Predicting daily mean wind speed in Europe weeks ahead from MJO status

The Madden–Julian oscillation (MJO), a prominent feature of the tropical atmospheric circulation at subseasonal time scales, is known to modulate atmospheric variability in the Euro-Atlantic region. However, current subseasonal prediction systems fail to accurately reproduce the physical processes involved in these teleconnection mechanisms. This paper explores the observed impact of strong MJO events on surface wind speed over Europe. It is found that some MJO phases are accompanied by strong wind anomalies in Europe. After showing that this teleconnective mechanism is not present in the predictions of the ECMWF monthly forecasting system, a methodology to reconstruct forecasts of daily mean wind speed in the continent weeks ahead is proposed. This method combines MJO forecasts from the S2S project database and the observed teleconnection impacts in the historical records. Although it is found that strong MJO events cannot be skillfully predicted more than 10 days ahead with current prediction systems, a theoretical experiment shows that this method can effectively transform a dynamical MJO forecast into a probabilistic wind speed prediction in Europe.The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation program under Grant 776787 (S2S4E) and from the Ministerio de Ciencia, Innovación y Universidades (MICINN) as part of the CLINSA project (CGL2017-85791-R). The authors acknowledge Australian Bureau of Meteorology for providing the MJO RMM historical indices, and the S2S project for providing the MJO indices from ECMWF MFS forecasts and ERA-Interim. The authors want to thank Nicolau Manubens for technical support with the startR R package, which allows processing big memory arrays by chunks in a cluster and then merges the results back together. Many analyses would have not been possible without this package. The CSTools R package was also used to produce some figures. Pierre-Antoine Bretonnière and Margarida Samsó helped downloading and formatting the surface wind datasets. The authors want to thank Frederic Vitart and Laura Ferranti for helping with the interpretation of some results, and Verónica Torralba for helping to structure the material.Peer ReviewedPostprint (published version