matthew cote, lance bosart, and daniel keyser state university of new york, albany, ny

11

Predecessor Rainfall Events (PRE) in Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Tropical Cyclones - Results from a

Recent Northeastern U.S. Collaborative Recent Northeastern U.S. Collaborative Science, Technology, and Research Science, Technology, and Research

(CSTAR) Project(CSTAR) Project

Predecessor Rainfall Events (PRE) in Predecessor Rainfall Events (PRE) in Tropical Cyclones - Results from a Tropical Cyclones - Results from a

Recent Northeastern U.S. Collaborative Recent Northeastern U.S. Collaborative Science, Technology, and Research Science, Technology, and Research

(CSTAR) Project(CSTAR) Project

Matthew Cote, Lance Bosart, and Daniel Keyser

State University of New York, Albany, NY

Michael L. Jurewicz, Sr.

National Weather Service, Binghamton, NY

July 10, 2008 – HPC, Camp Springs, MD

Matthew Cote, Lance Bosart, and Daniel Keyser

State University of New York, Albany, NY

Michael L. Jurewicz, Sr.

National Weather Service, Binghamton, NY

July 10, 2008 – HPC, Camp Springs, MD

22

OutlineOutlineOutlineOutline

• Data Sources

• Definition of PRE

• Motivating factors / goals for this session

• Methodologies for the project

• Categorize PRE / Establish climatologies for the Eastern U.S. / Atlantic Basin TC

• Provide operational forecasting resources

– Composites / Conceptual models

• Case Study Examples

• Summary

• Data Sources

• Definition of PRE

• Motivating factors / goals for this session

• Methodologies for the project

• Categorize PRE / Establish climatologies for the Eastern U.S. / Atlantic Basin TC

• Provide operational forecasting resources

– Composites / Conceptual models


• Summary

33

Data SourcesData SourcesData SourcesData Sources

• WSI NOWRAD Radar Imagery

• HPC Surface / Radar Analyses

• SPC Upper-Air / Mesoanalyses

• Archived TC Tracks / Positions from TPC

• NARR 32-km Datasets

• NWS WES Imagery

• NPVU QPE Data from NWS RFC’s

• WSI NOWRAD Radar Imagery

• HPC Surface / Radar Analyses

• SPC Upper-Air / Mesoanalyses

• Archived TC Tracks / Positions from TPC

• NARR 32-km Datasets

• NWS WES Imagery

• NPVU QPE Data from NWS RFC’s

44

PRE – What are They ?PRE – What are They ?PRE – What are They ?PRE – What are They ?

• Coherent areas of heavy rainfall observed poleward of Tropical Cyclones (TC)

– Distinct from the main precipitation shields of TC, or their extra-tropical remnants

– Yet, still indirectly tied to TC

• Coherent areas of heavy rainfall observed poleward of Tropical Cyclones (TC)

– Distinct from the main precipitation shields of TC, or their extra-tropical remnants

– Yet, still indirectly tied to TC

55

PRE Example – Frances (2004)PRE Example – Frances (2004)PRE Example – Frances (2004)PRE Example – Frances (2004)

Main Precipitation Shield of the TC

PRE

66

Results of the Frances PREResults of the Frances PREResults of the Frances PREResults of the Frances PRE

77

Motivation for Research Motivation for Research Motivation for Research Motivation for Research

• PRE can be particularly challenging phenomena for operational meteorologists

– NWP models often underestimate / misplace heavy rainfall associated with PRE

• Poor handling of diabatic heating transfer / upper-jet intensification

– Attention is frequently diverted to different areas / times

• Closer to where TC make landfall

• Future time periods when the more direct impacts of TC or their remnants may be expected

• PRE can be particularly challenging phenomena for operational meteorologists

– NWP models often underestimate / misplace heavy rainfall associated with PRE

• Poor handling of diabatic heating transfer / upper-jet intensification

– Attention is frequently diverted to different areas / times

• Closer to where TC make landfall

• Future time periods when the more direct impacts of TC or their remnants may be expected

88

GoalsGoalsGoalsGoals

• To provide NWS forecasters / operational meteorologists with:

– Background Knowledge / Awareness of PRE

– Forecast Tools

• PRE Climatologies

• Conceptual Models / Composite Charts


• To provide NWS forecasters / operational meteorologists with:

– Background Knowledge / Awareness of PRE

– Forecast Tools

• PRE Climatologies

• Conceptual Models / Composite Charts


99

Methodology Methodology Methodology Methodology

• We restricted classifications of PRE to systems that met the following criteria:

– 100 mm (4”) of rainfall needed to be observed within a 24-hour period

– Such rainfall had to be connected with a well defined region of precipitation

• Not scattered / isolated convection

• We restricted classifications of PRE to systems that met the following criteria:

– 100 mm (4”) of rainfall needed to be observed within a 24-hour period

– Such rainfall had to be connected with a well defined region of precipitation

• Not scattered / isolated convection

1010

Frequency of OccurrenceFrequency of OccurrenceFrequency of OccurrenceFrequency of Occurrence

• Our period of study ran from 1998 to 2006

• 47 PRE were identified, which were tied to a total of 21 TC

– An average of about 2 PRE per PRE-producing TC (PPTC)

• About 1/3 of all Atlantic Basin TC that made U.S. Landfall for this period were PPTC

– A few outlier PPTC did not actually make landfall

• Our period of study ran from 1998 to 2006

• 47 PRE were identified, which were tied to a total of 21 TC

– An average of about 2 PRE per PRE-producing TC (PPTC)

• About 1/3 of all Atlantic Basin TC that made U.S. Landfall for this period were PPTC

– A few outlier PPTC did not actually make landfall

1111

Separation DistanceSeparation Distance

1086 1086 ±± 482 km 482 km Median: 935 kmMedian: 935 km

Bosart and Carr (1978) conceptual model of antecedent rainfall indirectly associated with TC Agnes (from 1972)

PRE StatisticsPRE Statistics

Agnes PRE

1212

Separation Distance

1086 ± 482 km Median: 935 km

Event DurationEvent Duration

14 ± 7 h Median: 12 h


PRE Statistics (Continued)PRE Statistics (Continued)

Agnes PRE

1313


PRE Statistics (Continued)PRE Statistics (Continued)

Separation Distance

1086 ± 482 km Median: 935 km

Event Duration

14 ± 7 h Median: 12 h

Time LagTime Lag

45 ± 29 h Median: 36 h

ROT AT

LOT

1414

PRE Locations Relative to TC Track (1998-2006)

0

5

10

15

20

25

30

PRE Left of TC Track PRE Along TC Track PRE Right of TC Track

Relative Locations

Num

ber

of P

RE

s

PRE Track-Relative PositionsPRE Track-Relative Positions

26

129

1515


0

5

10

15

20

25

30


Relative Locations

Num

ber

of P

RE

s


26

129

Potential for excessive flooding beginning before arrival of TC rainfall

1616


0

5

10

15

20

25

30


Relative Locations

Num

ber

of P

RE

s


26

129

Potential for flooding in areas not directly impacted by TC rainfall

1717

Further Sub-ClassificationsFurther Sub-ClassificationsFurther Sub-ClassificationsFurther Sub-Classifications

• Separation by Similarity of TC Track:

– Southeast Recurvatures (SR)

• Highest percentage of PPTC

– Atlantic Recurvatures (AR)

• Most common TC Track

– Central Gulf Landfalls (CG)

• Lower percentage of PPTC, but high frequency PRE production within those PPTC

– Other “Hybrid” TC that were harder to categorize

• Separation by Similarity of TC Track:

– Southeast Recurvatures (SR)

• Highest percentage of PPTC

– Atlantic Recurvatures (AR)

• Most common TC Track

– Central Gulf Landfalls (CG)

• Lower percentage of PPTC, but high frequency PRE production within those PPTC

– Other “Hybrid” TC that were harder to categorize

1818

SR TC Tracks and PRE LocationsSR TC Tracks and PRE LocationsSR TC Tracks and PRE LocationsSR TC Tracks and PRE Locations

All SR TC Tracks All SR PPTC Tracks; with PRE centroids (colored dots)

1919

AR TC Tracks and PRE LocationsAR TC Tracks and PRE LocationsAR TC Tracks and PRE LocationsAR TC Tracks and PRE Locations

All AR TC Tracks All AR PPTC Tracks; with PRE centroids (colored dots)

2020

CG TC Tracks and PRE LocationsCG TC Tracks and PRE LocationsCG TC Tracks and PRE LocationsCG TC Tracks and PRE Locations

All CG Tracks All CG PPTC Tracks; with PRE centroids (colored dots)

2121

Favorable Locations for PRE Favorable Locations for PRE Favorable Locations for PRE Favorable Locations for PRE

• Within the Right-rear quadrant (RRQ) of an Upper-level Jet

• Ahead of the Mean Long-Wave Trough Axis at Mid-levels (trough axis is west of the parent TC’s longitude)

– Near or just upstream from Short-wave Ridging

• Near a Low-level Front / Baroclinic Zone

• On the periphery of a Tropical Moisture Plume

• Near or just west of a Low-level Theta-E Ridge Axis

• Within the Right-rear quadrant (RRQ) of an Upper-level Jet

• Ahead of the Mean Long-Wave Trough Axis at Mid-levels (trough axis is west of the parent TC’s longitude)

– Near or just upstream from Short-wave Ridging

• Near a Low-level Front / Baroclinic Zone

• On the periphery of a Tropical Moisture Plume

• Near or just west of a Low-level Theta-E Ridge Axis

2222

SR PPTC Composites (PRE - 12)SR PPTC Composites (PRE - 12)

Center of composite TC

Trough axis

Ridge axis

θe-Ridge axis

700 mb heights (dam) and upward vertical motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds

(shaded, m s-1)

2323

SR PPTC Composites (At Time of PRE)SR PPTC Composites (At Time of PRE)

700 mb heights (dam) and upward vertical

motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds (shaded, m

s-1)Center of composite TCCentroid of 1st composite PRE

Trough axis

Ridge axis

θe-Ridge axis

2424

SR PPTC Composites (PRE + 12)SR PPTC Composites (PRE + 12)


Centroid of 1st composite PRE

Centroid of 2nd composite PRE

Trough axis

Ridge axis

θe-Ridge axis

700 mb heights (dam) and upward vertical motion

(shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds

(shaded, m s-1)

2525

Common Detracting Elements for Common Detracting Elements for PRE FormationPRE Formation

Common Detracting Elements for Common Detracting Elements for PRE FormationPRE Formation

• A Zonal Flow Pattern is in place Poleward of the TC

– Lack of merdional flow discourages northward return of deep tropical moisture away from the TC itself

• The Long-wave Mid-level Trough Axis is already east of the TC’s Longitude

• A Low-level Blocking Ridge is located north / northeast of the TC

– Tends to prevent significant moisture inflow into any frontal boundaries or jet circulations that may be poleward of the TC

• A Zonal Flow Pattern is in place Poleward of the TC

– Lack of merdional flow discourages northward return of deep tropical moisture away from the TC itself

• The Long-wave Mid-level Trough Axis is already east of the TC’s Longitude

• A Low-level Blocking Ridge is located north / northeast of the TC

– Tends to prevent significant moisture inflow into any frontal boundaries or jet circulations that may be poleward of the TC

2626

SR Null-Case CompositesSR Null-Case CompositesSR Null-Case CompositesSR Null-Case Composites

700 mb heights (dam) and upward vertical motion (shaded, μb s-1)

925 mb heights (dam), θe (K), and 200 mb winds (shaded, m s-1)


2727

Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)Case Study (TC Erin, 2007)

• CG Landfall PPTC

– Several PRE were associated with Erin (typical of CG PPTC)

• Erin’s PRE exhibited many of the “classic” synoptic-scale ingredients

– Within RRQ of an upper-level jet

– Deep moisture was fed northward into the PRE / pronounced theta-e ridging developed

– A low-level boundary was in the vicinity

• CG Landfall PPTC

– Several PRE were associated with Erin (typical of CG PPTC)

• Erin’s PRE exhibited many of the “classic” synoptic-scale ingredients

– Within RRQ of an upper-level jet

– Deep moisture was fed northward into the PRE / pronounced theta-e ridging developed

– A low-level boundary was in the vicinity

2828

Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)Track of Erin (Aug. 15-20, 2007)

18/12z

19/00z19/06z

19/12z20/00z

2929

Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)Multiple PRE Producer (First 2 PRE)

PRE #1 – 3-6” (75-150 mm) of rain late on 8/17/07 (“Along-track” PRE)

PRE #2 – 4-8” (100-200 mm) of rain early on 8/18/07

3030

Erin’s 3Erin’s 3rdrd PRE PREErin’s 3Erin’s 3rdrd PRE PRE

Locally 10+ “ Locally 12+” (300+ mm) of

rain on the evening of

8/18/07

3131

Ramifications of PRE #3Ramifications of PRE #3Ramifications of PRE #3Ramifications of PRE #3

• 12” - 15” of rain fell in 6 hours or less over parts of Southeastern MN and Southwestern WI

– Record flooding

– Several fatalities

• 12” - 15” of rain fell in 6 hours or less over parts of Southeastern MN and Southwestern WI

– Record flooding

– Several fatalities

3232

Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07Water Vapor – 02z, 8/19/07

Significant PRE

Erin’s Moisture Plume

MSLP Isobars and Mean 925-850 mb Winds

L

TD Erin

3333

300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07300 mb Analysis – 00z, 8/19/07

Jet Entrance Region

PRE

3434

850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07850 mb Moisture Transport - 00z, 8/19/07

L

PRE

TD Erin

3535

Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07 Surface Analysis + Radar - 00z, 8/19/07

PRE

3636

Flooding PicturesFlooding PicturesFlooding PicturesFlooding Pictures

3737

Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)Null-Case Study (TC Gabrielle, 2007)

• Became a Tropical Storm over the western Atlantic, before brushing the Outer Banks of NC

– Then recurved towards the east-northeast over the open Atlantic (Would be categorized as an AR TC)

• No PRE were associated with this TC

– Expansive ridge axis blocked advection of deeper moisture into the U.S.

• Became a Tropical Storm over the western Atlantic, before brushing the Outer Banks of NC

– Then recurved towards the east-northeast over the open Atlantic (Would be categorized as an AR TC)

• No PRE were associated with this TC

– Expansive ridge axis blocked advection of deeper moisture into the U.S.

3838

Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)Track of Gabrielle (Sept. 8-12, 2007)

3939

24 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 200724 Hour QPE –Ending 12z, Sept. 10, 2007

Localized 1-2” (25-50 mm) rainfall amounts in a 24 hour period – Available

moisture was not associated with Gabrielle

4040

Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07Water Vapor – 09z, 9/09/07

Gabrielle

Dry Wedge

Frontal Plume of Moisture…Disconnected from Gabrielle

MSLP Isobars and Mean 925-850 mb Winds

4141

300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07300 mb Analysis – 12z, 9/09/07

L

Gabrielle

Trough Axis

Ridge Axis

4242

850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07850 mb Moisture Transport – 12z, 9/09/07

L

Gabrielle

Axis of minimum Theta-e

4343

Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07Surface Analysis + Radar - 12z, 9/09/07

Ridge axis blocks inflow of moisture towards poleward front

4444

ML Streamlines

Representative TC Tracks

TC Rainfall

PREs

LL θe-Ridge Axis

See inset

UL Jet

Conceptual Model: LOT PRE (SR/AR TC)Conceptual Model: LOT PRE (SR/AR TC)

Revised and updated from Fig. 13 of Bosart and Carr (1978)

4545

ML Streamlines

TC Tracks

TC Rainfall

PREs

LL θe-Ridge Axis

UL Jet

UL Jet

LL θe-Ridge Axis

PREs

Mountain Axes

Idealized LL Winds

LL Temp/ Moisture Boundary

Conceptual Model (More Detailed Inset)Conceptual Model (More Detailed Inset)

4646

Summary – Forecast ChallengesSummary – Forecast ChallengesSummary – Forecast ChallengesSummary – Forecast Challenges

• NWP models are often poor with the placement / intensity of PRE

• Attention is frequently diverted away from potential PRE development

• PRE can impact almost any area of the CONUS

• NWP models are often poor with the placement / intensity of PRE

• Attention is frequently diverted away from potential PRE development

• PRE can impact almost any area of the CONUS

4747

Summary – PRE StatisticsSummary – PRE StatisticsSummary – PRE StatisticsSummary – PRE Statistics

• About 1/3 of U.S. Landfalling TC in our period of study (1998-2006) were PPTC

• LOT PRE were the most common

– Typically the best synoptic enhancement

• AT PRE can be the most dangerous

– Double-shot of heavy rainfall

• ROT PRE tended to display the highest rainfall rates

– Typically slower moving PRE, with less synoptic forcing

– Orography perhaps more important

• About 1/3 of U.S. Landfalling TC in our period of study (1998-2006) were PPTC

• LOT PRE were the most common

– Typically the best synoptic enhancement

• AT PRE can be the most dangerous

– Double-shot of heavy rainfall

• ROT PRE tended to display the highest rainfall rates

– Typically slower moving PRE, with less synoptic forcing

– Orography perhaps more important

4848

Summary – Similarity of TC TracksSummary – Similarity of TC TracksSummary – Similarity of TC TracksSummary – Similarity of TC Tracks

• SR TC had the highest percentage of PPTC

• AR TC were the most common in our period of study

– However, had a lower percentage of PPTC

• CG TC had the lowest percentage of PPTC

– However, CG PPTC were the most prolific PRE producers (an average of 3-4 PRE per TC)

• SR TC had the highest percentage of PPTC

• AR TC were the most common in our period of study

– However, had a lower percentage of PPTC

• CG TC had the lowest percentage of PPTC

– However, CG PPTC were the most prolific PRE producers (an average of 3-4 PRE per TC)

4949

Summary – Favored PRE LocationsSummary – Favored PRE LocationsSummary – Favored PRE LocationsSummary – Favored PRE Locations

• Within the RRQ of a strengthening poleward upper-level jet streak

• Downstream of a mid-level trough, which is well west of the parent TC’s longitude

• Near a low-level boundary

• On the northern or western fringes of a deep tropical moisture plume (evident on water vapor imagery)

• Near or just west of a low-level theta-e ridge axis

• Within the RRQ of a strengthening poleward upper-level jet streak

• Downstream of a mid-level trough, which is well west of the parent TC’s longitude

• Near a low-level boundary

• On the northern or western fringes of a deep tropical moisture plume (evident on water vapor imagery)

• Near or just west of a low-level theta-e ridge axis

5050

Summary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRESummary – Unfavorable Setup for PRE

• A de-amplified, zonally oriented flow pattern is in place north of the TC

• The main poleward mid-level trough axis is already at, or east of the TC’s longitude

• A low-level blocking ridge is north / northeast of the TC

• A de-amplified, zonally oriented flow pattern is in place north of the TC

• The main poleward mid-level trough axis is already at, or east of the TC’s longitude

• A low-level blocking ridge is north / northeast of the TC

5151

Future WorkFuture WorkFuture WorkFuture Work

• Expand PRE database to include the western U.S. (Pacific Basin TC)

• Add composites / conceptual models for AT and ROT PRE, and possibly other TC tracks (i.e. CG)

• Develop a technique to identify / quantify PRE rainfall in TC precipitation analyses

• Perform modeling studies to interrogate the role that TC have in modulating the strength of poleward jets

• Expand PRE database to include the western U.S. (Pacific Basin TC)

• Add composites / conceptual models for AT and ROT PRE, and possibly other TC tracks (i.e. CG)

• Develop a technique to identify / quantify PRE rainfall in TC precipitation analyses

• Perform modeling studies to interrogate the role that TC have in modulating the strength of poleward jets

5252

ReferencesReferencesReferencesReferences• Atallah, E. H., and L. F. Bosart, 2003: The extratropical transition and precipitation distribution of

Hurricane Floyd (1999). Mon. Wea. Rev., 131, 1063–1081.

• Atallah, E., L. F. Bosart, and A. R. Aiyyer, 2007: Precipitation distribution associated with landfalling tropical cyclones over the eastern United States. Mon. Wea. Rev., 135, 2185–2206.

• Bosart and F. H. Carr, 1978: A case study of excessive rainfall centered around Wellsville, New York, 20-21 June 1972. Mon. Wea. Rev., 106, 348–362.

• Bosart and D. B. Dean, 1991: The Agnes rainstorm of June 1972: Surface feature evolution culminating in inland storm redevelopment. Wea. and Forecasting, 6, 515–537.

• Brooks, H. E., and D. J. Stensrud, 2000: Climatology of heavy rain events in the United States from hourly precipitation observations. Mon. Wea. Rev., 128, 1194–1201.

• DeLuca, D. P., 2004: The distribution of precipitation over the Northeast accompanying landfalling and transitioning tropical cyclones. M.S. thesis, Department of Earth and Atmospheric Sciences, University at Albany, State University of New York, 177 pp.

• DiMego, G. J., and L. F. Bosart, 1982a: The transformation of tropical storm Agnes into an extratropical cyclone. Part I: The observed fields and vertical motion computations. Mon. Wea. Rev., 110, 385–411.

• LaPenta, K. D., and Coauthors, 1995: The challenge of forecasting heavy rain and flooding throughout the eastern region of the National Weather Service. Part I: Characteristics and events. Wea. Forecasting, 10, 78–90.

• Schumacher, R. S., and R. H. Johnson, 2005: Organization and environmental properties of extreme-rain-producing mesoscale convective systems. Mon. Wea. Rev., 133, 961–976.

• Uccellini, L. W., and D. R. Johnson, 1979: The coupling of upper and lower tropospheric jet streaks and implications for the development of severe convective storms. Mon. Wea. Rev., 107, 682–703.

• Ulbrich, C. W., and L. G. Lee, 2002: Rainfall characteristics associated with the remnants of tropical storm Helene in upstate South Carolina. Wea. Forecasting, 17, 1257–1267.

• Atallah, E. H., and L. F. Bosart, 2003: The extratropical transition and precipitation distribution of Hurricane Floyd (1999). Mon. Wea. Rev., 131, 1063–1081.

• Atallah, E., L. F. Bosart, and A. R. Aiyyer, 2007: Precipitation distribution associated with landfalling tropical cyclones over the eastern United States. Mon. Wea. Rev., 135, 2185–2206.

• Bosart and F. H. Carr, 1978: A case study of excessive rainfall centered around Wellsville, New York, 20-21 June 1972. Mon. Wea. Rev., 106, 348–362.

• Bosart and D. B. Dean, 1991: The Agnes rainstorm of June 1972: Surface feature evolution culminating in inland storm redevelopment. Wea. and Forecasting, 6, 515–537.

• Brooks, H. E., and D. J. Stensrud, 2000: Climatology of heavy rain events in the United States from hourly precipitation observations. Mon. Wea. Rev., 128, 1194–1201.

• DeLuca, D. P., 2004: The distribution of precipitation over the Northeast accompanying landfalling and transitioning tropical cyclones. M.S. thesis, Department of Earth and Atmospheric Sciences, University at Albany, State University of New York, 177 pp.

• DiMego, G. J., and L. F. Bosart, 1982a: The transformation of tropical storm Agnes into an extratropical cyclone. Part I: The observed fields and vertical motion computations. Mon. Wea. Rev., 110, 385–411.

• LaPenta, K. D., and Coauthors, 1995: The challenge of forecasting heavy rain and flooding throughout the eastern region of the National Weather Service. Part I: Characteristics and events. Wea. Forecasting, 10, 78–90.

• Schumacher, R. S., and R. H. Johnson, 2005: Organization and environmental properties of extreme-rain-producing mesoscale convective systems. Mon. Wea. Rev., 133, 961–976.

• Uccellini, L. W., and D. R. Johnson, 1979: The coupling of upper and lower tropospheric jet streaks and implications for the development of severe convective storms. Mon. Wea. Rev., 107, 682–703.

• Ulbrich, C. W., and L. G. Lee, 2002: Rainfall characteristics associated with the remnants of tropical storm Helene in upstate South Carolina. Wea. Forecasting, 17, 1257–1267.

5353

Any Questions ??Any Questions ??Any Questions ??Any Questions ??

Thank You !!Thank You !!

5454

WFO BGM Usage of HPC ProductsWFO BGM Usage of HPC ProductsWFO BGM Usage of HPC ProductsWFO BGM Usage of HPC Products

• Days 4-7 Gridded Output (Medium Range)

– Common starting point

– HPC has access to more model data / better ensembling capabilities (“Master Blender”)

• Preferable to always populating with one model (GMOS grids)

– Lets us focus on short-term issues

• Days 4-7 Gridded Output (Medium Range)

– Common starting point

– HPC has access to more model data / better ensembling capabilities (“Master Blender”)

• Preferable to always populating with one model (GMOS grids)

– Lets us focus on short-term issues

5555

Usage of HPC Stuff (Shorter Range)Usage of HPC Stuff (Shorter Range)Usage of HPC Stuff (Shorter Range)Usage of HPC Stuff (Shorter Range)

• Model diagnostics

– Will view discussions / graphics in more complicated scenarios

• Especially when there’s significant model discrepancies

• QPF / Excessive Rainfall

– Will often use HPC QPF, or a blend of HPC and other model QPF’s in the first 24 – 48 hours

• Depending on timing, may use data from a previous model cycle

– Will utilize Excessive Rainfall discussions / graphics as guidance in heavy precipitation situations

• Winter Weather Desk

– Will typically view WWD graphics as a “reality check” against our thinking

• Particularly with mixed phase events / model disagreements

• Model diagnostics

– Will view discussions / graphics in more complicated scenarios

• Especially when there’s significant model discrepancies

• QPF / Excessive Rainfall

– Will often use HPC QPF, or a blend of HPC and other model QPF’s in the first 24 – 48 hours

• Depending on timing, may use data from a previous model cycle

– Will utilize Excessive Rainfall discussions / graphics as guidance in heavy precipitation situations

• Winter Weather Desk

– Will typically view WWD graphics as a “reality check” against our thinking

• Particularly with mixed phase events / model disagreements

matthew cote, lance bosart, and daniel keyser state university of new york, albany, ny

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