Workshop on Predictability, dynamics and applications research using the TIGGE and S2S ensembles

ECMWF has been producing ensemble-based sub-seasonal forecasts since 2004. Sub-seasonal forecasts at ECMWF are based on 51-member ensemble integrations running twice a week for 46 days. An 11-member ensemble of re-forecasts covering the past 20 years is produced routinely to calibrate the real-time forecasts. This presentation will discuss its skill in predicting several sources of predictability, such as the MJO, sudden stratospheric warmings (SSWs) as well as a general assessment of tropical and extratropical skill scores and their evolution since 2004. The second part of the presentation will discuss possible improvements in the ECMWF sub-seasonal forecasting system: increased horizontal and vertical atmospheric resolution, SST bias correction, interactive aerosols and ozone, benefit of a lag ensemble generation.