1. 1 AMBER Areal Mean Basin Estimated Rainfall COMAP Flash Flood Course Robert S. Davis, Pittsburgh WFO

2. 2 AMBER Overview AMBER Overview All watersheds in county warning area are defined to a Minimum Basin Area (MBA) of 2 mi 2 to show spatial rainfall distribution.All watersheds in county warning area are defined to a Minimum Basin Area (MBA) of 2 mi 2 to show spatial rainfall distribution. The WSR-88D polar grid (1 o by 1 km) is mapped to the defined watersheds.The WSR-88D polar grid (1 o by 1 km) is mapped to the defined watersheds. Average Basin Rainfall (ABR) is computed for each watershed every volume scan.Average Basin Rainfall (ABR) is computed for each watershed every volume scan. An hourly ABR rate is determined from the single volume scan (5-6 min.) of ABR.An hourly ABR rate is determined from the single volume scan (5-6 min.) of ABR.

3. 3 Digital Radar Rainfall

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5. 5 Digital Radar Data Radar provides 3 rainfall measurements, location, time, and quantitative estimate.Radar provides 3 rainfall measurements, location, time, and quantitative estimate. Radar grid size determines the minimum basin area (MBA) for ABR computations.Radar grid size determines the minimum basin area (MBA) for ABR computations. Sample rate determines time interval, but product time interval may be larger.Sample rate determines time interval, but product time interval may be larger. Z/R relationship determines rainfall estimate. (Sources of error important!!)Z/R relationship determines rainfall estimate. (Sources of error important!!)

6. 6 Digital Rainfall Products Manually Digitized RadarManually Digitized Radar (MDR:1975-1993) 40 km grid / 1 hour RADAP-II digital rainfall (1977-1993)RADAP-II digital rainfall (1977-1993) 10-12 offices. Polar grid (2 o x 2.2 km / 10 min.) WSR-88D Digital Precipitation ArrayWSR-88D Digital Precipitation Array (DPA:1993-current) 4 km grid - 1 hour WSR-88D Digital Hybrid Scan ReflectivityWSR-88D Digital Hybrid Scan Reflectivity (DHR:1999-current) Polar grid: (1 o x 1 km / 5 min.)

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8. 8 Digital Precipitation Array (DPA) Time interval (1 hour)Time interval (1 hour) Data grid size (HRAP 4 km x 4 km grid)Data grid size (HRAP 4 km x 4 km grid) Rainfall estimates in the WSR-88D polar grid (1 o x 2 km) are averaged to produce a single rainfall estimate in each HRAP grid.Rainfall estimates in the WSR-88D polar grid (1 o x 2 km) are averaged to produce a single rainfall estimate in each HRAP grid. Used for Stage 1-3 precipitation estimation and for FFMP in AWIPS Build 5.0.Used for Stage 1-3 precipitation estimation and for FFMP in AWIPS Build 5.0.

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10. 10 Digital Hybrid Scan Reflectivity (DHR) Time interval (5-6 minutes)Time interval (5-6 minutes) Grid size (1 degree x 1 km)Grid size (1 degree x 1 km) Reflectivity to the nearest 0.5 dBZReflectivity to the nearest 0.5 dBZ

11. 11 AMBER DHR Grid Assignment AMBER DHR Grid Assignment DHR grid is mapped to all defined watershed segments. This allows ABR computation in 5-6 minute time steps.DHR grid is mapped to all defined watershed segments. This allows ABR computation in 5-6 minute time steps. DHR grid is mapped to all urban areas to compute ABR urban rainfall.DHR grid is mapped to all urban areas to compute ABR urban rainfall. Single 1km DHR bins are assigned to location of all rain gages, allowing gage comparison with radar estimated rainfall.Single 1km DHR bins are assigned to location of all rain gages, allowing gage comparison with radar estimated rainfall.

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13. 13 DHR Grid Area (km 2 ) vs. Radar Range (km)

14. 14 Stream Basin Definitions

15. 15 National Basin Delineation 30Sep1999 – NWS agrees to fund the AMBER National Basin Delineation project by NSSL for all of the United States.30Sep1999 – NWS agrees to fund the AMBER National Basin Delineation project by NSSL for all of the United States. ArcInfo used to define the watershed boundaries.ArcInfo used to define the watershed boundaries. USGS 1 arc second (30 m) DEM data supplied by EROS Data Center.USGS 1 arc second (30 m) DEM data supplied by EROS Data Center. www.nssl.noaa.gov/teams/western/basinswww.nssl.noaa.gov/teams/western/basins

16. 16 AMBER Watershed Division All watersheds in the county warning area are divided into hydrologic segments no larger than 10 mi 2.All watersheds in the county warning area are divided into hydrologic segments no larger than 10 mi 2. A Minimum Basin Area of 2 mi 2 is used in the initial NSSL stream creation procedure.A Minimum Basin Area of 2 mi 2 is used in the initial NSSL stream creation procedure. Each forecast office may modify the NSSL stream database (subdivide or aggregate).Each forecast office may modify the NSSL stream database (subdivide or aggregate).

17. 17 ABR and ABR Rate Computations

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19. 19 Flash Flood Threat and ABR Severity of flash flooding is directly related to the observed ABR in a watershed.Severity of flash flooding is directly related to the observed ABR in a watershed. The time period of the ABR determines the ABR rate. The higher the ABR rate, the greater the risk of serious flash flooding.The time period of the ABR determines the ABR rate. The higher the ABR rate, the greater the risk of serious flash flooding. ABR varies as function of watershed area. As watershed area increases, ABR and ABR rate tend to decrease.ABR varies as function of watershed area. As watershed area increases, ABR and ABR rate tend to decrease.

20. 20 ABR Rate Based on 5-6 minute observed ABR.Based on 5-6 minute observed ABR. Hourly ABR Rate = ABR x 3600/vsec, where vsec= the number of seconds in the volume scan.Hourly ABR Rate = ABR x 3600/vsec, where vsec= the number of seconds in the volume scan. ABR Rate is used to identify watersheds currently receiving the heaviest rainfall, before the flash flood producing accumulation occurs.ABR Rate is used to identify watersheds currently receiving the heaviest rainfall, before the flash flood producing accumulation occurs.

21. 21 Pittsburgh Urban Flash Flood May 18, 1999

22. 22 ABR in Watersheds

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24. 24 AMBER Time Display Interval 5-minute ABR: Used to compute ABR Rate and to sum the ABR through a 2 hour time period.5-minute ABR: Used to compute ABR Rate and to sum the ABR through a 2 hour time period. 15-minute ABR: Used for comparison with IFLOWS rain gage data and to sum the ABR through a 6 hour time period.15-minute ABR: Used for comparison with IFLOWS rain gage data and to sum the ABR through a 6 hour time period. 1-hour ABR: Used for history of ABR in a watershed and to sum ABR through a 24 hour time period.1-hour ABR: Used for history of ABR in a watershed and to sum ABR through a 24 hour time period.

25. 25 24 Hour ABR-Rainfall History The history of ABR in a watershed for the past 24 hours can be compared with the MAP rainfall used to update FFG.The history of ABR in a watershed for the past 24 hours can be compared with the MAP rainfall used to update FFG. The AMBER 24 hour ABR product can be used to determine the rainfall distribution in any watershed for the previous 24-72 hours.The AMBER 24 hour ABR product can be used to determine the rainfall distribution in any watershed for the previous 24-72 hours. ABR is displayed in one hour increments with a running 24 hour total.ABR is displayed in one hour increments with a running 24 hour total.

26. 26 Turtle Creek (1) ABR #1108 18 May 1999 1-hour data

27. 27 Turtle Creek (1) ABR #1108 18-19 May 1999 15-minute data

28. 28 Turtle Creek(1) #1108 Turtle Creek Monongahela River Braddock Lock Kenmore Ave. Electric Ave. 5321 5322 6334 6598 6336 6597 6335 6599 6309 6310 6605 6596 Pitcairn 5.09 4.40 4.28 3.76 3.72 3.22 3.09 1.81 2.12 2.46 1.75 X.XX = ABR 18MAY1999 2000 UTC- 19MAY1999 0200 UTC 3.03 (inches) 2.4 2.3 3.8 3.1 2.8 1.8 2.7 0.7 0.5 1.4 0.2 0.9 x.x = Area (square miles)

29. 29 Forest Hills Run ABR #5321 18-19May1999 15 min. data

30. 30 Forest Hills Run ABR #5321 18May1999 5 min. data

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38. 38 Forest Hills EMA Reports 2215 UTC - First reports of water in basements.2215 UTC - First reports of water in basements. 2300 - 0100 UTC many cars stranded along Ardmore Boulevard.2300 - 0100 UTC many cars stranded along Ardmore Boulevard. 0056 UTC - 10/homes/20 people evacuated on Kenmore Avenue.0056 UTC - 10/homes/20 people evacuated on Kenmore Avenue.

39. 39 ABR in Urban Areas NWSFO Localization

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41. 41 Mon Valley Urban Areas Total population 86,565 Rankin/Braddock 8,256 3.0mi 2Rankin/Braddock 8,256 3.0mi 2 Clairton 12,188 1.3mi 2Clairton 12,188 1.3mi 2 McKeesport 31,012 2.0mi 2McKeesport 31,012 2.0mi 2 Glassport 6,242 1.2mi 2Glassport 6,242 1.2mi 2 Port Vue 5,316 0.9mi 2Port Vue 5,316 0.9mi 2 Wilson/Dravosburg 11,075 0.8mi 2Wilson/Dravosburg 11,075 0.8mi 2 Duquesne 10,094 1.4mi 2Duquesne 10,094 1.4mi 2 Liberty 3,112 2.2mi 2Liberty 3,112 2.2mi 2

42. 42 AMBER Rain Gage Computation NWSFO Localization

43. 43 AMBER Z/R Gage Comparison The single 1km DHR bin that contains the rain gage is used to compute the radar rainfall estimate.The single 1km DHR bin that contains the rain gage is used to compute the radar rainfall estimate. Tropical vs. Standard Z/R usage can be estimated using 15 minute gage data.Tropical vs. Standard Z/R usage can be estimated using 15 minute gage data. Gage comparisons should be done to verify validity of the WSR-88D rainfall estimates.Gage comparisons should be done to verify validity of the WSR-88D rainfall estimates.

44. 44 Braddock Lock 2 ABR #4332 18-19May1999 15 min. data 24 hr Gage: 4.44 inches

45. 45 Braddock Lock 2 ABR #4332 18May1999 5 min. data 24 hr Gage: 4.44 inches

46. 46 Amber arrives in AWIPS Build 5.1

47. 47 Flash Flood Monitoring and Prediction (FFMP) in AWIPS Build 5.0: FFMP will compare DPA rainfall with FFG (HRAP 4 km x 4km grid). No ABR computations.Build 5.0: FFMP will compare DPA rainfall with FFG (HRAP 4 km x 4km grid). No ABR computations. Build 5.1 FFMP will compute AMBER ABR and ABR Rate, using the DHR product (1 o x 1 km polar grid) and the NSSL NBD watersheds.Build 5.1 FFMP will compute AMBER ABR and ABR Rate, using the DHR product (1 o x 1 km polar grid) and the NSSL NBD watersheds.

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50. 50 AMBER Both Standard and Tropical Convective Z/R

51. 51 Tropical Z/R Cases Standard Z/R: Z = 300R 1.4Standard Z/R: Z = 300R 1.4 Tropical Z/R: Z = 250R 1.2Tropical Z/R: Z = 250R 1.2 Maximum Rate Cap 5.0 in/hr?Maximum Rate Cap 5.0 in/hr? Tropical Storm not required!!!Tropical Storm not required!!!

52. 52 Conclusions Small watersheds definition is the key to detection of flash flooding.Small watersheds definition is the key to detection of flash flooding. ABR Rate gives early warning for flash flood potential.ABR Rate gives early warning for flash flood potential. Time duration of rainfall (5, 15, 60 minutes) impacts forecaster perception of flash flood threat.Time duration of rainfall (5, 15, 60 minutes) impacts forecaster perception of flash flood threat. User selectable time window needed (30, 60, 90, 120, 150, 180 minutes).User selectable time window needed (30, 60, 90, 120, 150, 180 minutes).

53. 53 AMBER Summary ABR provides basin specific rainfall to determine flash flood risk (ABR-FFG)ABR provides basin specific rainfall to determine flash flood risk (ABR-FFG) ABR rate focuses forecaster attention on critical streams before flooding occurs.ABR rate focuses forecaster attention on critical streams before flooding occurs. History of ABR helpful in adjusting FFG for multiple rainfall events.History of ABR helpful in adjusting FFG for multiple rainfall events. Basin specific ABR allows forecaster to mention “threat area” in warning text.Basin specific ABR allows forecaster to mention “threat area” in warning text.

54. 54 AMBER Data Sources ArcView and the spatial analyst extension. www.esri.comArcView and the spatial analyst extension. www.esri.com USGS Data (3 arc second DEM data) edcwww.cr.usgs.govUSGS Data (3 arc second DEM data) edcwww.cr.usgs.gov EPA Data (RF3 data files) www.epa.gov/OST/BASINS/gisdata.htmlEPA Data (RF3 data files) www.epa.gov/OST/BASINS/gisdata.html Ami Arthur aarthur@enterprise.nssl.noaa.govAmi Arthur aarthur@enterprise.nssl.noaa.gov Paul.Jendrowski@noaa.gov (SOO KHNL)Paul.Jendrowski@noaa.gov (SOO KHNL)

55. 55 AMBER Case Studies ftp 198.206.50.10 public buff.ppt 13Jul96buff.ppt 13Jul96 epgh99.ppt 18May99epgh99.ppt 18May99 pitcairn.ppt 01Jul97pitcairn.ppt 01Jul97 zion.ppt 27Jul98zion.ppt 27Jul98 ohio98.ppt 26Jun98ohio98.ppt 26Jun98 dallas95.ppt 05May95dallas95.ppt 05May95 ftc97.ppt 28Jul97ftc97.ppt 28Jul97 kc1998.ppt 05Oct98kc1998.ppt 05Oct98 Buffalo Creek, COBuffalo Creek, CO Pittsburgh, PAPittsburgh, PA Cedar City, UTCedar City, UT Eastern OhioEastern Ohio Dallas, TX*Dallas, TX* Fort Collins, CO*Fort Collins, CO* Kansas City, MO* * Tropical Z/R CasesKansas City, MO* * Tropical Z/R Cases