center. Ifthe fix is made at 1500 feet, the sea levelpressure is extrapolated from that level.

●

48

(f) MIN 700 MB HT

The minimum height of the 700mbsurface in the vortex center is recordedin decimeters.

(g) FLT LVL T;/Tn

This denotes maximum temperaturemeasured in the center (Ti) and ambienttemperature outside the center (To). Am-bient temperature is measured just priorto entering the wall cloud. Both tempera-ture observations are in degrees celsiusand are made at a flight level of constantpressure surface (7oo, SOO-mb).

Reconnaissance aircraft seldompenetrate on the same azimuth from one fixto another. Thus ,

‘he position ‘f ‘i?innormally varies from the center, botbearing and range. The distance is direct-ly dependent on radar definition of thestorm.

REFERENCES:

Brand, S., “Interaction of Binary TropicalCyclones of the Western North PacificOcean,” NAWEARSCHFAC Tech. Paper No.26-68, September 1968.

CINCPACINST 3140.lL, “Tropical CycloneOperations Manual,” June 1973.

FLEWEACEN/JTWC, Annual Typhoon Report,Guam, Marianas Islands, 1970.

Ramage, C.S., Monsoon Meteorology , AcademicPress, New York and Londcn, 1971, pp.189-190.

Sadler, J.C., l~TheRole of the Upper Tro-pospheric Trough (TUTT) in Early SeasonDevelopment,” ENVPREDRSCHFAC Tech.Paper, 1973 (in press).

U.S. Dept. of Commerce, NOAA, FederalCoordinator for Meteorological Servicesand Surmortin~ Research. “National

(h) EYE FORM/ORIENTATION/DIA Hurric~ne Ope~ations Pl~n,” May 1973.

The shape and diameter (nauticalmiles) of the eye are determined by radar.This is reported only if the center is SO%or more surrounded by wall cloud (seedefinition in Appendix). The orientationof the major axis is for elliptical cases.Abbreviations for the eye form are:

CIRC - CircularELIP - EllipticalCONC - Concentric

TABLE 4-7. LAND RADAR SITES

Location StatioriNo. ICAO Station Name

10.3N 124.OE 98646 RPMT Mactan98440

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68

CHAPTER V — SUMMARY OF FORECAST VERIFICATION DATA

1. COMPARISON OF OBJECTIVE TECHNIQUES

a. GENERAL :

Objective techniques have beenverified yearly since 1967. Year-to-yearmodifications and improvements have pre-vented any long period comparisons of thevarious objective techniques except forEXTRAPOLATION and ARAKAWA (1963). All ofthe dynamic objective forecast techniquesused during the past season employed thesimple steering concept of a point vortexin a smoothed flow field with adjustmentsbased on past movement. None of the tech-niques provided intensity forecasts withtheir associated relationship to movement.

b. DISCUSSION OF OBJECTIVE TECHNIQUES:

(1) EXTRAPOLATION - Past 12-hourmovement derived from current warningposition and 12-hour old best track posi-tion is linearly extrapolated to 24 and 48hours.

(2) ARAKAWA (1963) - Grid overlayvalues of surface pressure are entered intoregression equations. Previously hand com-puted, computations were computerizedduring the latter half of the 1972 season.

(3) MOHATT 850/700 - A modificationto the basic HATRACK program which advectsa point vortex on a pre-selected analysisor prognostic SR (space mean) field atdesignated levels in six-hour time stepsout through 84 hours. Utilizing the 12-hour history position, MOHATT computes theprevious 12-hour forecast error and appliesa bias correction to the forecasted posi-tions out to 72 hours.

(4) TYMOD 12/24 - A modificationto FLEWEACEN Pearl Harbor’s objective tech-nique TSGLOB. TYMOD advects a weighted,point source using FNWC Monterey’s globalband upper air progs out to 72 hours. out -puts are provided for both 12- and 24-hourhistory.. Bias corrections are applied tothe forecast positions based on the pre-vious 12- and 24-hour forecast errors.

(5) TYFOON-72 - Modified version(Jarrell and Wagoner, 1973) of the basicTYFOON program (Jarrell and Somervell,1970). The program outputs forecast posi-tions as the centers of probability ellip-ses out to 72 hours based on a group ofanalog storms which occurred within a time/

mMONTHLY DISTRIBUTION

JFMAMJJ ASOND00001166 S430

space envelope centered about the date andposition of the storm being forecast. El-lipses are based on the analog populationweighted according to their similarity tothe existing storms.

c. TESTING AND RESULTS:

In past years only one or two ob-jective techniques provided 72-hour fore-casts. For the first time, during 1973,the JTWC had five objective techniques toassist in formulating the 72-hour outlook.Although some of the objective techniquesshowed certain skill at various time frames,research is continuing in an effort to im-prove all of the objective techniques usedby the JTWC.

(1) Table 5-1 presents a comparisonof all objective techniques for all fore-casts. Each objective technique is com-pared to the best track, each of the otherobjective techniques, and the official JTWCforecast. A comparison of the varioustechniques shows EXTRAPOLATION to be super-ior to all other techniques at both 24 and48 hours. When compared to the officialJTWC forecast, EXTRAPOLP.TION was onlyslightly higher at 24 hours and equal at 48hours. TYFOON-72 was the second best tech-nique at 24 and 48 hours and superior tothe other techniques at 72 hours. When com-pared to the official JTWC forecast at 72hours, TYFOON-72 was only slightly higher.

(2) Table 5-2 presents a comparisonof all objective techniques for all ty-phoons where the maximum sustained surfacewind was 35 knots or greater. Once again,EXTRAPOLATION was superior to all othertechniques at both 24 and 48 hours andTYFOON-72 was best at 72 hoqrs. When com-pared to the official JTWC forecast, how-ever, EXTRAPOLATION was equal at 24 hoursand slightly better at 48 hours. This in-dicates the regular tracks most typhoonsdescribed once they became well developedplus the lack of major recurvers duringthe 1973 season.

2. SUMMARY OF TROPICAL CYCLONEFORMATION ALERTS

For the fourth consecutive year, theJTWC issued Tropical Cyclone Formation A-lert messages as a means of alerting De-partment of Defense interests to poten-tially dangerous tropical disturbanceswhich normally had not reached the tropicaldepression stage.

Of the 26 tropical disturbances in thewestern North Pacific during 1973 for whichalerts were issued, 22 were placed in warn-ing status. Only Tropical Storm Hope,which developed from an upper troposphericlow, was not preceeded by a formation a-lert. Including revisions extensj.ens, andregenerations a total of 43 formation a-lert messages were issued.

The high ratio of tropical cyclones toformation alerts, 85%, can be attributedto the improved satellite interpretationprocedures employed by the JTWC. Of the

69

43 alerts issued, 30 were based solely onsatellite data, three on aircraft investi-gative, and two on synoptic data. Theremaining eight alerts were based on a com-bination of satellite plus aircraft, synop-tic data, or land radar. Thus , 88% of allalerts issued during 1973 employed satel-lite data as their basis.

3. ANNUAL FORECAST VERIFICATION

Forecast positions for the warning, 24-,48-, and 72-hour forecasts are verifiedagainst the best track using two criteria:

a. Only those forecasts for tropi-cal cyclones which reach typhoon intensityand the best track winds are 35 kts orgreater are verified; and

b. All forecasts for which besttrack positions exist are verified.

No verification statistics are computedfor the 12-hour forecast positions. How -ever, the lZ-hour forecast position errorsmay be estimated by adding half the differ-ence between the warning and 24-hour fore-cast position errors to the warning posi-tion error.

In addition to the methods described a-above for verifying absolute error distance,a computation of closest distance to thebest track (right angle error) is also cal-culated for both methods. This is used tomeasure the demonstrated ability of theJTWC to forecast the path of motion withoutregard to speed.

Unless otherwise indicated, the follow-ing tables and figures depict the distribu-tion of the typhoon criteria forecastingerrors in the JTWC forecasts.

TABLE 5-1. JTWC ANNUAL AVERAGE FORECASTERROR

24-HR 48-HR 72-HR— —

1950-58 170 --- ---1959 *117 *267 ---1960 177 354 ---1961 136 274 ---1962 144 287 4761963 127 246 3741964 133 284 4291965 151 303 4181966 136 280 4321967 125 276 4141968 105 229 3371969 111 237 3491970 98 181 2721971 203 3081972 1?: 245 3821973 102 193 245

‘Forecast positions north of 35°N were notverified

4. REFERENCES

Arakawa, H., “Statistical Method to Fore-cast the Movement and the Central Pres-sure of Typhoons in the Western NorthPacific,” Japan Meteorological Agency,Meteorological Research Institute FinalReport, October 1963.

Jarrell, J.D., and W.L. Somervell, Jr., “AComputer Technique for Using TyphoonAnalogs as a Forecast Aid,”NAVWEARSCHFAC Tech. Paper No. 6-70,June .

Jarrell, J.D., and R.A. Wagoner, “The 1972Typhoon Analog Program (TYFOON-72),”ENVPREDRSCHFAC Tech. Paper No. 1-73,January 1973.

D

70

kABLE 5-2. 1973 OBJECTIVE TECHNIQUES VERIFICATION FOR TYPHOONS ONLY (see criterion a)

24-tlOUR

UK m AB.KH S&4 Ix-32 m MtM.i B?i2.Q

JTWC 195 102102 0 1

XTRl 164 100 164 100100 0 100 0

ARXU 42 92 40 102 42 120120 28 122 21 120 0

TY24 144 98 136 97 38 124 144 216216 118 220 123 195 71 216 0

H-iNU61BER X-AXIS

TECHNIQUEC& ERROR

Y-AXIS ERRORTECHNIQUE DIFFERENCE

ERROR Y-x

TY12 150 99 140 97 38 124 142 216 1s0 181181 82 182 8s 166 42 181 -36 181 0

/

TYFN 170 99 1S4 98 41 121 143 215116 17

148 181117 19 106 -15

170 116115 -101 11s -6S 116 0

/

MH85 135 102 129 97 35 124 120 223147 44 146 49 131 8 146 -77 :5: ~:~ m ::; 14;

MJi70 125 101 119 9S 34 126125 2s

113 192 118 138 122 105 124 131 125 12S124 28 120 -6 123 -69 123 -3S 124 20 12s -6 12s o

I

JTWC XTRP——

JTWC 136 193193 0

KTRP ;;: 192 124 191-2 191 0

ARKW 33 187 31 191280 93 276 85

TY24 104 1B7 102 185389 202 395 210

AI(KW—

33 280280 0

30 283360 77

~

109 392392 0

48-HOUR

TYI 2 TYFN MS8S MH70—— ——

J’2wc - OFFICIAL JTWC SU8JECT1VE FORECASTXTRP - EXTRAPOLATIONAFtxw - ARAxAnATT24 - TTMOD WITH 24-25SHISTORYTT12 - TT260DHITN 12-HR HISTORYTfFN - TTFOON WIGNTED CL3NO)WH8S - 310HATT 8S0-MB PROGNH70 - MOHATT 700-)SSPROG

TY12 108 r86 106 183 30 283 107 393 115 360

3S2 16S 3S8 175 330 4? Y56 -37 360 0

TYFN 125 190 117 189 32 287 108 391 113 3s7 132 21S

210 20 214 2S 222 -6S 203 -189 20s -1s2 213 0

MH85 98 196 96 188 27 264 91 400 97 357 101 210 103 312

314 118 314 127 266 2 308 -92 311 -46 308 98 312 0

rci70 92 19S 91 186 27 264 87 399 92 35S 9s 209 97 311 97 291

294 99 293 107 2s1 -13 282 -117 288 -67 288 79 291 -20 291 0

72 HOURJTk’cT~~-rr ~~—

JTwc 88 24s24S O

TY24 71 2S2 76 618616 364 618 D

7Y12 73 247 76 618 80 563546 300 SS6 -62 S63 O

2TFN 82 246 7S 615 79 S66 92 291267 21 271 -344 278 -288 291 0

Mws 63 254 60 613 64 S32 6 276 69 S1352S 270 sol -112 SCM -28 S07 231 Sls 0

M170 61 2S4 38 60S 62 327 6S 277 67 494 67 499499 246 477 -128 4E9 -38 493 216 499 4 499 0

~ABLE 5-3. 1973 OBJECTIVE TECHNIQUES VERIFICATION FOR ALL FORECASTS (see criterion b)

I

24- HOUR

JTWC

JTWC 267 108108 0

XTF@ 218 104109 5

A8xW 4s 97127 30

‘2Y24 184 102208 106

TY12 192 103173 72

TYFN 21S 103120 16

FW8S 161 106148 42

XTRP ARKli TYFN MH85 ~

218 109109 0

43 110 4S 127130 20 127 0

176 105 41 132211 106 201 69

1b2 10S 41 13217s 70 175 43

198 106 44 128120 14 112 -16

f: lj; 37 130136 6

1S4 208208 0

182 208 192 17517s -34 175 0

183 207 190 174119 -89 119 -SS

143 218 :8 :;:147 -71

4NUMBER X-AXIS

TECHNIQUEC& ERROR

Y-AXIS ERRORTECHNIQUE D1FFERENCE

ERROR Y-x

Es’’”21s 120120 0

124 161 14847 148 0

MH70 149 105 143 104 36 132 134 191 141 159 146 112 ;$: 134 149 12R

128 24 127 24 124 -8 126 -65 126 -33 128 1S -6 128 0

1

I

JTwJ

JTWC 153 197197 0

XTRP 137 197197 0

ARKW 33 187280 93

TY24 116 192397 20s

TY12 120 19’23S8 166

TTFW 137 1:;209

MH8S 105 203311 108

m ~ ~

1s0 201201 0

31 191 33 280276 85 280 0

120 192 30 283 128 398402 210 360 77 398 0

12s 190 30 283 126 399361 171 330 47 3S8 -41

136 194 32 287 127 397212 18 222 -65 203 -194

107 196 27 264 101 413313 117 266 2 308 -103

JTWC -XTRP -ARKw -TY24 -TY12 -TYFN -MH85 -WH70

OFFICIAL JTWC SUS.7ECTIVEEXTRAPOLATIONARAKAWATTWOD WITH 24-HR HISTORY‘2Y?40DWITH 22-HR HISTORYTTFOON [WEIGHTED CLIMO)MOHATT 850-M2 PROGMOHATT. 700-M8 PROG

FORSCAST

1133 361361 0

133 358 152 212204 -1S4 212 0

108 367 112 213 114 311310 -37 307 9s 311 0

MH70 99 202 102 195 27 264 97 413 103 366 106 212 108 310 108 291

293 91 293 98 231 -13 283 -128 288 -78 289 76 291 -19 291 0

72 HOURJ= T= mglQ w> ~ W&l

JTWC 97 23;2S3

TY24 79 261 95 617611 3S0 617 0

TY12 81 2S6 95 617 :;; 377s50 294 570 -47 0

TYFN 90 254 94 61S 99 579 y; 319266 12 305 -S10 313 -267 0

L0485 68 264 73 625 78 S72 81 325 83 533529 265 521 -104 526 -4S S28 203 533 0

!4J70 66 264 70 617 75 S71 78 323 80 513 & S26506 242 305 -113 519 -52 522 199 526 12 0

23

72

-4t.+

WoNM

v

—-— —. ——. ——1 500

72 r II I

450 450

I

400 400I d

3501-- 350

300 =1 I I A. I ml 300I250 I 250

I200 200

~24 w

HI I I I I II I Ill 11I

150 ml

100 ~ — — — — — — — ~—I

50wI--lwl-t

‘Yr-r--rr--rr-n”250 W +.——.—

I I --—4

t200 —

48 hr e “ror

I150

250

200

150

‘:F7W+H++._._....j.-. ...-..+~~()

o L__l&.+—_L_L_.L__L_L__L__J1966 1967 1968 1969 1976 1971 1972 1973

4. SUMMARY OF INDIVIDUAL TROPICAL

STORM VERIFICATION

‘ABLE 5-4. 1973 JTWC ERROR SUMMARY

I.Averageerrorsare given in nautical miles)

WARNING 24 HOUR 48 HOUR 72 HOUR~~ ~~ERROR ERRORCYCLONE _ _WRNGS ERROR ERROR CASES ERROR ERROR CASES ERROR ERROR CASES

1. TS WILDA 12 7 63 50 ------ ------ ------2. TY ANITA 22 13 1: 1s7 104 : 240 3

TY BILLIE 20--- ------

17 24::

65 20 151 1;: 16 210 171TS CLARA 28 20 7 ;2 88

123 ------ ------ ------

TY DOT 25 15 19 123::

79 11 256 156 2 ------ ---TY ELLEN 17 13 28

7.135 16 201 116 6 55

1:;53

TS FRAN 582

27 172 --- --- ---8.

--. ... ---TY GEORGIA 17 12 1: 114 96 Ii 255 225 7 279 243 1

32 13 114 96 9 9 181 155;6. ;; !%; 24 :: 30 138 96 26 26S 1.53 2111. TD 11 15

32; ;;+ ‘;;155 2 ------ ... ..- ------

12. TS JOAN :; 43 1: 191 1:: 6 ------ ------ ------13. TS KATE 21 11414. TD 14 :: 16 : --- -:: -f ::: ::: ::: ::: ::: :::15. TY LOUISE 21 14 18 104 71 14 225 180 9 294 173 316. TY MARGE 12 67 8 224 166

:! 18 1:;3 ------ ---

17. TY NORA 77 30 192 156 24 267 21818. TY OPAL 26 12 :: 98

2062 11 177 --- ------

19. TY PATSY 14 29 65 37 22::

212 1:: 2: 318 17020. TY RUTH 12 33 84 51

1729 126 78 24 163 90 21

21. TS SARAH 13 10 4 ------ -- ------ ------ ------22. TS THELMA 35 15 10 146 35 263 283 28323. TS VI?&! 2! 1%!

139 19 28 116 78 172 ; 236 221 3

ALL FORECASTS 24 15 374 108 267 197 134 153 253 162*TYPHOONS 19 12 ;:

97239 102 195 193 131 136 245 153 88

*Includes only forecasts on cyclones that became typhoons and only when verifying best track wind was 35 kt.

NM190

170

t80

130

110

90

?0

so

1 1 I I t I t I I 1 IM3nl Ian I I

4......AW.........I I I I I IIAA llfi A -a I 64-73

AvG.........64-73

=130

10

74

&

Wzt

l;;:;;;;;

::”$”;::;

.S;II

;;:::;::::

-a=-111::::

:;$::;::

:;;;

:;;;,Aw

wll

1::::

..-”m

:!,:

0$3,

,8,z:’’”a:

::::_+

:;;;

2“”z.21111

:Islba

,llll

,.

..

..

..

..

..

.I,,

,:~:

;,,,,{/:

*.,,

,$’,

6. TYPHOON DATA

J18006 5 JUI 10 1s002 8 .JLL

~oboo~ 13 .IU1 To 18001 )9 JbL

J,$-,: m H::%::

6 -20 28.8A 176.2E 90

16 -20 JO.5tI 1>5.2E 90

zt :3 51:8K I;$:2E9!?20 -10 d2.5h 1?5. OE 70

S -10 330mk 125.5E 65

-3 . 36.3& 176.2E 55‘-10 ---- ----- --

fg :3 :::: ----- ------- .-

190000Z 35.lN 122.0S, 50 34.9N 120.8E 5LI 60 0 ---- ------ .-

TVPNOONS b’tilLE MIND OVER 35KTS

AVERkGE FORECAST ERRORUA;;~G zi-HR 48-nR 72-FIR

79NM 151Nh 21oNM

81 M Ah LF ERRoRi%~ig~ NA&~Tuo~ OF WIWO ERMOR

17NM 123N~ ]8K1S fi~S tOK. S ‘~ %S

AVE!+AGE ~I~~R~~4~J~0 ERRORNU6GIER O

-6KTS -~3&KTS -~~KIS .:jKTS2*

I6 -2o44 -153 -15

21 -10

3+ -5

015 i:

* ::

.- -.-- -.

-. -.

u29.5N 126.2E 85 12%30.e N 124.3t t15 114 &32.1 N 126. oE 80 1s6 *S

33.7N 126.7E 8Q 165 :5

~$::N 123.9C 55 1*1 S----- -- -. --

---- ----- -- -- ------ ----- -- -- --

----- ---.- -- -- ------- ----- -- -- --

:: ..- ----- -- -- --.- . . . .. -- -. ------- ----- -- -. -.

ALL FORECASISUARNING 74-HR 68-”R 72-wI

ZONM 7qNM 151hM 21ONM

llh~ 6,NM 17~NqaK s l.eKls ‘:;%s 3 K s

::KTs -j!K’s -ilKTs -::K’s

32. an la3 .eE---- --...----- --. o.-

---- --...-

--, - ---/.--, - ---------- ------.-. . ---a.-

15--..----..------..-

64 2s-- -.-- --

-- --

-- .-.- -.

-- -.-- --

---- ---------- ------ :: ‘d ::--6- ------ -- -- --

---- ------ --- -- . .

---- ------ --- -- --

77

-0600Z 14 JLN TO OboOZ 20 JIIL

4i2 HOUR FO@ECAST

!% 90s1110 ---- -----

MJIR ~QqfiD-- .-

.72 lbOUFl PCRECbS1

Rcs IT MDhu

I

8:20-- -- -.-- -- -.-- -- --

.- -. .-

.- -- .-

-- --- --.- -- --

.- -- .-

. . .. . --

.- -- ---. -- . .

. . -- --

-- .- --

.- -. --

. . - ---- -- --

.-a. --- o,-

-.. . --. .,.--, . -. -,.-

--, . ---,..---- --- e..

--, - ---------- ------

1h-. .- --

-- -- --

55 267 -70+5 245 5-- .- ---. -- --

-. . . .--- -- --

-. -- .--- -- --

-. -- --

-- -- -.

-- -- .--- . .-- -- ::

-- -. --

-- -. --

-- -- --

20. IN 110.5621.7M lli.2E.-4- ------. ,- ---.-

.-, - --- ...---- ---#-

1600002 i9.4N 113.4E 76 19. ZN 113.3E

II \71, 13 -5 <0.7h 1)2.5E 80 171

k60600Z 20.3N 113.7E 8. 2(1. W 113.5E 75 13 ‘5 ~3.tIh 113.3E 50 108

MIW; ~l:ill 11$:% j$ ~1:~~ 112:% % 28 -ia ‘~::----- -- ------- .- --

170n00Z 22.7N 114.7E 65 22.6N 114.6E 50 18 .]5 ---- --., - -- --

1706002 23.5N 115. X +n Z3.7N 115.1 E 35 13 ‘5 ‘--- ‘---- ‘- ‘-

1510

-.-.

----- -------=- ---.- .- ... --- ,.--, - .--, .-., - ---------- --..- --- . --- ...

---- ---#--. -.. . ---, -

----- ---.----- ---, ----- ---.’-

---- ---9’--... ....--,. ---,.

..

--$- ---e...- --.c-

-., - .--4.

ii-.----- -------,. -------, - ---.-

191800L 31. ON 127.?E 30 30. ON 127.OE 40 61 10 ‘--- ----- -- ‘-

20017002 32.6N 126.6E 25 32.6N 127.1 E 3S 25 10 ‘--- ----- -- ‘-

2006002 34.7JN 126.1 E 26 3*.lN 126.2E 25 8 0 ---- ----- -- --

-. -- ---- -- -.-- .- --

----- -.-,--.-.

--,- ---.--- ... ---, .

d=mbl&OOL 1? JUl TO 06002 29 .IUL

BEST 7RAC.K UP.RN ING_ EURORS

24 HOUR FORECAS 4a nouk FoREcAs7I FM ~o~s

~~~ti” ZZ.%!s117.9Eu’q8 ~ l~” --------- ‘lY!~NOFOSIT

.-

RORS

80s17

!

----- -.. ,- w!!? ‘o:! Hlwo. -. t

eo 8 >0

~~ lQ? Yo--

.- -- --

-. -. .-. . -- --

-. -. .--- .-. --

-- -. --

. . -. --

. . -- ---. -. --

-- ---- --

-- ---- ---- --

-- ---- ---.

17, Ro13Z 21.%S%IE”% 21.?fi’]~9.1E’’1~:

kaoflooz 22.3N 13a. -w 65 2?. ON ]3a. aE 55

KW881 %:% IW:E ?2 %:u HME %L81RCIOL Z3.5N 13 LE. IE 05 23. vN 137.9E 70

1900002 <+.5N 13a.7E IO(I 24.4N 138.01906002 t5.7N 13B.7E 105 26. UN 137.9 E ;8:

2 6.9N 138.4E 90 26.7N 138.3~?\~8:Z $J.W 138.4, 8. 28.3N 138.+~ %

2000001 t9. SN 138. ~E 65 29.3N 138.3E 75

z8vx8~3!:% 13?:IE2: IU:N IH:% :8201n002 dl.9N 136.7E 5. 32. ~N 136.4E 45

210nn02 32.2N 136.5E 5n 3Z. bN 136.4E 4V

2](16002 32..2N 13b.3E 45 32. uh 136.5.E 2U

?%%~ 28:!1 13i:!E 3: 38::N l:t:!E 3:

231 H(70Z 30.1 N 130. ~E 30 30.lN 130.8E 30

?$1:88;i8:i?N133:% X MN HH N$:128:;M!l m:% 3: 3!::1 %&x 38.25(If700Z dl.7N 129.6E 26 3Z. IJN 129.5E 2525u AnOZ .32.2N 129.9E i?” 3?.3N 129.5E 25

.380+ 002 J2.5N 137.1 E 4s 32.6N 137.2E 40

Zaleooz 33.3N 137.5E 35 33. JN 137.4E 40

z81nnoz d4.1 N 137.5E 25 34. oN 137. *E 40

29unoOZ 3k.6N 137.7E 25 3+. MN 137.5E 3U

I I18 -lu 26.1 N 137.7E 75 99

i? :3 MN 13$:% it M32 15 ?4.3N 136. eE 813 24a

32.3A 136.4E

1f;~~%]~g:~~% 1$ :8

-- ---- --.- --.. - .--. - ---- . :--- - ---- - :--- . ---- - -.-- -.--.- ---. --::-- ---..- ----

-., - ---, --.. . --. ,.3s+0

In

10--

-- .,.-. ... --- .------- ---- --------- ---,--------. ,----.----.-

---- -------- ...-. -,--- ,.-. ---

---- --------- ------- .- --- ,--.---- . . . ...---- -----

. .

.--.--------.---..-. ...-.-..-.

-- -- ..--. ●✎

---.-------.

-- ..--. ...--,.

--------- --.-,-

---- ---<---.- ---+----- --.6-

TI: !~:~~~39:8~ ??~2f

----- -. . . -- . . ..- -----e v ---- ----- -- -- -. ---- -----

-- /.-- ... --- .---- .- --, - --- 4.-

---- -----

-.+- --. ,.

-.+. --. ,-

-----.----------

-.--------- -- -- -- ----- -----

:: ; :::: ----- -- -- -. ---- -----a -b ---- ----- -- -- -- ----- -----

5 3 ---- ----- -- -- -- ---- -----8 15 ---- ----- -- -- -- ----- -----

19 5 ---- ----- -- -- -- ---- -----

---- ---#----- ---f..-. -- ---- . . ---. -. ---- . . :.-. . . ---- -. --

.- .. --- #.---- ---<----- ---.’-

.--.-.. ..- --...-

ALL FORECASIStiA~t.4~;G 26-HR 4M-HN 7 -HR

135NH 70LW4 5~NM

l’lPHOONS WUll E u1hO OvER 35K7SVARNIhG 7A-HR 4EI-HR ~ ;_R

AVEUAGE fOHECAST .%.!OR 17Nv 13=.NM 201Nm E

78

06002 09 &UG TO 1800Z 12 buG

BEST TRACK “ARhlNG

:--- ----- -- -- ---,- ----- -- -- -.:--- ----- -- -- ---.- ----- -- -- -.

L/1y!: HJ::~ :! ‘y! ~:.19.*N 106.1 E 40 28Q Z.O

?J8;M 18W X ?M :f820i3N 106.5E 2S 369 .S

----- ----- -. -. .------ ----- -- -- --

----- ---, - -- -. .------ ----- -- -- .-

-.<- ---, .--+. . . . . . :: :: ::

-., - ----- -- -- -.----- ---.- -- -- -.

~A~N ~~W:E ~~

d

I

7! 7s-.

---- ------ -- -. .-

--, - ------ -- --- . .

---- ------ .- -. -..-m. . . . .. . -- -- -.

----- ------ -- - -.

--... ---,. -- -- ---- ,.. ---,. -. --- .-

---- ------ -- -. ------ ---, - -- -- --

-.. . --. ,.---- ---..-

---- ...*.----- --. ,-

:: --:: ---. -- ---. -. .-

7YP~00NS *HILE MIND OvER 35KTS fiLL FOREchSTS

bvERAGE fORECAST E%lORUARNING 24-14R 4S-flR 7 ‘HR

3WARNING z4-HR 48-HR 72-HR

I 7NM II+NM z55NH ?7 NM 1 W)! 1 &4NM 255NII 279NMAVERME RIGHT ANGLE ERROR 12NH 96NM 225NM 743N)4 I aNM 96NM 225NM ,?+3NM

4VERAG MAGNITUDE OF w ND ERRORE A&VER,SG BIAS OF WINO E ROR %2 -;:[T$ -i%?: -;%!: ?[13 -%% -17!T3 .:3[!2

NUMBFR OF F0REcbST5 15 11 7 1 15 11 7 1

dIEcm06002 10 ●IC 10 12002 17 AUG

BEST 119ACK -24 HOUR FoRECAST 48 MOUH FORECAST 72 09G0 R PORECAST

7oRSWIND POSIT WINO

19 -5 2s.3N 130. IE 50

26 0 ---- ----- --

13 5 26.2N 129.3E 70

01 5 /7.4r4 131.8E

9590

90

J860

55

z~

Ss

45

28-.---.-.

181 1064 30

1? $2

13+ 20

]a :?229 -15

196 -15

M “-!Z

91 5

156 0

323 1:

-- -.U-.<------------.....------.-----------------.<--------::::

----- ----- -. . . -.I

--------------.-,,,.-..---,--.....---..---::::Z+f

---- ---, - -. -- . . ZL.-.. --.(. -.

“-- -- z;--+- ---,. -.---- ---d- -- :: :: *4

25. . .. . .. ...-- -- -., - ----- -- -. -- .-, - .. . ..-- -- ----- ------ -- -- -- ---- :::::-. -- --, - ----- .- -. -- --, -

ALL FO19ECAS7SUAR191NG a4-HQ 4U-14R 72-NR

.- -. ---- -. -.-- -. ---- -- --

79

“s

a.m.

2#,

*#l

#*&..

...

...

!:;:::;:

:;;;::

I$

,,,,

......,.

:;:;1111

,,,,

..

..

::::,0

‘,’,,,,I,,;,

0m

==22OUOOL2 OCT TO ueOuL 10 oCT

REST TRACK 26 UOIJH FOHECASRCRS

PCSIT

h

WIND 0:9 kl~D12.4N 132.7E 5Ui3.lh 131.5E 50 143 ‘5

POSI1 MIND POST T b!i ND

n

I :00200002 11.4u 135.3F 30 11.4N 135.3E 30020&30Z 11. *N 13+.6E 30 11.7N 134.lE 30 1: Q

!111.4h 127. *E 100 227 10

M: i%% ‘:8 ‘~f w

J3. S+ 178.9E 95 56 -50

HM i;21E 133 lU R16.3h 175.8E 120 80 in

15, Ph, l?4.3E 145 13 25

Hm 1?1:%lx?1?: f:15.3A 1713.2E 90 208 -la

lS.5N lln. tk 00

~

96 ,020.lN llR. LL 80 11o LO

:2:,$: !Sy.$: :2 31; ;?

23.3N Ilu. ak 10 47 5

a3.6N ~!:::E ~: 213 -5.- ... -- ------- ----- .- -- :-

-.,. ----- -- .- --

-. ... ----- -- c .- .------ ----- ------- ----- -- -. ::

22.5h lLt,5E23. OB 1L6. OE

---- -------.+- ---..-

---- ,--------, . -. -+..---- .--/----- ---..-.-m - ---,.

IwM im H%% ?! MN lME ?2 y,:091RooZ 22.9M 119. fIE 65 23. QN 119.1 E 75

-., - -------.. . --- a.-

---- .---.’- -. -- -:. . -- ---- -. --

1000oOZ 24. oN 110.4E 6S 23. UN 118.7E 70 20 5

10060 OZ 25.2N 117.7E an 25.3N 117.7E 50 6 10

---- ----- -- -- ------ ----- -- -- --

----- ----- -- -- -- ---- ---d-

----- ----- .- -- -. .-. . ---Q.-

TYPHOONS WHILE MIND ALL FORECh31S

~1200L b 0C7 10 0600L 8 Oc,

EEST TRACK

Pos I 1 Ulwn

821?88;11:NIM U

8R:88\mllHE ?,;8w88?tmllR?E &

0600002 13.2N 111.QE 7P060600Z 13.+N 112.4E 75061POOZ 13.6N 113. nE 70061/ToOZ L4. ON 112.5E 7*

070n00Z i4.2N 111.7E 750706002 14.3N lll.l E 7<

8%881H:% lik’x n080000Z 1+.3N IO LI. QE +5

.3ss5Lw 24 HOUR FoRECAS7 48 uOuk FORECAST-—

F(3S1T ,,,0 *R:%

72 IPOIR s ckEcbsT

PCS17

0

o~:cUbr, b

--.- ------ -- :: ------ . . . .. . . . --

... . ------ -- -- ------ ------ -- -- --

--o- ------ .- -- “-.---- ------ -- .- --

--, - ------ -- .- ----, - -. -.,. .- .- ,, ------ -- .,.. -- -. --

---- ------ -- -- --

--.- ------ -- .- .----- -- .,.- -- -- --

--.- .--..---.- ---..-

i;:;N i;i:~k

lt.2N 107. IE----- -----

1$::: 18%%

14. CN 10R.9L---- --------- ---------- -----

----- --------- -----

-- ..- -----

---- -----

ALL FOI?ECAa TS

1% 2i5 -55

3s z~~ -40-- --

L% 1:4-:8

65 lR 20-- -- ---- -- ---- -- --

-- -- ---- -- --

-- -- ---- -- -- -. .- -.-- -. -.-- -- ---- -- -- --.- ---..-

TYPHOONS WHIIE WZNU OVER 35KTS

bVEOAGE FOREChST ERRORhVERhGE ~1GH7 AN6LF ERRnfJ 12NP “- 89NN ONW e; NM

SKTS f;flS 271(IS12F. M Llghld o NV

AVEQbGE MAGNITUDE OF UINO ERHOR OUTS 5K1SAVEQaGE UIAS OF WIND ERROR

Y2K1S 27KTs1K7S

OKTS6KTS -l IKIS 067S lKTS .6KTs -l IhTs OKT5

NUMRFR OF FORECAS75 15 1; s o is )1 a o

81

06004 6 OCT TO 06002 15 oCT

BEST TaACK WARNING 24 HOUR FoRECAST 40 UOUR FORECAST

i :!

RORs oils

0606002 12. ~is%.lEnl~; 13.%s!:1 .BE’% 25WIND

5 16.%s~~0.1E”’%’ “D 4 ‘~D ,,5.:fis;J;.bE%g 4 -fin

061X10Z 12.9N 14 .9E 3. 13. UN 142.6EI061q00Z 12.9N 14 .7E ~“ 13.lN ,42.,E % ;& = 1;::: i:!:% ;8 I% :1$ it:~ti i%~~ :: 1~~ ~~

070n00Z 12.9N 141.4E 35 13. UN 141.2E &o 13 5 14.lh 139.5E 60 0 15J3N 13i. +E 70 a? To0706002 13.4N 140. RE 45 13. ON 1*0.7E 50 25 5 13.5h 138.5E 70 :;0712002 13.8N 140.4E 55 13.5N 140.2E 55 21

5 13.9N 136. uE 7S 10Q “OO A5. oh 138. ?E 70 50 P 16.4N 136.3E 7s 15Q

071RoOZ 13.9N 139.5E 55 14.13N 139.6E 55 B O 16.lh 137.3E ?0 87 -5 17.8N 134. bE 75 155 ~;

OEX3000Z 14.1 N 138. RE 60 14.lN 13a.7E 60 6 0 45.5h 135.5E 85 33 5 16.8N 135.3E 95 64 45

88!%8; 1*:M W:% 93 M t%:% ?8 H 3 m 133:6[ K in a4 y! W: .3! ;:: $!081 RoOZ h*.lN 136.qE 75 15. ON 137. oE 75 19 0 16.6), 135.lE 90 142 -3q .

0900002 15.1 N 135.qE 8(T 15.2N 135.7E 80 13 0 16.4h 132.5E 90 55 -50 17.6N 130.2E 100 04 5

t64’ I%:$E1]8l?::1$~$8:;~::;~;!:,!~!$m:~13:?:133:% 1?2 1%% HM u 12 ;: ,7:3h091 ROEIZ 15.7N 132. RE 125 15.7N 13?. OE QG O 30 17. Oh 1?9.3E 110 hi.

100noOZ 15.9N 131.7E 140 15.9N 131.7E i40 O 0 ~7.4h 1?8.lE 160 FJS 65 r9.SN 125.6E 14S 183 l@S

18!::83H.:i!i w: M H’:% w! 1% ; ;! p:g p! ~~j ~: g ,:$:M %:% N 1:: l=101 J!OOZ 16.7N 128.1 E 105 16.7N 12 EI. oE 130 -. - ---, - -- --- --

!18288Z i9:?N l$~:zE 2: l?:$N l%::E ial 19 33 hkah 131:% ?’! 18 28 “=:: == = = ::

llti318iW M:*E U lt:flI%$EU ]~A:::h 1)8.lE 65 1----- .- .:: ?!:1: :I$:zf il 38

1201700Z la.6N 1’22.5E 4. la.7N 122.8E 45 5 ---- ----- --1206rIoz la.7N 120. AE 3. 19.4N 120.9E 35 ~~

-- -- 24 .@N lli.7F. 25 629 -55 ---- ----- -- -- -- ---- ----- -- -- .-

121?002 La. ON ha. OE 2S la. UN 119. oE 25 57 0 ---- ----- -- -- -. ---- ----- -- --- --

131?002 17.5N 112.1 E +0 17.5N 112. oE 30 6 -10 ‘--- ‘---- ‘- ‘- ‘- ‘---- ----- ‘- ‘- --

131800Z 17.2N 111. OE 35 17.5N 109.6E 30 82 ‘5 ‘--- ‘---- ‘- ‘- -- ‘--- ‘--=- ‘- ‘- --

140000Z 17. ON 109.9E 30 16.SN 109.4E 30 41 0 ---- ----- -- -- -- ---- ----- -- -- .-

TYPMOONS WHII E WIND oVER 35K7S ALL FORECASTS

“’~;y 341C’ z?%l~” 31i%ERUA~~~~6 ~;~iin @~R :::~~

AVEWAGE FORECAST ERRORAVERAGE MIGHT ANGLF ERRnR 37NM 122NM 170NM

i~~%$~ ~ff~l~!OF1sg #~&8RERR0R

14hM

!Hli R[J2 3$[13 43KTE !Kl$ ?i[lg 39ET$ %la

NUWRFR OF FORECAS7~ 29 22 21 29

&RUTH

1200L 1] OCT TO 1200Z 19 OcT.

BEST TRACK ‘6ARh1N~ 24- HOUR FORECbS7

POSIT WINn POSIT IIINL3 n$?”%i, ‘~%DPo5r7

1500002 14.6N 12*. fiE 7n 14. *N 124.7E 65150hnoZ 14.9N 123.7E 81T 14.9N 123.3E 751517110Z 15.5N I?2.1 E a< 15. *N 122.4E 80151 Rn0Z 15.9N 120.4E 5n 16. UN 120.4E 65

1600002 15.9N 119. OE 60 15. eN 119.1 E 65

1601,170 16.3N 118. nE 65 6.2N 117.9E ?01161700? 16.4N 116. QE 65 6.lN 117. OE 70

161eITOZ 16.7N 115.7E 7fi 16.7N 116. OE 7U

1700002 16. BN 114. sE 8n 16.aN 114.5E 75

t?W81 RN 112:% 82 MN IME U171aoo Z 17. oN 111.6E 90 16.9N 111.4E a5

lannonz 17.2N 1111.9E 90 17.2N 110. aE 85

18!$::; i::% ;ll:% % li:~: il$:$E %IBIROOL 19. IN 109. OE 55 19.2N 109.4E b5

13

I IF

-5 L4.9h l?o.7E 50 115 10s L5.4F! 118. aE so 71 I*

1: .5 16.4h 118.lE 55 69 106 15 ~7.2N 1]6. OE 65 34 -5

0 1-5 17.8k llo. OE 70 I 631-20

22 21 17

48 HOUR F0F4ECA~T,

n

mopsPoSIT uINO U,NLI

12:8N H?:+E ?! w’ i8

II15.w ,M.(E 60 10” -%14JgN 116.uE 55 17* -

17,9N 114.4E 65 13? -R516. aN 112.6E 65 12? -S5

17;2N n?. zE aO 74 .10

il% :W:3* % :2 :;[email protected] IOR.5E 65 46 10

Hl.S. ON IO%dE 40 la6 -10

17.4N 104. uE ~~ Z!: -~-. /. --- . - ~------ ----- -. -- .-

U..... ------.------------------.-..... ---,- -----.<.---------::

191?OOOZ 19.9N 108.4E 5n 19. *N 108.4E 6U 30 10 ‘--- ‘---- ‘- ‘- ‘- ‘--- ‘---- ‘- =- --

H16.4P, 135&2E 75 203 -65 ~14. ah 132J3E eu 129 -6o ~18. kh 134.OE eO 2EI -+0 &19. ah L31. OE 9!3 222 -2s ‘7

18.4h 129. IE 100 I 1631 S .0

la. % 12a.oE ,95 1312 ] 53 fz

-. ,- ---------- ------ ::14:: pi -~~

----- ---,. -- -- .----- ---<. -- -- ------ ------ -. -- .------ .--. ..+ -. -- . .--i- ------ -. -- --.-, . .. . . ... -. .- _-

72 IFOIIR PCRECbSl

RCSIT “DA” fiti:c

113.Oh 10e.OE .7o 1116

IHa WE $: M-.,- .--.,- -. --I---- .--, - -- --

I--4- ---+- -- ---

-. +.- ---,.. -- --

---- .-- . . . .- ---

I---- ----- -- --

-- 25-- -24-- 25-.

‘z&

-- 2.7

I--J-------,..------- ~?q-------d- -- - ---- ..- ---- ..- --- -- --

---- ---, - -. -- .-

*

1%!::2RU}9:% 2: Z1:M;!1:?[ 3: % ]: :::: ::::: :: :: ::----- ----- -- -- -. ---- ------- -. .- .------ ----- -- -- -- ---- .-- . ... -- -- . .

TVPHOONS WHII E uINO OvER 35KTS ALL FORECASTSUARNIF, G 74-H” 48-nR 72-HR WARNING 24-Hil 40-Hk 72-HR

!y~%$~ ~%:$%3~R%40R 1::: ??NH %NR ‘ ‘%%: 1%~ :]NE ‘$%% l$ill~AVEWf,GE fiAGN171)DC OF WIN17 EU160fl 7/(1S 13KTs 16KIS 19KTS 7K S 1 KrS 16KTS 19K ~

AVEOc, GE a!AS OF U WO ERRnR1

3K7S aKTS -SK 1~ -OKT5 3K1S ?KTS ;:K7S -oKTSF. UM. FR OF fORECAS s 33 29 26 21 33 29 21

82

ANNEX A

SUMMARY OF TROPICAL CYCLONES

IN THE CENTRAL NORTH PACIFIC

1. GENERAL RESUME

Fleet Weather Central, Pearl Harbor,issued warnings on two tropical cyclones in1973 for the Central Pacific as shown inTable A-1. Warnings were coordinated withthe Central Pacifi~ Hurricane Center, Hono-lulu, and the Eastern Pacific HurricaneCenter, San Francisco, in accordance withthe National Hurricane Operations Plan.

TABLE A-1. COMPARISON OF CENTWL PACIFICANNUAL WARNING AND CLIMATOLOGY DATA

1969 1970 1971 1972 1973—. —— —

TOTAL NUMBEROF WARNINGS o 27 19 76 43

CALENDAR DAYSOF WARNING o 8 8 21 13

TROPICALDEPRESSIONS o 1101

TROPICALSTORMS o 1130

HURRICANES o 1111

TOTAL o 3342

.2. INDIVIDUAL CASES 1

Two tropical cyclones.entered the Cen-tral Pacific from the east during 1973.Both Doreen and Katherine were ffillydevel-oped hurricanes in the Eastern North Paci-fic before crossing 1406W longitude. OnlyDoreen was still of hurricane intensityupon entering the Central North Pacific.

Doreen, the first hurricane of the yearto invade the Central North Pacific, wasfirst located on 16 July by weather satel-lite near 10”N 101”W over the warm watersoff Panama. Throughout her life cycle,Doreen followed a path strikingly similarto that of Hurricane Celeste of August 1972.

The small storm rapidly intensified tohurricane strength as she moved westnorth-westward toward Hawaii. On the ninth dayafter detection, about 800 miles southeastof Hawaii, Doreen weakened to a tropicalstorm, turned to the southwest, and decel-erated.

On the afternoon of the 27th, the 144-foot Greek ship, CORNELIA, sailed into thestorm’s path and sent out an emergency callfor help when it lost its rudder whilebeing lashed by 50 kt winds and 35-footwaves. A sea level pressure of 971mb was

reported. The ship managed to clear thestorm and continued to Panama after de-ciding not to return to Honolulu with CoastGuard assistance.

After the slowdown, Doreen acceleratedtoward the westnorthwest attaining 85ktwinds near her center. She passed 300 milessouthsouthwest of South Point, Hawaii onthe afternoon of the 30th.

On the afternoon of the 29th, nine-footocean swells and three and a half foot surfgenerated by Doreen were observed at Kapoho,the easternmost town on the island ofHawaii.

On the afternoon of 1 August, a weakDoreen passed 100 miles north of JohnstonIsland. Doreen dissipated under an uppertrough two days later as she crossed theInternational Date Line. No damage was in-curred at Hawaii or Johnston Island.

Beginning as a weak cloud circulationseen by weather satellite on 28 September,Katherine, the second and last CentralNorth Pacific storm of 1973, developed overthe warm waters off Panama in the same areaas Doreen. However, Katherine did not fol-low the same path. She moved towards thenorthwest, intensifying to hurricanestrength”on 1 October, but then curved tothe southwest between 120 and 125”E longi-tude.

Weakening to tropical storm strength,Katherine turned to the southwest on the3rd. By the 6th, she began to follow amore westerly course near 130N 130°W, dissi-pating a few days later 600 miles eastsouth-east of the island of Hawaii under a coldupper trough.

FIGURE A-1. Tkop.i.uzl?S.tohmVoaeen, 28Ju-tg 1973, 2149 GMT. [DMSP .imagaAg)

lReport submitted by Meteorologist in Charge, NWS Forecast Office, Honolulu, Hawaii.

83

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.“t‘+.::’:..:h’;..’:’;..H-’::;.’hy’~’;:‘+~’..“‘:,“:’.“L

.- .0,+01.080.

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...........,

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-1 %+.........y.-. .,..,. .011.021’”””““””.Osl””””“’”’.0?1.,.

.Osl”””’““’”.09,’””““’”.0Lb””.--....-...,.,,,...,....,,,

.081

.-.........,,,~.....,,....,..”

.5—4----++—-+-+

.......-........,..,..,,,.,.,

....~3n~61~M,NM”h*8UI,*.,,.,...............’..’.-::::.-,,.

,,,“%’..

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SOt.4VlS!XIN30Hd..

..,.ltOldOMVUlK3+++-’.............,.-..-’.;“”““””““””’“’”’

.0—--t——+-+.0+30MVEUI11SlalvklldOUl000.0.NGlSS38d30ltiOIdOUlc●*

:.0:t.ok:.0:+.01.k.o-..—

.,.muals1V3ldOlll---‘“’”‘“””““”‘“””““’““”’‘“”

...,,3NvLlluW-1—-.....................~......

,:V:;..::::..::::..:::..::::

ZOOOO/XXlVNOlllSOd3“oz’.....”?!l,.,,..,,,,’O.!’,,..,......1....... ...A11SN3.LNI8

h“:““‘:’‘;‘::‘::”““:’;;’;:““’:’:““’’””““:’‘

*v+.“0?’..........”O.:’.......’.’O:’

.?),’: ...C13MEV””..’”.-“’”‘“”’““”””’”“’”””““””’.s—+--+-+——+———-

$.“””““”’:,;::-+--+-+-SLISOdYOVU11S38UH9~

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,.....

1

aN3931::::::::::::::::::::::::::::::.“:;GLL;+,::::::::?“:::““““”““’’””’““”””,,.,...r t“$-o’-O’--“IW’-WW--Q%L2‘.””’““;09”0- {“”””’““-s‘*&n““” .-.!\!

,..,...!

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85

4. CENTER FIX DATA - HURRICANES

FIuRRICANE DOREENFIx P17s1T ONS Foh CvCLOkL NO

i0601JZ 8 .IIL ro 00U0L UJ AUG4

MaX UUS M6A 0ssFIX F IX ACCli Y FIX

Oas MIN rLTFL I LVL .lNo Src a[NL3 MIN 700qB LVL EYk Onltf”- EvE

R“,G VkL uRG RN(, SLP HGT 11/TO FOINI TAT ION OIA

wok 04PP

N13bNUN 8AFP

3g”N12u”f:# 30 972 285 1> e Clnc 20

1juN‘“”:;2 45 96’

?83 1 f 7 CIRC 23

18 au 310 Mla 96R ?81 10 9 ELIP S,-NbI<ON (3nrP

15X .5

P::N 1 LDI?PDAPP

NUN UAPPNUN DAPP

PCN 1 DAPPv:fiN 1 OAIJP

DAPP

NUN L)APP*CN I IZAVP

P?#’”l WTDCNN2 pm-:

‘UN 80L3A~$ ~

12 967 ?00 10 10 Chic 12

NUN12 8>OA:! 3 962 278 2. II CIRC 10

NUfY oAVPDCN 1 I)APP

DfN I DAPP6> 90 6 994 301 lb 9 CIRC :20

%:h’1 :%F

NU(U l)nPP

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,

‘

86

5. POSITION AND VERIFICATION DATA - HURRICANES

HURR I C6NE DOREEN

16002 17 WI 10 Ooooz 3 bu6

BEST TRACK ,ARN I “G 24 HOUR FoREckST 48 “OUR FoRECAST 72 MIMIR FOHECASI

1900003 11.6N 112. CIW 65 11.6u 112.3u 65

1906002 11.9N 114. OW 70 12. ON 113.5H 7019~200Z 12.1 N 115.lu 75 12.2N 114.7H 100191aoOZ 12.5N 116.W 75 12.6N 116.1* 100

~%%Z ,2.9N ,48.3W 6, 13.3N ,49.0, 75Z 13.lN 147.’4u 60 13.3N 1411. OU 75

2EIW0 12. EIN 148.7w 60 2.7N 148.8u12FJlSOO~ lZ.9N 149.6w 60 2.5N 149.7W

;:

2900002 13. oN 1512.3u 60 13. ON lSO.3d 902906002 13.3N lS1.~W 65 13.lN 151.2u 90

%lg88ZH:$l1%:%R H:?R1%~~!8!300000Z 14. ON 153.7u no 13.9N 153.2M 100

:8!%SZ~::nE%:%% 12:%%:8:1$8301800Z 14.7N 156.6w 85 14.5N 156.8w 90

31000 O2 15. ON 157. %J 80 15.1 N 157.8w 75

3H:88*1%%!i%!:::?:1::3!l%!:?:?g3118002 16.2N 161. flM 65 16.3N 161. *w 75

OIOOOOZ 16.8N 163. ?u 60 16. aN 163.lu 65O1O6OOZ 17.6N 16~.7u 55 17.3N 164. bW 65

8tit881 t~::! 1$9:6: ?g 19:$N 12k?s $$

020000Z 19. oN 16B.7u ●O 18.7N 16b.3U 50

03 SOOOZ 19.5N 17305M 26 19.6N 173.5M 35

0 30 13.6N 153.7d 9012 25 13.7N 154.6ti 90

1+ i~ kJN k%:l: iss30 20 15.4N 156.6u 100

~ ?8 !2::: 133:* 1885 15.6N 160.9u 90

-6 !6.8N 162.1 U 65

1; ~ l?:$N i%:% $324 10 17.9N 166.ZM 65

5 18.7N 169.1 W 651$ 10 19. IN 170.6M 65

5: II lkfx l?s:ti i829 10 20.7N 174.2u 30

43 10 ---- ----- --5 ---- ----- --

25 5 ---- ----- --

6 10 ---- ----- --

189 ‘o 18.4N 16303M 100 296 60

82 . 5 ---- ----- -- -- .- ---- -----

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55

---.-.

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169 30

-- ---- ---- -.

-- -.-- -.-- -.-- -.

-.---..-

-- -.-- -.-- ---- -.-- --

.

NuRR I CAME KATHERINE

lZLIn? 29 5ED tU lbOLtL B oCT

BEST TRACK dARNl ‘JG 24 HOUN FORtCAST ●8 MOWN FoRECAST 72 HOUR FONLCASI

0500602 15.1 N 131 .nw 35 15.7N 129.9w 500506002 14.8N 132. >w 35 15.2N 132.0. 50051?002 1*04N 133.4w 30 15.3N 132.2U 50

0S11300Z 1~.2N 134.5M 30 14.2N 13*.5w 50

0600002 l~. ON 135. au 30 l,.l N 135.6w e<

0 ‘“”N ‘3J”5W~%$1$~ ~~:~~ ]~~:% jO \..6N 1 .7w ::061@ooZ 13.4N 139.lw 30 13. ON 139.8U SO

078 bOOZ 13.3N 140. % 30 12. bN 141. OW070600Z 13. ?N 141.5W 30 12.5N 142. OW

:!

071s 02 13.2N 142..u 3fl 13.1 N 163.2u $(,80710 02 13.1 N 1+3. vu 30 12.9N 144.111 35

%%tl ;::;; ,46.3, 30 13.4N ,4.5.8, 35145.lu 317 13.3N 146.3M 35

OE11200Z 13.3N lIk7. qb’ 25 lJ.6N 148.2w 35

0818002 13. +N 149.7u 2S 13.5N 148. OW 30

P05Y7 UINO13.4N 113.6W 30

16. oN 113.9U 60

t5. otA 115,0d 65

1::2: Iia:t: 28

15..FN 119.5w 55

18.5N 170.0# 75

j::y p::: :$

18. nN 1?3. OU 75

l&l.5N 124. Od 55

la. RN 12.1.7# 5019.,,N 1?5.4u 5515.9N 129.1* 55

J!”:%.33 30 --~-T uIND- . ----- --

47 -5 17.4N llA. UW 6.0

bl -10 19.4N IIA. >w 60

1% :A~ 28:91 112:% 4510+ -35 16.5N 126.2* 50

EIH’WI POSIT WIN()-- -- ---- ---+. --

150 -30 21.2N 116.3w 50

221? -TO 23. ON 116.3ti 60

s?? :~a L%% 112:3: %

23n -;0 16. tiN 129.3w ●5

3S6 -iO 25. ON 122. OU 40

3!3! :2 %% 13?:% :;

3311 40 21. ON 129. OM 50

371 5 21. ON 130.5M 3U

15. ON 137. OU 40

15. !W 1-47.5W 4514.9N 138.74 45

)3. nt. 130.3u 60

,2.5N 141. OG 35

!2:2: 1%?: 3?

12.5N 143.8w 50

)1. uN 1~6.58 5012.5N 147.0# 40

,3. W4 14s02@ 35)3. ON 1.B.2M 35

..+- ----- .----- ----- .----- ----- --------- ...-

92 10 17.5N 14 P.,JR 3S 269

!1 !3 ;~::: !$:::: :! ::2

52 10 12. ON 147. dw 40 119

5 12. ON 14 f.. OW 30 84

,; -: 1?:!1 l%::: 32 i!?:

36 20 11.aN 1~7.IW 50 13~

14; f$ =::----- -. ------- -- --

43 10 ---- ----- -- --63 III ---- ----- -- ‘-

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5*O10

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i::% 1%!: %

15.4N 162.3U 35

---- . . . . . --

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Jywu-- --343 -40

+5.3 -26

221:32

292 -3s

f12 -2

$% J:

771 =

iti *:

514 20

516 0

S5S o51M ~

96 15

86 ltj8s lo

4ZZ -;

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761 ,a

-- .-

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-- --

-- ---- -.

-- ---- --

-- ---- ---- ---- --

88

ANNEX BBAY OF BENGAL TROPICAL CYCLONES

1. SUMMARY OF DATA 1

t ““”’+ p.:. -e%

k5“ ?

,.

,,

T.,T

:’

+

. .

,!. ! , ,-! _!... . ...,!

+

TABLE B-1. 1973 BAY OF BENGAL TROPICAL CYCLONES

CYCLONE

33-73 0835-73 0437-73 1541-73 05

MAx MIN NO. OFINCLUSIVE SFC OBS WARNINGSDATES WND SLP ISSUED REMARKS——

OCT - 12 OCT 40 --- 9 -----------------

NOV - 09 NOV 70 988 13 --------------- --

NOV - 17 NOV --- 4 FORMERLY TS SARAHDEC - 09 DEC :; --- 8 ------- ------- ---

I

lTropical cyclones in the Bay of Bengal are numbered consecutively from the beginning ofthe calendar year and are included with those developing in the South Pacific and Indianoceans. The JTWC area of responsibility in the Bay of Bengal includes the area north ofthe equator from the Malay Peninsula to 90°E. The JTWCissued two warnings in the Bay ofBengal during 1973 when T.C. 33-73 went ashore east of Dacca and when T.C. 35-73 was fore-cast to recurve and move eastward into the JTWC’S area of responsibility. All other warn-ings were issued by FLEWEACEN Guam. All Bay of Bengal cyclones for 1973 are included inAnnex B.

89

bat-.Z

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.

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+,.

+...,.-,+

+..

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++

&+

+.--1-

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‘“”““’1+-4:

uL--2-+

44*-T’

Am

L. LI. .’--.l.1. ../4<:.. . 1....1..1 . ..1

“’~’yc’”i’”-’‘q j, ~5”, ~.~””. BEST TRACK

L

‘:7--:04NOV-09 NOV1973?=’T-M. ‘m. J “’ i \\_w,w,MuM~LpMAX6FC WIND 60 I(TS

NA ,1/ ,,. —

+Jx .1. L. 4!-42 . &Lf?’.Y. ‘,. J ‘L!h.l.” 1 ‘L., J..1In-’, \,(’! I 1) , \, I I I ). I1, 9 hri\V- l15b-

t <“~” k ~ “\’ t 000 TMPICALDISWNICE t t t, .

5“

. . . . . -..

KY

FIGURE B-4. %ebt z%ack chah$ dot TfiopLca2 Cyclone 35-73.

FIGURE B-5. VMSP imageJcqofj8 Novembeh 1’?73, 0243 GMT.

91

Taopicat Cyctone 35-73,

10

w-l_.J~w’+

,,.’

‘ O.O!0

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.. .. .

.i.b

LEGENDsFftDINTENSITYPUSI TION AT XX/6U00ZTSOP I CAL STOSMTSOPICAL DWAESSIOMTROPI CAL D! STURBANCEExTSATROPICALDI SS IPATINQ STAEC

FIGURE B-6. llti~tttackchtuz.t {OE T&opLcal Cyctone 37-73.

●✎

FIGURE B-7. VMSP .LmageJzyo~ Thop.icd Cytione 37-73,16 Novembe~ 1973, 0159 GMT.

92

wi’

w... .

+

I . I la5“

1:X1:’’” .1

1::::1’::1+. L*OJOOZw I ,

t+ . ..+....

‘:[’.-l“’”’1”’’”i”.::i:s*4+’i””!+ ~~

C.. !!T Ic’. ,.;lTIG+I AT xx/00s02 ?’.: k

FIGURE B-8. 8ti-ttnack chcwt ~ofi Taopicat Cgctone 41-73.

FIGURE B-9. DMSP -imagtvuj06 Tkop.kd CycLone 41-73,g Vtzcernbwt 1973, 0621 GMT.

93

3. CENTER FIX DATA

FIxho.

1

23

4567

1011

16

TIME Pn~IT

8ob137 18.6N 927. OE

8 .2137 2@. @N 527.5E18 e137 38. WJ 30. OE

9o013z 5u.7N a33..3E913b13z .98.704 EIO,.5E9 21+2 >8.7N 90 ●,E

i i“9 Ui*Z 58,1W 10 .GE

100U15Z 18. *N 36. I)EJ100b15z 88.7N 35. oE

101216z 58.7N 835. OE101817Z 38.7N 634.5E

1100182 18.7N 434. OE1106182 9LI.7N 33.5EIl1219Z 7EI.6N 533.5Elll&20Z 98.5N 833. oE

1200237 58.5M 234.5E

k~: TIME POSIT

40Q07z se.9N 131.5E

; :%%4;88. UV 83 .5E

338. UW 53 .5E

4 41LI0 z 98. nN 334. !35 50UO?Z 78.aN 33.5 I6 050 blcIz 68.7N 533-nE7 51211z 38.7N 133. oE

51 LI12z lS.6N 633.5E: 60U12Z B8.6N 536. oE

60613z qE.6N 60Z. OE:! 61213Z 88.13N a03. OE

bl@lkZ 4a.7N 303. OE

/: 1%123 ;::i: ‘“m

71?16Z 78. tCN 200.5Eit 71617Z 49.8N 300.5E

IJ $881% %%% ?33::[

80 Ll]Uz 98.8N 133. oE% E1219z 313.7N 933. oE

$4 %t% %m %:%

FIxho. lIME Pfls ] T

1 160015z 38. RN 136. OE

2 1606162 18. RN S04.5E3 161216z 9tT.9N 103.5E

.! 1$1818$ 28:%?83:%6 1706202 29. tN 201.5E7 17082UZ 49.lN 3u1.5E

8 1712217 39.lN 401. OE9 171LW2Z 39.1 N 536. nE

1! l%m 4$::N :%:%

12 1812242 69. ON 933.5E

VN3Pl@L CVCLUNt -FIX POSIT IUNS FW CYCLU#R;: 33-73

u60UZ OU u?T TO UOOUL Id uLT

M,A o.qs ❑AX 08sF 1X ACC14Y FIX FLT LUL UIND *C ● ltiDCAT #AV-MET L“, DIR VFL BOG flNG VEL BUG RNG

SA r

SATSAT

SAT5ATSArSAT

SAT>ATSATbA7

SATSATSATSAT

SAT

(To/o/ / h~s, PCN 3 EIAISP

[To/of / MRS1PCN 3 D16SPPCN 3 DM5P

!: !; : ; ; :%’; ::: j ::;P

IT 0/ (, / / ~RS)PCN 3 DP$PPCN 3 13MSP

f hRs, PCN 3 OMSP[;gclgj/ llRs, PCN 3 u#SP

PCN 3 13#lSP[10/()/ / HRS> PCM 3 DMSP

[To/0/ / IIFJS, Pcti 3 DW3P(70/*/ / IIRs) PCN 3 OMSP

PCN 3 DMSP(1 0/6.0 / / I’lf/s., PCN 3 DAISP

(T 0/6.0 / / MRs) PCN 3 DM5P

SAT

SATSAT

:Al

SA7SAT

5ATSAT

SAT5A T

SATSASA !

Sh TSAT

3:J

SAT5A7SATS4T

(T 0/6.() /

<T o/6. o /

[l $/::: j

(T O/1. U /

(T O/1. U /(T 0/1.0 /

(T 0/1.0 /

/ WJs,

/ hl?s,

$ %!;;/ @RS1/ hRs)/ 71RS)/ liRs)

/ llRS,/ HRs)/ tlRs,

/ hRs ,

~ m;

f tlRs,/ llRs,

PCN 3 OHSP

PCN 3 DMSPPCN 3 OWSP

PCN 3 ENSPPCW 3 DMSPPCN 3 DMSPPCN 3 OHSP

PCN 3 DMSPPCN 3 DNSPPCN 3 DMSPPCN 3 OMSP

PCN 3 DISSP

;f: 3 8%$

PCN 3 DMSPPCN 3 DMSP

%: 3 BE%

PCN 3 ‘sMSPPcN 3 oNSPOCN 3 0W5PPCN 3 OMSP

iTUOP U CYCLLWEFIX POSIT W& F(JR CYCLIJN:% 37-73

.000Z lb NuV 10 ‘WOOZ l“i NUV

OBS MIN rLT FOS17NIN 700M0 Lvl EYE 061 E.N- EVE OF M..SLP HGT 71/10 FORM T.TION Lll A FAO&fi NVOG

*..

00s MIN t LT *POSIT

HA). ORS MAX 08SFIX ACCUY

OBS MIN FLTFIW FLT L*L wINO SFC UIhO

‘FOSIIHIN 700)IB LvL EYE OilEN- EvE OF me,

CAT hAV-HET Lv, DIR VEL 8RG RN6 UEL ONG RNG SLP HGT TL/TU FORM TiTION OIA :17Ao*6 FAlO,fi

TaOPILAL CVCLCANE -FIX POSIT ILINS FOR CrCLONtlN:j 4,-73

VOOOZ 00 U5C TO 120UZ 09 ULC

sl&A o#S MAX OBS OBS MIN +LT

*1x ACCRV FIX71ME

FL1 LVL wIND,Fos1l

SFC MIND MIN 700NB LVI EYEPOSIT CAT hAV-MET Lv#

OUIEN- EYE OFOIR VEL MRG RtiG VEL BUG RNG SLP

m.,HGT 1,/70 FCINM Tj, TION Olb FADAfi NuOh

618 IZ700112 %:% %::/ ::{70612z LW.5N 732.5E SAT71212z 913.5N 534.5E SAT

71U13Z 70. W 336. ISE SAT080U1*Z 68.5N 301. OE MT

0s0615z 6.9. SN 6b;.~[ ~:~081217z 38.6N .

081*1Yz 28. +.N 803. OE ?AT0900202 68. *N 105. oE 5AT

%!:%; ;$:7: %:% ::!

IT 0/1.0 / / hRs,

(7 0/1. ” / / nRs)

~; -g;;::; j :RF;

IT 0/1.() / Z PRS1

(T 0/1.0 / / llRS){T 0/1.0 / / HRs )

(T 0/2. = f / HRS)

{T 0/5.5 / f MRs,(T 0/6.5 / / hRs )

(T 0/7.0 / / HRS)

PCN 3 OMSPPCN 3 OMSPPcli 3 014SPPCN 3 OMSP

PCN 3 OM>PPm 3 DHSP

PCN 3 OMSPPCN 3 OMSP

PCN 3 OMSPOCN .6 DMSP

PCN 3 ONhPDCN 3 DM>P

94

4. POSITION AND VERIFICATION DATA

. . . . . . -.lUl,PICnL CYLLUNL ~~-f>

0bO07 08 OCT TO 00002 12 oCT

REST TRACK W,W51.ING 24 HOUR FORLCASTEIIRORS ERROR=

48 HOUR FOREC6STEl?QooS

72 lbOLR PCtIECbSIEHROQ.

POS J T0EI06002 13. f~s1~8.4E”% 13.lN 88.6E”1%

i0817002 3.2N 88. %E 35 1*. UN 8EI. OE 3SOEIUOOZ 3.3N 08. OE 35 ---- ----- --

‘?; ’180 13.%1 ~6.2Eu1t~

56 0 x6.lh n5.7E 45-- -- ---- ----- --

flCSIT WJAII--- ------- .. .

.$:1u~-c

-- ---- --

-- --

-- -.-- .--- -.

-- --

-- --- -.-- -.

-- -.

-- -.-- -.

-- --

-- . .

--- .--- .’- .. ...----..-------

127 5 15.ON 86.7k 45 2+1 iO

-- -- -----159 20 15.2N ‘ii:::k i; ii; :i

-- -. ----- ----- -- -- --

090n00Z 13.5N 8T. @E 35 13.3N 87. sE 35 21 u 14. ?b n6.1 E ●5

-- -- --.- -----+2 0 1*. +h L16.1 E zi-- -- ---- ----- --

.,. .. . . ...090 f,00Z 13. EN .27. RE 40 ‘--- -----091?OOZ 1+.2N 87.qE 40 13.9N 8T.3E ;;091eoOZ 14.5N 98.1 E 4n ---- ----- --

-4- .-- .,..

------- . . .

--- .---, -

1000OOZ 15.1 N 88.1 E 40 16. *N 88.lE 40

18!588! !Z:iw 8?:% M iGiN -=i:3E ii10lnOO,Z 17.3N 87. *E 35 ---- ‘---- ‘-

42 0 15.4k RB.7E 60

;i ‘; i%k -Gi:;E ::-- -- ---- ----- --

178 2S 16.6N E19.OE 65 464 ‘0

-- .-. . . . .. ----- -- -- --169 15 ---- ----- -- -- .-

-- -- ----- ----- -- -- .-

-.- --------.. .. . . ...-,- .---+..--- ,---d-

---------

I1OOOOZ 18.lN @7. *E 36 17.bN 06.8E 60

HM88Z NM w% n iii%‘~i::E z=

lllriOOZ 20.9N ESCRE 25 ---- ----- --

120000Z 23. SN 85. ?E 25 21.5N 86.8E 3S

229 25 ---- ----- -- -- ---- -. -., - ----- -- -- ----- - --, . ---.- -- -- --

-- -. -. .,- ----- -. -- --

---.-.,-.

.. -

--- .--.+..--- ---------- .--.*,.-,- ---------- .--- .’-149 Ill ----- ----- -- -- -- --, - ----- -- -- --

ALL FORECASTSUARNIN6 74-HR 48-H+(

53AM l;~~~ 7~NM266M I IJNM

4KTS 14KTs 21KTS4KTS }4KIS 21KTS

915

T2.H*

g~

0U15oKTS

o

AVERAGE FORE AST 191ROR$AVEOAGti HIGN ANGLF ENRnP

fiVER40E N@NITl)OE OF WIND ERNORbVE.Q&GE MIAS OF III% ERROR

NUMnER of FORECAST%

TRl<PICbL CYCLONE 35-73

0000Z 04 NOV TO 12002 09 NOV

BEST TRACK uARNING 24 HOUN fOMt.CASTERRORS

48 HOUH FORECASTERRORS EFtRooS

72 O-OUR FC14EC4STERROU.

‘% “’g” 7.%S’J7.1E’”4%-- -- ---- ----- --

~~ o 8.9N P4.8E y-- ---- -----

PCSIT--- .---a.. w:? ,mjWI*C

-.-- -.----- ::

-- --

-- -.

-- .--- --

-- ---- -.-- -.

-- -.

-- -.

:: -.-.

-- --

-- --

-- ---- -.-- --

-- --

-- -- ----- -----197 0 ,9.8N y:~E-- -. ----

-. - ----...::: ::::q:.-.. .-.-/.--- .---#-

..----.. -.. .---.. .,-.---..-.-...-,--..----------..-.. .---.-.

i54 -10 9.8N R2.5F. 658 -lU 14.3N RG.2E 70

39 -5 15.3A SE.4E 75-. -- ---- ---, - --

295 .5 10.eN 79.lE110 10 le. ]N 81S. St

129 15 19. oN e%fk-- -. ----- -----

--- ,---d-- . . ---- ...

a9 O 17. zk 89.lE 75-- -- ---- -----42 10 17. @h F16.6E ii

-- -- ---- ----- --

144 20 20d5N 9fI.dk-- -. ----- -----

112 2S 21. ON 87. bE

-- -. ----- -----

99 25 ---- -----

3TG ‘-’- ~~::~-i ----

-- -. ----- -----

-- -. ---- -----

-- -- -- ..- ------- -. -- .,- ------- -. -. . .. -----

-- -- -. . .. ---.-

00 194 ,50601700Z 12. EIN 86. %E 60 13.4S4 87.9E 6006vf,00Z 13.3N E16. *E 60 ‘-. ? -----061700Z 13.aN 86. #E 60 14. dN 86.2E ii

-.- ----...-- .-80 10? :;

--- .---, --.. .. . . ...061RoOZ 1+.4N 87.3E 55 ---- ----- --

070000Z 15.2N 07.7E 55 15. *N 86.4E 80

8?VXW *]N g%% ~~ iZiN %?:SE 73

. . -. ---- .- --

-,- ..--,.-.- -------

-. -. ..-. -- -. --- ...- ,.-,- ----/.-. .- --. . -- --

--- --------- .---<-

OTIROOZ lT.4N 88.3E 50 ---- ----- -- -- -- -- -

000nOOZ 18*2N GLI.3E 45 19.3N 90.2E 70 ,26 25 ----

88!9:8~ 18::N 8?:JE :: 2!::N -?!:% !! ‘2Z 1? ::::OGIJ?OOZ h9.7N e7.5E 30 19. eN ea.9c 55 7!3 25 ----

090000Z 20.2N 86.QE 25 19.5N 88.5E 55 99 30 ----

--- .- ------- ------- .------ -- -- -- .--- -- -- --- --------.. .. . . ...----- ----- .- --

-- -- ---- -- --

--- .---, ---- .---, .

AVEQAGE FOUECAST EQRORAVER4GE RIGHT ANGLF ERRoR

i![%g~ ~!i~]~l%fl~ ~A:~RERnoRNLN07ER 0$ FORECAS7S

95

TR(’PIchL CYCLONE 37-73

00002 16 Nov 10 Omooz 17 Nov

BEST TRACK wARF,lffi 24 HOUR FoRkChST 48 HOUR FoRECAST 72 lF~R 6CRLC4ST

POSIT WINQ POSIT WIND “~~R%D POSIT U~ND Oi~’’fi%O ;0S[1 MINO D~?mi?;~u llCSIT MIMD O~!Rg:iC160nu0Z 15.3N 130.1 E 50 15. ON 87.9E 69 21 10 16.5N F16.8E 75 274 20 ----- ----- -- -- -- --- ----- -- -- . .

RLL FORECAal SdAiTNING z4-HR bu-wn 72-tIu

TR<PICbL CVCLONk 4i-73

OUO02 06 OEC TO 12002 09 DEC

BEST TRACK wARI! IMG 24 HOUR FoRECAST 48 HOUR FORECAST 72 IWOUR PCRE caSl

S4CSIT UOF.OPOSIT UIND IJosl T MIND0600002 9.7N OT.~E 35 T.lN 8T. OE 60

8Wf48~ 18:1N 81:3 t! RN 8?:Z+ 4$061 REIOZ 11.2N 8b.6E 50 ---- ----- --

,&w” 1. c-- --

-- ---- ---- --

-- .-

-- ---- ---- -.

-- -.

-- ---- ---- -.

-- -.-- -.

-- --

-o-

----,-

-------- ,.--- ...--- ,.-

.-

.-.-

.-

.-

.---

.-

S3 -10 13.9k R7.lE 50 112 -10 M.TN 14R.2E 65 293 ,S

.-.17: ‘; iF~jN ‘i~:;E 6s S;; ;;

-- -. ----- ------ .- -- -.

-..-------+-

--- /.-- -- -., - -----31 -15 15.2k 83.9E ii-- -- ---- ----- --

--- P--- #.---..

080n00Z 14.6N B5.3E 60 14. ON 85.lE 60

%%+ i%% %:fi: 2? ii:iN ‘i;:5E ;;081ROOZ 19.2N tT6. RE S5 ---- ----- --

30 0 15..8h 84.6E 65

5 19.2N ‘i; :;E i;i? ‘- “-”--- -- ---- ----- --

301 1s ----- ----- -- -- --

-- . . ----- . . . . . -. -- --396 3S ----- ----- -- -- -.

- -. .. . ... . . . . . -- -- .-

.*--#--,----

--- ●

✍✍✍✌✎

✍✍✍✜✍✍✍✎✌✎

--.-

& o ---- ----- ::-- ---- -----

B lU --, - ----- --

-. -. ---- ----- -- -- -.-- -- -- ... --- .- -- -. ---- _ ---- ---a- -- --- --

.-.o -

---

-*. -

----....--- .’----- ...

-..-

96

APPENDIX

ABBREVIATKINS AND DEFIWTIONS

The following abbreviationsand defini-tions apply for the purpose of this report.

1. ABBREVIATIONS

ACGW

AIREPS

AJTWC

APT

AWN

CINCPAC

CINCPACAF

CINCPACFLT

CINCUSARPAC

DAPP

DMSP

Aircraft Control and Warn-ing

Commerical and MilitaryAircraft Weather Report

Alternate Joint TyphoonWarning Center (AsianTactical Forecast Center,Fuchu, Japan)

Automatic Picture Trans-mission

Automatic Weather Network

Commander in Chief, Pacific

Commander in Chief, PacificAir Forces

Commander in Chief, PacificFleet

Commander in Chief, U.S.Army Pacific

Data Acquisition and Pro-cessing Program (RenamedDMSP)

Defense MeteorologicalSa-tellite Program

ENVPREDRSCHFAC EnvironmentalPredic-tion Research Facility

NESS

NWS/NOAA

PACOM

SLP (MSLP)

TCRC

WMo

(NavalPostgraduateSchool,Monterey, California)

National EnvironmentalSa-tellite Service (Suitland,Maryland)

National Weather Service,National Oceanic and Atmos-pheric Administration

Pacific Command

Sea Level Pressure (MinimumSea Level Pressure)

Tropical Cyclone Reconnais-sance Coordinator

World MeteorologicalOrganization -

2. DEFINITIONS

CYCLONE - An atmosphericclosed circu-lation rotating counterclockwisein thenorthern hemisphere.

TROPICAL CYCLONE - Aclone of synoptic scale,tropical or sub-tropical

non-frontal cy-developing overwaters and having

a definite organized circulation and warmcore.

TROPICAL DEPRESSION - A tropical cyclonein which the max~mum sustained surface windis 33 kt or less.

TROPICAL STORM - A tropical cyclonewith maximum sustained surface winds in therange 34 to 63 kt inclusive.

TYPHOON/HURRICANE- A tropical cyclonewith maxzmum sustaxned surface wind s~eeds64 kt or greater. West of 180 degree;longitude the name TYPHOON is used and eastof 180 degrees longitude the name HURRICANEis used. All descriptivereferencesto ty-phoons apply equally to hurricanes.

SUPER TYPHOON - A typhoon with maximumsustainedwinds greater than or equal to130 kt.

TROPICAL DISTURBANCE - A discrete sys-tem of apparentlyorganized convection,generally 100 to 300 miles in diameteroriginating in the tropics or sub-tropics,having a non-frontal migratory characterand having maintained its identity for 24hours or more. It mayor may not be asso-ciated with a detectableperturbationonthe wind field. As such, it is the basicgeneric designationwhich, in successivestages of intensification,may be subse-quently classified as a tropical depres-sion, tropical storm or typhoon.

EYE/CENTER - EYE refers to the roughlycircular central area of a well-developedtropical cyclone usually characterized-bycomparativelylight winds and fair weather.If more than half surroundedby wall cloud,the word EYE is used; otherwise, the areais referred to as a CENTER.

WALL CLOUD - A densely organized,roughly circular’structureof cumuliformclouds completely or partially surroundingthe eye or center of a tropical cyclone.

MAXIMUM SUSTAINEDWIND - Highest sur-face wind speed of a cyclone averaged overa one minute period of time.

EXTRATROPICAL- A term used in warningsand tropical summaries to indicate that acyclone has lost its “tropical characteris-tics.” The term implies both poleward dis-placement from the tropics and the conver-sion of the cyclone’s dominant energy sourcefrom latent heat of condensationrelease tobaroclinic processes.

TROPICAL CYCLONE RECONNAISSANCECOORDI-NATOR - A CINCPACAF representativedeslg-= to levy tropical-cycloneweather -reconnaissancerequirementson CINCPACAFreconnaissanceunits within a designatedarea of PACOM and to function as a coordi-nator between CINCPACAF,weather reconnais-sance units, and JTWC.

97

AFGWC (2)BUR OF MET, AUST (1)AMER EMB BANGKOK (1)CATH UNIV OF AMERICA (1)CENWEABUR TAIWAN (2) - “CHIEF, MAAG TAIWAi ~1)CHINESE AF WEACEN TAIWAN [3)CHINESE NAV WEACEN TAIWAN-(il. .CINCPAC (2)CINCPACAF (1)CINCPACFLT [SlCINCUSARPAC’(i)CIVIL DEFENSE (GUAM) (2)CNO (2)COLOiAiM3STATE UNIV (LIBR) (1)COLORADO STATE UNIV (MET) (1)COMCRUDESPAC (1)COMINFLOT ONE (1)COMNAVFACENGCOMPACDIV(1)COMNAVMARIANAS (1)COMNAVWEASERVCOM(10)COMPHIBPAC (1)COMSEVENTHFLT (1)COMUSTDC (1) ‘ -CPF (1)CSG (1)CLSF (1)CSSF (1)CAF [1)CACSF _fllCASWF iHtiE (1)CGFMF (1ICOMSC (ljCOMTHIRDFLT (1)COMUSNAVFORJAPAN(1)COMUSNAVPHIL (11DDC (10) - -DIA (1)DIR OF MET SAIGON (1)ECAFE (2>EDS (D:4j (1)8 AF/DOO (1)ENVP~DRSCHFAC (4)FAA (CERAP) (2)FLENEMWEACEN [11FLEWEACENNORFOLK (1)FLEWEACEN PEARL HARBOR (1)FLEWEACEN ROTA (1)FLEWEAFAC SUITLAND (1)GEN MET DEPT THAILtiD-(l)HQ AWS (3)HQ, 1ST MARINE ACFT WG (1)

DISTRIBUTION

HQ, lWWG (15)HQ, 3WWG (1)HO. 9WRWG [21INDIA MET DEfiT(1)JAPAN MET AGENCY (1)LIBR OF CONGRESS (2)LIBR OF CONGRESS (EXCHANGE& GIFT DIV) (4)LOS ANGELES PUBL LIBR (1)MCAS IWAKUNI (2)MCAS KANEOHE BAY (1)MUDEFASSTOFFICEJAP~ (1)NASA (1)NATWEASERV PACREG (2)NWSFO HONOLULU (1)NAVAL ACADEMY (1)NAVOCEANO (2)NAVPGSCOL (DEPT OF MET) [2}NAVPGSCOL (LI)3RARY)(lj - -NAVWEASERFACALAMEDA (1)NAVWEASERFACJACKSONVILLE (1)NAVWEASERFACSAN DIEGO (1).,NESS (2)NHRL (2)NHC (2)NWSED ASHEVILLE (2)NWSED ATSUGI (1)NWSED BARBERS POINT (1)NWSED CUBI POINT (1)-NWSED IWAKUNI (1)NWSED NAHA (1)NWSED YOKOStiti(1)ODDR&E (1)OKINAWA MET OBS [1)OL A, 10WSQ (1) - -OL B, lWWG (4)PAGASA (3)ROYAL OBSERVATORY f31TEXAS A&M (1) ‘ -TYPHOON COMM SECR (1)TTPI (1)UNIV OF GUAM (1)UNIV OF HAWAIi lDEpT OF MET) (2)UNIV OF HAWAII (LIBR) [11UNIV OF MEXICO /1) - - -UNIV OF PI (1) ‘ ‘VQ-1 (1)WEARECONRON FOUR fl>20WSQ (11) ‘ ‘53WRS (2)54WRS (10)55WRS (2)3345TH TECH SCHOOL (1)

e

98

UnclassifiedECU RITV c1 D.SSIFICATIn N nc TLIIC =Acc ,u%.- n.,. =-.--A,------- .. .. .. ,. -,.- . . ...-.-w- ,-......----.-.0 .-.-”,

REPORT DOCUMENTATION PAGEREAD INSTRUCTIONS

BEFORE COMPLETING FORM1. REPoRT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER

Annual Typhoon Report 1973).TITLE (end Subfftie) 5. TYPE OF REPORT & PERIOD COVERED

Annual (JAN-DEC 1973)ANNUAL TYPHOON REPORT 1973

s.F’ERFORMINGORG. REPORT NUMBER

AuTHOR(S) 8. CONTRACTOR GRANT NUMBER(aJ

PERFORMING ORGANIZATION NAME ANO ADORESS 10. PRoGRAM ELEMENT,PROJECT, TASKAREA& WORK UNIT NUMBERS

FLEET WEATHER CENTRAL/JOINT TYPHOONWARNING CENTER [FLEWEACEN/JTWC), GUAM FPOSAN FRANCISCO 966301.CONTROLLING OFFICE NAME ANO AODRESS 12. REPoRT OATE

FLEET WEATHER CENTRAL/JOINT TYPHOON WARN- 1973ING CENTER (FLEWEACEN/JTWC), GUAM 19.NuMBER OF PAGES

FPO SAN FRANCISCO 96630 984.MONITORING AGENCY NAME & AOORESS(ff different fmnl Confrofffng Office) 1S. SECURITY CLASS. (oftfdareport)

UNCLASSIFIED\Sa. DECLASSIFICATION/DOWNGRADING

SCHEDULE

5. DISTRIBUTION STATEMENT (ofthfaReport)

Approved for public release; distribution unlimited.

~.DISTRIBu TlON STATEMENT (of the abatmct antemdln Block 20, lidifftwmt fmca Report)

1. SUPPLEMENTARY NOTES

KEY ~OROS (Contln.eon revera. aide ffnecoaew mdidentlti tiblockn-bar>

rroplcal cyclones Analog forecastinghopical cyclone forecasting Tropical Cyclone Researchryphoons Tropical Stormsryphoon forecasting Tropical depressions

Super typhoons‘.ABSTRACT (ConNnueon reveree ●ide ffnecaaaary aadfdantlfy by block number)

Annual publication summarizing the tropical cyclone season inthe western North Pacific, Bay of Bengal,?acific.

and the central NorthA brief narrative is given on each typhoon in the

restern North Pacific including the best track. Pertinent recon-naissance data used to construct the best tracks are provided.?orecast verification data and statistics for the JTWC aresummarized. Research efforts at the JTWC is discussed briefly.

—— can” -.——DD ,j;;;3 1473 EO1710N OF 1 NOV6S IS OBSOLETE

S/N 0102-014-6601 UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE (WA-n Dataf!nta-d)

ECURITY CLASSIFICATION OF THIS PA GE-(W%en llafa Entered)

SECURITY CLASSIFICATION OF THIS PAGEfW%en Data Entered)

i /. .,,

1 1 7

L-:c‘~~~I 1 I./,,,, . ,,, ..,, ,

+

,,. !60. ,50. ‘“.

,..

+–130— 30 ,0 30

:“::;4; :4::::::. . . . . . ..,, :’. .’::. ,: ::.. . . ..l~/./.4.... ... .,,,,,

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1 EDGE INDEXHOW TO USE THE EDGE INDEX \

OPENTHERE.

Bed the book nearly doubleand hold it in your right handas shown.

Locate the listing you wantin the Edge Index.

Match up the 1or2 line syrmM nexttothelistingyouhaveselectedwiththecor.responding1or 2 dot symbolon the page adge.

I

CHAPTER I Operational Procedures

CHAPTER IIReconnaissance and

CommunicationJ

CHAPTER Ill R&search Summary I

CHAPTER IV Summary of Tropical Cyclones

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Summery of ForecastCHAPTER v verification Data

ANNEX A Summary of Tropical Cyclones

in the Central North Pacific

ANNEX” B Bay of Bengal Tropical CyclonesI

APPENDIXAbbreviations, Definitions

and Distribution

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united states navy...vector mean charts (crutcher, h. l., 19731. (3) north indian tropical cyclone...

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