american meteorological society - january 15, 2009 national weather service river flood warning...

American Meteorological Society - January 15, 2009

National Weather Service National Weather Service

River Flood Warning River Flood Warning

Verification Verification Mary Mullusky, Ernest Wells, Timothy Helble, Mary Mullusky, Ernest Wells, Timothy Helble,

and Thomas Grazianoand Thomas Graziano

Hydrologic Services DivisionHydrologic Services DivisionOffice of Climate, Water, and Weather ServicesOffice of Climate, Water, and Weather Services

National Weather Service National Weather Service

2American Meteorological Society - January 15, 2009

Floods versus Flash FloodsFloods versus Flash Floods

• Flash Flood

– Quick responding streams (reach flood stage in < 6 hrs after the heavy rain started)

– Warnings issued for defined areas based on hydrometeorological criteria and observer reports

• River Flood– River rises to flood stage over

many hours or days (> 6 hrs)– Longer lasting events– Based on forecasts for specific

gaged locations, prepared by NWS hydrologists


NWS River Flood Warning VerificationNWS River Flood Warning VerificationBackgroundBackground

The NWS issues river forecasts, watches and warnings for over 4000 locations nationwide.


Flood Watch versus River Flood Flood Watch versus River Flood WarningWarning

• Flood Watch– Conditions are favorable

for flooding but flooding is not imminent or occurring

– Not verified

• River Flood Warning – Issued for any high flow,

overflow, or inundation event which is threatening lives and property and can be quantified or indexed at specific river locations

– Verified

WGUS42 KMHX 061600FLWMHX

BULLETIN - IMMEDIATE BROADCAST REQUESTED FLOOD WARNINGNATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC1200 PM EDT FRI APR 6 2012

...THE NATIONAL WEATHER SERVICE IN NEWPORT HAS ISSUED A FLOOD WARNING FOR THE FOLLOWING RIVER IN NORTH CAROLINA...

NEUSE RIVER AT KINSTON AFFECTING CRAVEN AND LENOIR COUNTIES.

.HEAVY RAINFALL TOMORROW WILL CAUSE THE NEUSE RIVER TO RISE NEAR OR ABOVE FLOOD STAGE.

SAFETY MESSAGE...NEVER DRIVE CARS...TRUCKS OR SPORT UTILITY VEHICLES THROUGH FLOODED AREAS.

NCC049-107-070200-/O.NEW.KMHX.FL.W.0001.120407T1300Z-000000T0000Z//KINN7.1.ER.120407T1300Z.120412T0100Z.000000T0000Z.NO/1200 PM EDT FRI APR 6 2012

THE NATIONAL WEATHER SERVICE IN NEWPORT HAS ISSUED A

* FLOOD WARNING FOR THE NEUSE RIVER AT KINSTON.* FROM SATURDAY MORNING UNTIL FURTHER NOTICE.* AT 900 AM EDT FRIDAY THE STAGE WAS 13.5 FEET.* MINOR FLOODING IS FORECAST.* FLOOD STAGE IS 14.0 FEET.* FORECAST...FLOOD STAGE WILL BE REACHED AT 900 AM SATURDAY. MAXIMUM STAGE WILL BE 15.0 FEET AT 900 PM EDT WEDNESDAY. THE RIVER MAY REMAIN ABOVE FLOOD STAGE FOR SEVERAL WEEKS.* IMPACT...AT 14 FEET...WATER WILL BEGIN TO OVERFLOW INTO LOWLANDS ADJACENT TO THE NEUSE RIVER.

$$


NWS River Flood Warning VerificationNWS River Flood Warning VerificationObjectiveObjective

• Objective: To provide national metrics of river flood warning lead

time and accuracy similar to flash flood metrics– Hydrology Program committed to providing national metrics of river flood warning

lead time and accuracy in both PPBES and OMB PART

– The implementation of VTEC/HVTEC provided the data necessary to create a single

source river flood warning verification system

– OCWWS HSD and Regions coordinated on the requirements for the river flood

warning verification system in Q2 FY08

– The OCWWS Performance and Awareness Branch began archiving all FLW’s (and

all other products with the same WMO header) since October 1, 2007.

– The OCWWS Performance and Awareness Branch delivered a prototype system

September 2008


• Metrics– Probability of Detection

– False Alarm Ratio

– Critical Success Index

– Lead Time

– Absolute Timing Error

• Metric Stratification– by Time (day, multiple days, month, multiple months, year)

– by location (point, groupings of points, WFO, RFC, Region, National)

– by Typical River Response (slow, medium, fast)

NWS River Flood Warning VerificationNWS River Flood Warning VerificationMetrics and System RequirementsMetrics and System Requirements


Product Information UsedProduct Information Used

• 1st Product Issuance– NWS location identifier, VTEC action code (NEW), product issuance

time, rise above time (forecast)

• Last Product Issuance

– NWS location identifier, VTEC action code (CAN,EXP), product issuance time, rise above time (observation), fall below time (observation)

NCC049-107-070200-/O.NEW.KMHX.FL.W.0001.120407T1300Z-000000T0000Z//KINN7.1.ER.120407T1300Z.120412T0100Z.000000T0000Z.NO/1200 PM EDT FRI APR 6 2012

Issuances Used:

Hydrologic VTEC used:


NWS River Flood Warning VerificationNWS River Flood Warning VerificationLogic TreeLogic Tree

Is the last product action codeequal to ‘CAN’ or ‘EXP’

or Is the last product PVTEC End time +120 hours

EARLIER than the current time?

1 Unwarned Event (e.g., missed event)

LT=0, ATE not calculated

1 Unknown Event Do NOT use in verification statistics

1 Warned Event (e.g., hit)LT = last product Rise Above time – 1st

Product Issuance TimeATE = |last product Rise Above time-1st Product Rise Above Time|

Is the Last product Rise AboveTime And Crest Time and Fall Below

Time Equal to a string of zeros and

Is the action code equal to ‘CAN’?

YES NO

Is the Last productRise Above Time EARLIER than the

last product issuance time?

YESNO

YESNO

YES

Event Not OverDo NOT USE in official statsNO

Is the 1st product Issuance Time EARLIER than or Equal to

the last product Rise Above Time?

1 Incorrectly Warned Event (e.g., false alarm)

LT and ATE not calculated

1 Incorrectly Warned Event (e.g., false alarm)

LT and ATE not calculated

1 Unwarned Event (e.g., missed event)

LT=0, ATE not calculated

1 Unknown Event Do NOT use in verification statistics

Event Not OverDo NOT USE in official stats

1 Warned Event (e.g., hit)LT = last product Rise Above time – 1st

Product Issuance TimeATE = |last product Rise Above time-1st Product Rise Above Time|


• Observations Issues

– Quality Control of Observations - same level of WHFS QC applied prior to

product issuance. Some QC automated with data ingest.

– No Observation – event not included in metric

– Reporting Frequency - system captures verification statistics for all locations

where observations are available. However, we will only report statistics for

those sites where the observational frequency is sufficient to assure the

integrity of the verification data.

• Underestimates missed events.

• Prototype is still being tested – errors are likely

• Database incomplete – Currently only includes points that have river

response classification and are in the HADS database

NWS River Flood Warning VerificationNWS River Flood Warning VerificationLimitationsLimitations


NWS River Flood Warning VerificationNWS River Flood Warning VerificationWY2008 Preliminary ResultsWY2008 Preliminary Results

All River Response

0

0.2

0.4

0.6

0.8

1

National Central Eastern Southern Western

POD FAR

2435 1160 435 798

42

# of events

Medium River Response

0

0.2

0.4

0.6

0.8

1


POD FAR

891 400 201 27317

# of events

Fast River Response

0

0.2

0.4

0.6

0.8

1


POD FAR

945 390 173 365

17

# of events

Slow River Response

0

0.2

0.4

0.6

0.8

1


POD FAR

599

370

61 160 8

# of events


NWS River Flood Warning VerificationNWS River Flood Warning VerificationFY2008 Preliminary ResultsFY2008 Preliminary Results

All River Response

0

5

10

15

20

25


Ho

urs

Average Leadtime Average Abs. Timing Errror

1447 708

283

42432

# of hits

Slow River Response

0

10

20

30

40

50


Ho

urs


382 239 43

946

Medium River Response

0

5

10

15


Ho

urs


545 257 126 151 11

# of hits

Fast River Response

05

101520253035


Ho

urs


520212

114

17915

# of hits


NWS River Flood Warning VerificationNWS River Flood Warning VerificationNext StepsNext Steps

• Expand Interface to get detailed reports of events

• Expand database - Each flood warning location

must have a classified river response and an

observation reporting frequency

• Rigorous Testing

• Develop River Flood Warning Lead Time and

Accuracy performance goals

American Meteorological Society - January 15, 2009

Any Questions?Any Questions?

american meteorological society - january 15, 2009 national weather service river flood warning...

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