Development of a MOS Thunderstorm System for the ECMWF Model
Equations for the probability of a thunderstorm and the conditional probability of a severe thunderstorm for 3-, 6-, 12-, and 24-h periods were developed over the CONUS from six years of ECWMF model output. Cloud-to-ground (CG) lightning data from the National Lightning Detection Network (NLDN) and severe weather reports collected by the Office of Climate Water and Weather Services (OCWWS) were used to define the predictand. Results from a k-fold cross-validation test indicate the new ECMWF thunderstorm guidance is superior to corresponding GFS MOS and NAM MOS forecasts, and in some cases, forecast skill and good reliability are achieved out as far as 240 hours in advance. This guidance will be incorporated into the experimental short-range and extended-range ECMWF MOS text bulletins which are restricted to NOAA/NWS use only, and will also be available to NWS forecasters in gridded format as part of an experimental ECMWF gridded MOS suite.