The NWS QPF Verification Program

The U.S. Weather Research Program and the National Weather Service (NWS) have identified precipitation estimates and forecasts as a priority for improvement in the operational and research communities. Objective assessment and quantification of the skill of quantitative precipitation forecasts (QPFs) in the NWS QPF process are necessary to identify the value added at each step and to assist in improving the forecasts. As a result, the NWS has recently outlined a uniform national precipitation verification program and created the National Precipitation Verification Unit (NPVU) to fulfill these requirements. The NPVU will beceom operational by October 2000. Verification statistics from the NPVU will serve to support NWS programmatic decisions and NWP model changes, provide feedback to individual forecasters and forecast offices, and ultimately improve QPFs and associated products. The success of the program is dependent upon the real-time availability of all QPFs and high-quality precipitation estimates.

The (prototype) NPVU participated in the NWS QPF Process Assessment by providing objective QPF verification. The NPVU is currently participating in the Western Region Follow-on Assessment and provides monthly updates of verification statistics. QPF verification methodologies and results from the above assessments will presented as well as the implications of the results. It has been found that modifications to traditional QPF verification methodologies and measures provide more information about the quality of the QPFs. The NPVU currently provides QPF verification to the HPC of their 06-h, 24-h, and 5-day QPFs. Details of the NWS QPF verification program, including QPF verification methods and measures and their usefulness, will be presented.