Influence of the North Atlantic Oscillation on the Forecast Skill of the Madden–Julian Oscillation

Based on the database of the Subseasonal to Seasonal (S2S) Prediction project of the World Weather Research Programme (WWRP) / World Climate Research Programme (WCRP), the influence of the North Atlantic Oscillation (NAO) on the forecast skill of the Madden‐Julian Oscillation (MJO) is investigated. It is found that for most S2S models the MJO forecast skill at a lead time of about 3-4 weeks is dependent on the NAO amplitude in the initial condition. A strong NAO leads to a better MJO forecast skill than a weak NAO. Most models are able to capture the MJO phase changes following strong and weak NAO events. These results confirm that there is a strong Northern extratropical influence on the MJO and its forecast skill.