The two latest changes introduced during 1998 into the Ensemble Prediction
System (EPS) operational at the European Centre for Medium-Range Weather Fo
recasts (ECMWF) are described. The first change, the inclusion of instabili
ties growing during the data assimilation period in the generation of the E
PS initial perturbations increased the probability that the analysis lies i
nside the ensemble forecast range. The second change, the introduction of a
simulation of random model errors due to parametrized physical processes,
improved in particular the prediction of precipitation. The performance of
the ECMWF Ensemble Prediction System from 1 May 1994 to 2 March 1999 is ass
essed using different statistical measures. Results indicate that the gener
al performance of the EPS has been improving over the years. Finally, ongoi
ng research projects on predictability, issues developed either at ECMWF or
at European research institutes in collaboration with ECMWF are discussed.