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 Mary Mullusky, Ernest Wells, Timothy Helble, and Thomas Graziano Helble, and Thomas Graziano Hydrologic Services Division Hydrologic Services Division Office of Climate, Water, and Weather Office of Climate, Water, and Weather Services Services National Weather Service National Weather Service
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American Meteorological Society - January 15, 2009 National Weather Service River Flood Warning Verification Mary Mullusky, Ernest Wells, Timothy Helble,
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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
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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
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NWS River Flood Warning VerificationNWS River Flood Warning VerificationBackgroundBackground
The NWS issues river forecasts, watches and warnings for over 4000 locations nationwide.
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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.
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.
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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
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• 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
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