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<br />000492 <br />H ENZ KELLY & ASSOCIATES <br />Weather Forecasting and Consulting <br /> <br />"WHEN IT MATTERS.. . BEFORE THE FACT" <br /> <br />Executive summary of key points presented by Henz Kelly & Associates in <br />Colorado Springs - March 12, 1986. <br /> <br />The Flash Flood Prediction Program Approach - Seven Years of Success <br /> <br />A. The Denver Flash Flood Prediction (F2-P2) Experience <br /> <br />* Denver F2-P2 run for the Urban Drainage & Flood Control District <br />since 1979, <br /> <br />* Operational results of the seven years - <br /> <br />-95% accurate forecast of flash flooding situations and thunderstorm <br />heavy rai ns <br /> <br />-False alarm rate of 20% for 7 years, 15% last 3 years <br /> <br />-No events went un-forecast past 6 years <br /> <br />-Lead-times of 4 hours or more for major events, 1-2 hours for <br />lesser events <br /> <br />B, Significant Storm experiences of past 5 years <br /> <br />* June 3, 1981.. .The Denver Tornado Outbreak... <br /> <br />-Anticipated 24 hours in advance <br />-Forecast 2-4" rains, large hail and tornadoes within the UDFCD <br />by 1000L <br />-Site-specific forecasts issued to individual counties from <br />l300-1630l as storm developed <br />-Urgent updates issued before tornado and heavy rains began <br />over Lakewood and Thornton/Northg1enn <br /> <br />* July 24/25 1983...4-6" Upper Cherry Creek Rai ns. . . <br /> <br />-Predicted 4-6" thunderstorm rains in the upper Cherry Creek basin <br />to Douglas County Sheriff office 2 hours in advance <br />-Bridges were monitored and closed to public as necessary...one <br />bridge washed out, two damaged <br /> <br />* June 13, 1984...Denver Mega-Rain/Hail Storm... <br /> <br />-Correctly anticipated severe situation and placed public forecast <br />in Rocky Mountain News <br />-By 1130L predicted two waves of severe thunderstorms to cross <br />northern Jefferson County and western Adams County from 1430-l730l <br />with 2-4" rains, 6-12" pea-size hail to clog drains, larger hail <br />over 1" in diameter and serious flooding threat. <br />-$350 million damage, 3-4.25" rains, serious flooding in Arvada, <br />Westminster, Wheatridge and Lakewood, 1-3.5" diameter hail <br /> <br />1776 South Jackson Street. Denver, Colorado 60210' (303) 759-1947 <br />