New radar technology may improve flash flood forecasting

Abstract

Between rain and hail lies the story. Recognizing the difference between the two forms of precipitation could provide more accurate—and possibly earlier—warnings of flash floods, such as those that have plagued parts of the U.S. West this summer. The NEXRAD, or WSR‐88D, Doppler National Weather Service (NWS) radars, which measure only the horizontal polarity of the precipitation, cannot distinguish between the two. But an experimental type of radar with dual‐polarimetry technology can tell the rain from the hail. While this polarimetric technology is no magic pill for protecting people and property from flash floods, it could make a big difference, according to some weather experts. Scientists currently are conducting field tests of the devices, and hope to convince federal funding agencies that the technology offers social and economic benefits significant enough to justify retrofitting NWS radars within a few years.