Making probability of precipitation (PoP) forecasts is an inherently complicated task where the forecaster must meld the probability of rain developing somewhere in the area with the expected areal coverage of that rain if it develops. As with most forecasts, a comprehensive, real-time verification program can help a forecaster improve his or her skill at the task. Unfortunately, traditional verification of PoP forecasts, using a few widely scattered observation sites, leaves much to be desired. First, much of the forecast area, and often entire zones, go completely without verification, leading forecasters to focus on the few verification points rather than the entire area. Also, several months of data must be gathered and processed in order to determine representative statistics. Finally, traditional verification of PoP forecasts is of limited value as a learning tool for forecasters since it is not done in real-time. Clearly, a better verification method is needed and has now been developed at WFO Tulsa.
Areal coverage of precipitation for 12-hour periods is available from Stage III precipitation data produced at the Arkansas/Red Basin River forecast Center (ABRFC). These data are being used to provide forecasters at WFO Tulsa with immediate feedback on the previous day's PoP forecast. A graphical interface has been developed to allow forecasters to view the percentage of area coverage for each county/zone in the forecast area. Through this interface, forecasters can view tables for each county that show not only the percentage of areal coverage, but also PoP forecasts valid for that time. Persistent consideration of such verification data should promote greater forecaster awareness of areal coverage in determining zone groupings and specific PoP forecasts. Preliminary verification statistics using summer-time areal precipitation data instead of point precipitation data will illustrate the potential benefits of this alternate verification scheme