EuroTEPS— a targeted version of ECMWF EPS for the European area

Abstract

A global ensemble prediction system (EPS) needs initial perturbations to account for the uncertainties in the analysis. In this study singular vectors (SVs) are used to create these perturbations. In the operational EPS at the European Centre for Medium-Range Weather Forecasts (ECMWF) the SVs are computed over the whole globe. The aim of this study is to evaluate the possible benefit of complementing the regular SVs with higher resolution SVs that are targeted to three European areas after 24 h. The system thus adds perturbations that puts Europe in focus, and produces ensemble spread, in our area of interest for short-range forecasts without spending computational resources on ensemble spread elsewhere. This system is called European Targeted Ensemble Prediction System (EuroTEPS), and is evaluated and compared to ECMWF’s operational EPS over Europe for 9 weeks in 2008. The spread/skill relationship for mean sea level pressure is better for EuroTEPS than for EPS, and there is a considerable reduction in the ensemble mean forecast error. For most parameters and scores, EuroTEPS is comparable or better than ECMWF EPS over the European region for the first two forecast days. Further developments of the system are suggested.