The Use of Dual Polarization Radar Precipitation Products during a Small Scale Urban Flash Flood

During the evening hours of May 12th, 2015, slow moving thunderstorms over southeast Harris County became nearly stationary and produced 6 to 12 inches of rainfall in 3 hours. This heavy rainfall occurred over a small area (25 square miles) near NASA in Clear Lake, TX. The result was a rapidly developing major flood across an urban area. Numerous vehicles became stranded in deep flowing water along several major roadways with numerous high water rescues. One flash flood vehicle fatality occurred when a car was washed off of a highway and into a flooded drainage ditch.

Although real time rainfall gauges are located across this area as part of the Harris County Flood Control District's rainfall gauge network, the closest gauge missed the heaviest rainfall, recording 6.2 inches in 3 hours which is approximately half of the maximum occurring only a few miles away (11.98 inches from a NASA employee's home weather station). Instantaneous, hourly, and storm total dual polarization precipitation estimates were accurate, and proved to be critical in providing timely flash flood warnings for this small, severely impacted urban area. This presentation will highlight the value of these products during a rapidly developing, small scale flash flood event.