Madden—Julian Oscillation prediction and teleconnections in the S2S database

The Madden—Julian Oscillation (MJO) has been diagnosed in the World Weather Research Program (WWRP)/World Climate Research Program (WCRP) Sub‐seasonal to Seasonal prediction project (S2S) database using the Wheeler and Hendon index over the common hindcast period 1999—2010. The S2S models display skill to predict the MJO over a period between two and four weeks. The majority of S2S models tend to produce a weaker MJO than in ERA‐Interim, with a phase speed decreasing with lead time. All the S2S models produce realistic patterns of MJO teleconnections at 500 hPa, with an increased probability of positive North Atlantic Oscillation (NAO) following an active MJO over the Indian Ocean and of negative NAO following an active MJO over the West Pacific. However, the amplitude of the MJO teleconnection patterns are significantly weaker than in ERA‐Interim over the Euro‐Atlantic sector and are often too strong over the western North Pacific. Models with lower horizontal resolution tend to produce weaker teleconnections. In the lower stratosphere, several S2S models produce teleconnections which are too strong compared to ERA‐Interim. These results suggest that, although the S2S models display significant skill in predicting the MJO propagation beyond two weeks, all the S2S models do not fully exploit the predictability associated with the MJO in the Northern Extratropics, particularly over Europe.