A Study Of Flash Flood Occurrences At A Site Versus Over A Forecast Zone

"A flash flood is a flood in which the rapid rise in stream level and the resulting inundation follows the observable causative event by about four hours or less. For rain-caused flash floods meteorology is complex, and limited amounts of real-time data make timely forecasts of exact location very difficult. Lack of reports of flash-flood occurrences adds to the difficulty. Many occur that are never reported to the National Weather Service (NWS)"--Introduction.

The nation's network of more than 130 Next Generation Radars (NEXRADs) is used to detect wind and precipitation to help National Weather Service forecasters monitor and predict flash floods and other storms. This book assesses the performance of the Sulphur Mountain NEXRAD in Southern California, which has been scrutinized for its ability to detect precipitation in the atmosphere below 6000 feet. The book finds that the Sulphur Mountain NEXRAD provides crucial coverage of the lower atmosphere and is appropriately situated to assist the Los Angeles-Oxnard National Weather Service Forecast Office in successfully forecasting and warning of flash floods. The book concludes that, in general, NEXRAD technology is effective in mountainous terrain but can be improved.