Verification of the National Digital Forecast Database (NDFD) forecasts has been a high priority issue with NDFD, especially as a part of the Operational Readiness Demonstration (ORD). A prototype system for verifying maximum and minimum temperatures and probability of precipitation (PoP) was developed and used during the ORD. The verification consisted of a standard "point-to-point"comparison of forecasts taken from the NDFD grid to observations, as well as a preliminary "gridded" verification, where forecasts for the entire NDFD grid were compared to an analysis. For the prototype, RUC 20 km grid analyses of surface temperature were chosen for the analysis fields for verifying NDFD surface temperatures.

Three types of displays were developed to show ORD verification statistics. For the CONUS and each NWS CONUS region, maps of mean absolute error (MAE) or bias were generated for maximum and minimum temperature and maps of Brier score were generated for verifying probability of precipitation. Plots of statistical measures (MAE and bias for maximum and minimum temperature and Brier score for PoP) vs. forecast projection constitute the second type of display generated. Finally, statistics are presented in text format, grouped by CONUS, NWS Regions, and by individual observation site. These data are stored in GIS format to enable users to import them into local GIS's.

We anticipate that this prototype verification will be the basis for a monthly verification of NDFD forecasts, expanded to include other variables (3-hourly surface temperatures, dewpoint temperatures, and winds).