Hydrologic Application of the Tropical Cyclone Precipitation Climatology PAMS Mini-Technical Conference March 15, 2005 Jason Caldwell, HAS Forecaster Lower Mississippi River Forecast Center Slidell, LA Gloria Forthun, Regional Climatologist Southeast Regional Climate Center Columbia, SC

Provide river and flood forecasts and warnings for the protection of lives and property. Provide basic hydrologic forecast information for the nations environmental and economic well being. National Weather Service Hydrologic Services Program Mission

Hydrologic Services Program RIVER FORECAST CENTERS (RFCs) Strong Technical Support/Focus Calibrates/Maintains/Executes Hydrologic Forecast Models Works directly with some sophisticated water users (e.g., USACE, USGS, DWR, etc.) WEATHER FORECAST OFFICES (WFOs) Uses/Tailors RFC Forecasts/Services to Local Users River/Flood Forecast Watch/Warning Program Delivers Products/Services to the Local Media/Public

Two Main RFC Functions Operations Flood/River Forecasting Dam Break Support Flash Flood Support Snowmelt Forecasting Water Supply Forecasting Precipitation Forecasting Data QC Procedure Development Model Calibration Model Maintenance/Support Special Studies

forecast precip / temp Operational Flood Forecasting HASHAS River Forecast System parameters Observing Systems data Calibration model guidance Hydrologist hydrologic expertise & judgment bulletins graphics Flood Forecast Guidance

LMRFC AREA OF RESPONSIBILITY River/Precipitation Gage Network 220 Forecast Points (189 Daily, 31 Flood-only) Weekly 28-day Forecasts at 10 Locations Servicing 18 WFOs RNKGSP FFCMRX BNAHUN MEMPAH LSXSGF LITJAN TSASHV LIXMOB FWDLCH

WEB-BASED PRODUCTS OF THE RFC PRECIPITATION FLOODING

EXPANSION OF THE TROPICAL CYCLONE-INDUCED PRECIPITATION CLIMATOLOGY -ALL tropical cyclone landfalls from TX/Mexico border to Chincoteague, VA (TX,LA,AR,MS,AL,TN,NC,SC,VA,FL) -Period of record from Storm characteristics include: State(s) affected, direction of motion, speed of motion, storm intensity, and, potentially, synoptic interaction -Potential application to QPF and RVF at NWS WFOs and RFCs -WAAAYYY in the future……..a web- based application to develop the plots dynamically from the database

CLIMATOLOGICAL PRECIPITATION DATA INTERPOLATE TO GRIDDED DATA USING GIS GRID STATISTICS TO PRODUCE BASIN MAP USE HPC AND NHC FORECASTS TO DETERMINE START TIME TIME DISTRIBUTE THE DATA INTO 6HR VALUES CAVEATS -USED DAILY DATA TO COMPUTE STORM TOTAL PRECIPITATION -ONLY USED STATIONS WITH 100%; VARY BY STORM -ASSUMED T-DISTRIBUTION USING FEW HOURLY SITES -PRECIPITATION TIMING BASED ON FORECASTS W/ ERRORS DATA COLLECTION AND CLIMO QPF

0000UTC 29 AUGUST UTC 30 AUGUST 2005 HURRICANE KATRINA CASE STUDY

MISSISSIPPI MAJOR HURRICANES AndrewAugust 26-28, 1992 CarmenSeptember 7-9, 1974 OpalOctober 4-5, 1995 FredericSeptember 12-14, 1979 EloiseSeptember 22-24, 1975 ElenaSeptember 2-4, 1985

SITE SELECTION 361 Observation Sites Available Approximately 40% with 100% data

BIG BLACK FORECAST GROUP MODELED BASINS KilmichaelSBig Black WestFBig Black GoodmanSBig Black Way St/Hwy 16SBig Black BentoniaFBig Black BovinaFBig Black WillowsHBayou Pierre EddicetonSHomochitto RosettaFHomochitto WoodvilleHBuffalo F Forecast Point S Support Point HHeadwater

PERFORMING A CONTINGENCY FORECAST MAXIMUM PRECIPITATION PLOT INDICATED 2-6 ACROSS BIG BLACK FORECAST GROUP USED 72 QPF FROM HPC/LMRFC AND CLIMO MAX IN HYDROLOGIC MODELS USED 8/27 12UTC AS A STARTING POINT FOR FORECAST TO INCREASE LEAD TIME OF POTENTIAL RIVER FLOODING FIRST MUST TIME DISTRIBUTE THE MAX CLIMO PRECIPITATION FOR USE IN THE MODELS

NHC Forecast placed Katrina approx. 250NM from Big Black Forecast Group by 2AM 8/29 HPC/LMRFC QPF began at F42 from 8/27 12UTC grids Correlated to first 6- hour period ending 1AM 8/29 THE TIMING ISSUE

WHAT TO EXPECT FROM THE FORECASTS? MAX UNDER-PREDICTED ACROSS UPPER BIG BLACK FORECAST GROUP; OVER-PREDICTED LOWER HPC/LMRFC QPF PERFORMED WELL UPPER BIG BLACK; UNDER IN LOWER MAX PRODUCED HIGHEST QPF EARLIER THAN HPC/LMRFC WITH LESS SPREAD SO……WHAT DOES THIS MEAN? EXPECT BEST PERFORMANCE BY HPC/LMRFC IN BIG BLACK, BETTER PERFORMANCE ACROSS HOMOCHITTO BY MAX

MAX27 OBS OP27 CREST*=14.7 7am 9/1 CREST=16.6 7am 9/1 CREST=17.0 noon 9/1 WEST, MS FORECAST FROM 12UTC * *Still rising, not actual crest OBS=16.8 at 7am 9/1

BENTONIA, MS FORECAST FROM 12UTC MAX27 OBS OP27 CREST=13.5 7pm 8/30 CREST=16.0* 7am 9/1 CREST=19.5 7pm 8/31 *Still rising, not actual crest OBS=19.4 at 7am 9/1

BOVINA, MS FORECAST FROM 12UTC MAX27 OBS OP27 CREST*=13.5 7am 9/1 CREST*=13.0 7am 9/1 CREST=25.0 7pm 8/30 *Still rising, not actual crest OBS=22.8 at 7am 9/1

ROSETTA, MS FORECAST FROM 12UTC MAX27 OBS OP27 CREST=8.2 7am 8/30 CREST=8.2 7pm 8/30 CREST=5.4 7am 8/30 CREST=5.6 7am 8/31

MAX Under-Estimated Gage Heights MAX Performed Well Lower Forecast Group

CONCLUSIONS MAX under-predicted precipitation in Big Black, over- predicted in Homochitto HPC/LMRFC did good job in Big Black, under-predicted in Homochitto As a result, HPC/LMRFC river forecasts better across Big Black with best results from MAX in Homochitto Need to expand climatology to include similar track and speed storms regardless of intensity For contingency purposes in Katrina, climatology would have been safe bet for using 72 hours of QPF in forecast models without exceeding observed crests HOWEVER….. A contingency forecast should give a worst-case scenario given the current hydrometeorological conditions…… MAX FAILED AT THIS TASK ACROSS THE BIG BLACK

ACKNOWLEDGMENTS Southeast Regional Climate Center Gloria Forthun, Justin Glenn, Andy Brandenburg, and Michael Johnson South Carolina State Climatology Office National Climatic Data Center Dave Brandon, CBRFC Dave Reed, LMRFC

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