Dr. Amanda Schroeder NWS Weather Forecast Office Fort Worth, TX Sustainable Urban Water Workshop University of Texas-Arlington June 4-5, 2015
Outline Communicating the message - official Flood and Flash Flood issuances Concerns in the Metroplex Recent Metroplex flooding 2
Nationwide Trends http://www.nws.noaa.gov/om/hazstats.shtml In 2013, floods were: 2 nd deadliest U.S. weather-related hazard behind heatrelated deaths Single deadliest U.S. convective weatherrelated hazard over the 30-yr. avg. (1984-2013)
Communicating the Message Flash Flood Watch Urban and Small Stream Flood Advisory Flash Flood Warning Flash Flood Emergency Haltom City, TX June 18, 2007 Photo Credit: Fort Worth Star- Telegram 8
Flash Flood Watch Current or forecast hydrometeorological conditions are favorable for heavy rain & flash flooding in the watch area Avg size 46,000 km 2 (18,000 mi 2 ) Issued ~ 24-36 hours in advance of expected heavy rain Example of a Flash Flood Watch Heavy rainfall of 2-4 inches may lead to flash flooding in the green highlighted region tomorrow night 9
Flash Flood Watch - tools Observed or forecast atmospheric moisture profiles Conceptual models (fronts) and forecaster expertise Numerical Model Output National NWS guidance Consideration for existing soil moisture (e.g. FFG) HPC graphic 10
Flash Flood Warning Widely disseminated text product informs the public, emergency managers, and other agencies that flash flooding is imminent or is occurring. Avg size 3000 km 2 (1200 mi 2 ) Issued when radar or rain gauge reports indicate excessive rainfall rates or when dam/levee breaks expected BULLETIN - EAS ACTIVATION REQUESTED FLASH FLOOD WARNING NATIONAL WEATHER SERVICE FORT WORTH TX 1115 AM CDT TUE MAR 18 2008 THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A * FLASH FLOOD WARNING FOR... DALLAS COUNTY IN NORTH CENTRAL TEXAS EASTERN TARRANT COUNTY IN NORTH CENTRAL TEXAS * UNTIL 215 PM CDT * AT 1115 AM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED THUNDERSTORMS WITH HEAVY RAIN ALONG A LINE EXTENDING FROM GARLAND TO ARLINGTON MOVING NORTHEAST AT 15 MPH. RADAR INDICATES THAT 1 TO 2 INCHES OF RAIN HAS ALREADY FALLEN. ANOTHER 1 TO 2 INCHES WILL BE POSSIBLE THROUGH 215 PM CDT. LAT...LON 3299 9723 3299 9652 3259 9656 3257 9728 11
Flash Flood Warning - Tools Radar reflectivity and rainfall trends Rain gauge reports Report of dam or levee failure Flooding reports Decision assistance tool (FFMP) compares radar rainfall estimates with RFC flash flood guidance Forecaster knowledge of flood prone areas FFMP Estimate of 3-hr rainfall on 18 June 2007. Heaviest rain indicated on upstream basins of White s Branch of Big Fossil Creek. 12
Flash Flood Warning - Tools May 29, 2015 ~ 5 AM CDT 13
Flash Flood Warning - Tools May 29, 2015 ~ 5 AM CDT Dual-Pol Estimates Legacy Estimates 14
Flash Flood Monitoring and Prediction (FFMP) Tool An integrated suite of applications which analyzes and monitors precipitation Runs on AWIPS workstations Generates short-term warning guidance for Flash Flooding Supplements forecaster event monitoring Conducts precipitation analyses in a basin world : all calculations are performed over the areas of small basins Avg basin size 13 km 2 (5 mi 2 ) Example of FFMP output 18 June 2007 15
FFMP How It Works Maps FFG to small basins Compares radar estimated rainfall to FFG in each basin Threat tables and maps highlight basins where rainfall > FFG Source: 1-hr, 3-hr, 6-hr FFG from RFC Typical sources: dual-pol QPE, legacy 88D precip estimate, etc Diff column gives amount of runoff (+) or add l rain needed (-) to cause FF
Flash Flood Emergency Exceedingly rare issuance Consists of a special headline in a Flash Flood Warning or Statement Must be clear evidence that people have been placed in life-threatening situations by rapidly rising floodwaters Trusted report from EM, broadcast media, law enforcement could prompt FFE issuance Photo Credit: KSPR-TV Springfield MO...THIS IS A FLASH FLOOD EMERGENCY FOR SOUTHERN SPRINGFIELD... AT 1255 PM CDT...LOCAL LAW ENFORCEMENT OFFICIALS REPORTED SLOW MOVING THUNDERSTORMS WITH VERY HEAVY RAINFALL ACROSS THE WARNED AREA. EMERGENCY MANAGEMENT AND LOCAL LAW ENFORCEMENT IS REPORTING HOMES BEING FLOODED ALONG WITH NUMEROUS FLOODED ROADWAYS AND HIGH WATER RESCUES ONGOING IN SOUTHERN GREENE COUTY AND SOUTH SPRINGFIELD. UP TO NINE INCHES OF RAINFALL HAS FALLEN IN THE FLASH FLOOD EMERGENCY AREA AND ADDITIONAL HEAVY RAINFALL IS EXPECTED. 17
Flood Warnings Site Specific NWS WFO runs site specific model for fast response creeks and streams Flooding at these sites generally less of a threat to life than Flash Flooding Response times < 6 hrs Site Specific basins across north Texas 18
Flood Warnings DWRT2 White Rock Creek flows into White Rock Lake NE of downtown Dallas Forecasters adjust rainfall and QPF to instantly produce first guess hydrograph If expected to exceed Flood Stage, WFO will issue FLW for the event Option to use SAC-SMA or API for model Sample of Site Specific Model run for DWRT2; the basin is shown in the inset image. User adjusts pcpn/qpf in top panel and model output is shown with flood categories in large middle panel. 19
Concerns in the Metroplex Potential for catastrophic flash flooding is substantial Mayfest 1995: 17 FF fatalities Hail + Flooding: $2B Rainfall rate: 5 cm/15 min NWS mission:..weather, hydrologic, forecasts and warnings for the protection of life and property NWS radar image of Mayfest Storm Copyright 1995 - Samuel D. Barricklow 20
Flash Flood Warnings from April 13 May 30, 2015 46 FFWs for Dallas/Tarrant/Denton/ Collin 38 NEW and 8 EXT Most were on or after May 24, 2015 21
Recent Metroplex Flooding Rowlette Creek Sachse White Rock Creek Dallas 22
Recent Metroplex Flooding WFAA Fort Worth Star- Telegram WFAA Assoc. Press USA Today Longview News Journal WFAA 23
Acknowledgements This presentation was derived from a presentation given by Greg Patrick in 2013. Photo Credits, as noted on each slide, include Fort Worth Star-Telegram, WFAA, Associated Press, USA Today, KSPR-TV, and Samuel D. Barricklow 24
Questions/Comments? amanda.schroeder@noaa.gov 817-429-2631 25