NATIONAL-WEATHER-SERVICE WARNING PERFORMANCE-BASED ON THE WSR-88D

The National Weather Service (NWS) began operational use of the Weathe r Surveillance Radar-1 988 Doppler (WSR-88D) system in March 1991 at N orman, Oklahoma. WSR-88D data have been available to forecasters at fi ve additional offices: Melbourne, Florida, and Sterling, Virginia (sin ce January 1992); St. Louis, Missouri, and Dodge City, Kansas (since M arch 1992); and Houston, Texas (since April 1992). The performance of the severe local storm and flash flood warning programs at the six off ices before and after the availability of the WSR-88D was measured qua ntitatively. The verification procedures and statistical measures used in the quantitative evaluation were those used operationally by the N WS. The statistics show that the warnings improved dramatically when t he WSR-88D was in operation. Specifically, the probability of detectio n of severe weather events increased and the number of false alarms de creased. There was also a marked improvement in the lead time for all severe local storm and flash flood events. These improvements were evi dent throughout the effective range of the radar. Stratification of se vere local storm data by severe thunderstorms versus tornadoes reveale d an improvement in the NWS's ability to differentiate between tornadi c and nontornadic storms when the WSR-88D was in operation. Four indiv idual cases are examined to illustrate how forecasters used the WSR-88 D to achieve the improved results. These cases focus on the unique fea tures of the WSR-88D that provide an advantage over conventional NWS r adars.