Selective ensemble mean technique for severe European windstorms.

We show that ensemble forecasts of extreme European windstorms can be improved up to a lead time of 36–48 hr by sub‐selecting ensemble members based on their performance at very short lead times (up to 12 hr). This applies to both the ensemble mean position of the cyclone centre and the ensemble windstorm footprint over the continent. A number of ensemble forecasts, including those from the ECMWF Ensemble Prediction System, are initialised every 12 hr and disseminated several hours after initialisation; therefore our approach has the potential to provide improved forecasts in an operational context. The analysis is performed on GEFS reforecast data. Mean error of the full ensemble mean forecasts of European windstorms (blue) and mean error of a sub‐ensemble created by performance selection at t = 12 hr (orange). The numbers in parentheses indicate the number of underlying cases. [ABSTRACT FROM AUTHOR]