Flash Flood Monitoring and Prediction (FFMP)

Flash FloodMonitoring and Prediction

(FFMP)

Flash FloodMonitoring and Prediction

(FFMP)

John Ferree

Warning Decision Training Branch

Norman, OK

John Ferree

Warning Decision Training Branch

Norman, OK

Severe Weather/Flash Flood WDM

September 10-13, 2002

Quote Quote

“Merely because technology plays a very important part in war, it does not follow that it alone can dictate the conduct of a war or lead to victory.”

-Martin van Creval Noted Military

Historian

“Merely because technology plays a very important part in war, it does not follow that it alone can dictate the conduct of a war or lead to victory.”

-Martin van Creval Noted Military

Historian

OverviewOverview

• FFMP – How?, What?, When?, and Why?

• FFMP 2.0 Products

• FFMP 2.0 Limitations and Operational Use

• FFMP – How?, What?, When?, and Why?

• FFMP 2.0 Products

• FFMP 2.0 Limitations and Operational Use

WARN

DON'TWARN

Flash Flood Lead TimesFlash Flood Lead Times

0

10

20

30

40

50

60

1990 1995 2000 2005 2010

Year

Lea

d-T

ime,

Min

ute

s

Actual Goal

GPRA Informationhttp://205.156.54.206/ost/nws_sci_needs_final_02_20_02.pdf

http://205.156.54.206/ost/nws_sci_needs_final_02_20_02.pdf








Flash Flood Accuracy (POD)Flash Flood Accuracy (POD)

GPRA Informationhttp://205.156.54.206/ost/nws_sci_needs_final_02_20_02.pdf

40

50

60

70

80

90

100

1990 1995 2000 2005 2010

Year

FF

Acc

ura

cy (

PO

D),

Per

cen

t

Actual Goal









PBZ Flash Flood VerificationPBZ Flash Flood Verification

• Flash Flood Monitoring and Prediction (FFMP) algorithm is based on the Areal Mean Basin Estimated Rainfall (AMBER)

– Bob Davis

• Pittsburgh, PA WFO

– Paul Jendrowski

• Blackburg, VA WFO

• Flash Flood Monitoring and Prediction (FFMP) algorithm is based on the Areal Mean Basin Estimated Rainfall (AMBER)

– Bob Davis

• Pittsburgh, PA WFO

– Paul Jendrowski

• Blackburg, VA WFO

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1990 1992 1994 1996 1998 2000

POD

FAR

CSI

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1990 1992 1994 1996 1998 2000

POD

FAR

CSI

AMBER operational since May 1996

FFMP Overview FFMP Overview

• Continuous monitoring of rainfall rate and its comparison to flash flood guidance (FFG) for high resolution stream basins.

• Automated alerts when a dangerous flood situation may be developing on a given stream or catchment.

• Continuous monitoring of rainfall rate and its comparison to flash flood guidance (FFG) for high resolution stream basins.

• Automated alerts when a dangerous flood situation may be developing on a given stream or catchment.

Flash Flood Monitoring and Prediction In AWIPS Build 5 and Beyond

- Smith et al 2000, Preprints 15th Conference on Hydrology, AMS



FFMP BenefitsFFMP Benefits

• Longer lead times

• Fewer missed events

• Increased forecaster situational awareness

• Reduced forecaster fatigue

• Focus for applied research

• Longer lead times

• Fewer missed events

• Increased forecaster situational awareness

• Reduced forecaster fatigue

• Focus for applied researchFlash Flood Monitoring and Prediction In AWIPS Build 5 and Beyond




FFMP 2.0 BasicsFFMP 2.0 Basics

• AWIPS build 5.1.2 - using WSR-88D Digital Hybrid Scan Reflectivity (DHR)

• All basins (>2 mi2) in county warning area are pre-defined

• Basin rainfall rate (in/hr) is computed from the DHR on a basin level every volume scan

• Accumulations (of various time scales) are compared to Flash Flood Guidance (FFG) on a county and basin scale

• AWIPS build 5.1.2 - using WSR-88D Digital Hybrid Scan Reflectivity (DHR)

• All basins (>2 mi2) in county warning area are pre-defined

• Basin rainfall rate (in/hr) is computed from the DHR on a basin level every volume scan

• Accumulations (of various time scales) are compared to Flash Flood Guidance (FFG) on a county and basin scale

FFMP InputsDHR and FFGFFMP InputsDHR and FFG

• Digital Hybrid Reflectivity (DHR)

– 1 km (.54nm) x 1 degree

– 256 data levels

– 124 nm range

– Nearest 0.5 dBZ

• FFMP processorconverts to rainfall rate

• Digital Hybrid Reflectivity (DHR)

– 1 km (.54nm) x 1 degree

– 256 data levels

– 124 nm range

– Nearest 0.5 dBZ

• FFMP processorconverts to rainfall rate

FFMP InputsDHR and FFGFFMP InputsDHR and FFG

• RFC provided flash flood guidance (FFG) on the basin rainfall accumulations over a specific time period (1, 3, and 6 hours) needed to initiate flooding on streams.

• Assumes no rainfall since data cutoff.

• RFC provided flash flood guidance (FFG) on the basin rainfall accumulations over a specific time period (1, 3, and 6 hours) needed to initiate flooding on streams.

• Assumes no rainfall since data cutoff.

Flash Flood Guidance (FFG)Limitations

Flash Flood Guidance (FFG)Limitations

• Only provides average values for large areas.

• Does not truly account for the effects of intensity.

• Utilizes forecast models not specifically calibrated for flash flood events.

• Capable of producing satisfactory results in areas where soil moisture is key factor (East , Central and South), but not in the arid west.

• Procedures can be difficult to maintain/update.

• Only provides average values for large areas.

• Does not truly account for the effects of intensity.

• Utilizes forecast models not specifically calibrated for flash flood events.

• Capable of producing satisfactory results in areas where soil moisture is key factor (East , Central and South), but not in the arid west.

• Procedures can be difficult to maintain/update.

Courtesy Bob Cox - MBRFC

Resolution of Gridded Threshold Runoff Values

Resolution of Gridded Threshold Runoff Values


Resolution ofRainfall-Runoff Curves

Resolution ofRainfall-Runoff Curves


Resolution of FFMP BasinsResolution of FFMP Basins


Uniform FFG ValuesUniform FFG Values


Non-Uniform Rainfall EventNon-Uniform Rainfall Event


“True” Gridded FFG Values“True” Gridded FFG Values


New “Gridded” FFG Values Issued by RFC

New “Gridded” FFG Values Issued by RFC


Repeat Rainfall Over Same AreaRepeat Rainfall Over Same Area


Repeat Rainfall Over Different Area

Repeat Rainfall Over Different Area


Efforts to Improve FFGEfforts to Improve FFG

• Flash Flood Improvement Team (FFIT)

– Mission: Develop a plan to modify or develop hydrologically sound, national flash flood guidance procedures. The plan will contain realistic recommendations to improve flash flood guidance in the short term (1-2 years).

• Verification of FFG

• WR GIS-based approach to flash flood potential

• Distributed Modeling - RFCs and WFOs(??)

• Flash Flood Improvement Team (FFIT)

– Mission: Develop a plan to modify or develop hydrologically sound, national flash flood guidance procedures. The plan will contain realistic recommendations to improve flash flood guidance in the short term (1-2 years).

• Verification of FFG

• WR GIS-based approach to flash flood potential

• Distributed Modeling - RFCs and WFOs(??)


FFMP OutputsFFMP Outputs

• Graphic displays of:

– Basin rainfall accumulation

– Ratio of basin accumulations to FFG

– Accumulations – FFG (Difference)

– For time periods of from 30 minutes to 6 hours

• Line graph of basin rainfall, basin rainfall rate, and FFG for the same time periods.

• Graphic displays of:

– Basin rainfall accumulation

– Ratio of basin accumulations to FFG

– Accumulations – FFG (Difference)

– For time periods of from 30 minutes to 6 hours

• Line graph of basin rainfall, basin rainfall rate, and FFG for the same time periods.

County Level Display of Basin Average Precipitation

County Level Display of Basin Average Precipitation

• Display of the One Hour Basin Average Precipitation of the Basin in the County that has the highest precipitation total.

• Display of the One Hour Basin Average Precipitation of the Basin in the County that has the highest precipitation total.

Basin Average PrecipitationBasin Average Precipitation

• Display of Basin level precipitation will only display those basins within the county selected.

• Display of Basin level precipitation will only display those basins within the county selected.

County Precip. / FFG RatioCounty Precip. / FFG Ratio

• County level ratio values are calculated using the maximum basin precipitation in the county, divided by the county average FFG.

• County level ratio values are calculated using the maximum basin precipitation in the county, divided by the county average FFG.

Basin Precip. / FFG RatioBasin Precip. / FFG Ratio

• Basin level ratio of precipitation accumulations divided by basin level FFG.

• Basin level ratio of precipitation accumulations divided by basin level FFG.

County Precip – FFG (Diff)County Precip – FFG (Diff)

• County level difference values are calculated using the maximum basin precipitation in the county minus the county average FFG.

• County level difference values are calculated using the maximum basin precipitation in the county minus the county average FFG.

Basin Precip. - FFG (Diff)Basin Precip. - FFG (Diff)

• Basin level 1 hour precipitation minus FFG

• Note table duration is set at 1 hour, but graphic states 1.5 hour.What happened here?

• Basin level 1 hour precipitation minus FFG

• Note table duration is set at 1 hour, but graphic states 1.5 hour.What happened here?

What’s Better?What’s Better?

Ratio Difference

FFMP Flash Flood AnalysisFFMP Flash Flood Analysis

Basin Trend Graph takes some getting used to. Where the accumulation (colored area) exceeds the FFG (purple line) there is a threat of flash flooding.

Basin Trend Graph takes some getting used to. Where the accumulation (colored area) exceeds the FFG (purple line) there is a threat of flash flooding.

Flash Flood Threat Index (FFTI)Flash Flood Threat Index (FFTI)

• The color of the FFTI will represent the value of the chosen attribute over a chosen time period

– Basin Accumulation

– Ratio of accumulation to FFG

– Difference between accumulation and FFG

– Time Frame from 30 minutes to six hours

• The color of the FFTI will represent the value of the chosen attribute over a chosen time period

– Basin Accumulation

– Ratio of accumulation to FFG

– Difference between accumulation and FFG

– Time Frame from 30 minutes to six hours

Flash Flood Threat Index (FFTI)Flash Flood Threat Index (FFTI)

• White - Little or no activity

• Green - Precipitation

• Yellow - Moderate precipitation

• Red - Heavy precipitation

• Grey - Not functioning properly

• White - Little or no activity

• Green - Precipitation

• Yellow - Moderate precipitation

• Red - Heavy precipitation

• Grey - Not functioning properly

FFTI Change GUI – left click on “FF” button

FFMP LimitationsFFMP Limitations

• Delineated basins require customization

• Mapping of basin to DHR critical to output

• Requires knowledge of basins and stream flow from basin to basin

• Radar limitations are masked

• Flash Flood Guidance development processes inconsistent from RFC to RFC






FFMP 2.0 Basin DelineationFFMP 2.0 Basin Delineation

• National Basin Delineation Project

– NSSL

• ArcInfo used to define the watershed boundaries

• USGS 1 arc second (30 m) DEM data supplied by EROS Data Center

• Continental U.S. completed June 2002.

• National Basin Delineation Project

– NSSL

• ArcInfo used to define the watershed boundaries

• USGS 1 arc second (30 m) DEM data supplied by EROS Data Center

• Continental U.S. completed June 2002.

www.nssl.noaa.gov/teams/western/basinswww.nssl.noaa.gov/teams/western/basins

FFMP 2.0 Basin DelineationFFMP 2.0 Basin Delineation

• Basin Customization

– COMET

– 3-day course

– Skills to identify, create, alter, and re-define high resolution basins delineated by NSSL

– GIS skills and tools

• Basin Customization

– COMET

– 3-day course

– Skills to identify, create, alter, and re-define high resolution basins delineated by NSSL

– GIS skills and tools

http://www.comet.ucar.edu/class/basin_customization/index.htmhttp://www.comet.ucar.edu/class/basin_customization/index.htm

2130 – 2135 UTC Rainfall (in/hr)

.41

.38

.39 .37

.29 .14

.20

.30.16

.24

Grid size 1o x 1km

Conversion Rainfall Rate to Basin Rainfall Rate


Watershed

Boundary


.29

.29

.29 .29

.29

.29

.29.29

.29

Grid size 1o x 1km



Watershed

Boundary

.29


.41

.38

.39 .37

.29 .14

.20

.30.16

.24



If watershed is divided into segments


.37

.37

.37 .25

.25 .25

.25

.37.20

.20



Large Variation in Rainfall Rate in Short Distance

Basin to Basin FlowBasin to Basin Flow

Flash Flood forecasting requires more than accurate forecasts of excessive accumulation.

Flash Flood forecasting requires more than accurate forecasts of excessive accumulation.

Know your basins!

Basin Average RainfallBasin Average Rainfall

• Basin may include

– Several 1 km (.54nm) x 1 degree bins

– One 1 km (.54nm) x 1 degree bin

• Height of reflectivity used for calculation may be

– Hundreds of feet

– Over 10,000 feet

• Basin may include

– Several 1 km (.54nm) x 1 degree bins

– One 1 km (.54nm) x 1 degree bin

• Height of reflectivity used for calculation may be

– Hundreds of feet

– Over 10,000 feet

0

0.5

1

1.5

2

2.5

3

3.5

4

0 50 100 150 200

Radar Range (km)

DH

R G

rid

Siz

e (k

m2)

0

0.5

1

1.5

2

2.5

3

3.5

4

0 50 100 150 200

Radar Range (km)

DH

R G

rid

Siz

e (k

m2)

DHR Grid Area vs. Radar RangeDHR Grid Area vs. Radar RangeDHR Grid Area vs. Radar RangeDHR Grid Area vs. Radar Range

Radar Precipitation EstimatesRadar Precipitation Estimates

• Recall limitations of radar precipitation estimates

– Brightband contamination

– Hail contamination

– Inaccurate Z/R relationship

• Recall limitations of radar precipitation estimates

– Brightband contamination

– Hail contamination

– Inaccurate Z/R relationship

More difficult to identify bright More difficult to identify bright band on FFMP than on band on FFMP than on precipitation productsprecipitation products

More difficult to identify bright More difficult to identify bright band on FFMP than on band on FFMP than on precipitation productsprecipitation products

SummarySummary

• Flash Flood forecasting requires more than accurate forecasts of excessive accumulation.

– Know your basins!

• Radar estimates of rainfall accumulations may be inaccurate.

– Keep radar limitations in mind!

• Flash Flood Guidance does not take into account rainfall and associated soil saturation since data cutoff time.

• Flash Flood forecasting requires more than accurate forecasts of excessive accumulation.

– Know your basins!

• Radar estimates of rainfall accumulations may be inaccurate.

– Keep radar limitations in mind!

• Flash Flood Guidance does not take into account rainfall and associated soil saturation since data cutoff time.

Questions or Comments? Questions or Comments?

• [email protected]

• www.wdtb.noaa.gov

• 405-366-6560 ext 4266

• [email protected]

• www.wdtb.noaa.gov

• 405-366-6560 ext 4266

Flash Flood Monitoring and Prediction (FFMP)

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