Abstract 001

Abstract ID: 001

Sub-seasonal prediction at ECMWF

Lead Author: Frederic Vitart
ECMWF, United Kingdom

Keywords: Forecasting, Skill, MJO, Forecast configuration, Teleconnections

Abstract: ECMWF produces operational sub-seasonal forecasts since 2004, which are now included in the S2S database. In the current configuration, the ECMWF extended-range forecasts are produced twice a week (every Monday and Thursday at 00Z) as an extension of the ECMWF medium-range forecasts and consist of a 51-member ensemble, integrated for 46 days, with an 18 km resolution up to day 15 and 36 km after day 15. This system will be upgraded in 2023 and run daily with 100 members, but with the same horizontal resolution (36 km) during the whole 46-day integration, separately from the 15-day ensemble which will be run twice daily at 9 km. The reforecast configuration (11 members, twice weekly) will also be upgraded. The main motivations behind these changes will be discussed.
The performance of this ECMWF extended-range forecasting system will be presented, with a particular focus on the representation and prediction of the main sources of S2S predictability, such as the MJO, and their impacts. One of the most important issues affecting S2S prediction over Europe is the inability of the model to represent adequately the MJO teleconnections over the North Atlantic sector. The impact of model biases in the representation of Pacific sub-tropical jet as well as the impact of errors associated to ocean-atmosphere coupling will be discussed.

Magdalena Balmaseda
Chris Roberts