Stormforecast.eu: real-time automated forecasts for hail and lightning based on post-processed NWP

The European Severe Storms Laboratory (ESSL) has developed logistic models (AR-CHaMo) for the occurrence of lightning and (very) large hail based on the ERA5 reanalysis, with the primary purpose of investigating long-term chance in severe weather occurrence. These models can, however, also be used in a forecasting context. 

We have set up a routine that uses AR-CHaMo models to post-process the output of three different NWP models, the ECMWF IFS HRES, DWD's ICON-EU, and NCEP's GFS to obtain probabilities of hail and lightning occurrence. The results were evaluated as a part of the ESSL Testbeds in 2022.

Forecast maps showing the calculated probabilities for the current and following day are calculated from the average of the three models and are made available on a website. The website interface allows overlaying reports from the European Severe Weather Database, which give an impression of the quality of the forecasts and help to identify existing weaknesses. Work is underway to include ensemble forecasts, and quantitative real-time verification, and to extend the forecast horizon as part of projects supported by the Austrian Science Fund and ECMWF. We show several AR-CHaMo lightning and large hail forecasts that resulted in no hail, large hail, and very large hail and discuss their performance.