MJO Prediction at ECMWF

The skill of the ECMWF forecasting system to predict the Madden Julian Oscillation (MJ0) is monitored using the methodology described in Gottschalck et al.(2009). The current ECMWF forecasting system has skill to predict the evolution of the MJO for about 25 days, this skill depending on the strength and phase of the MJO in the initial conditions. An assessment of the skill of the dynamical forecasting system over the past 10 years shows a very significant and steady improvement of the ECMWF model to predict the MJO with a gain of bout 1 day of predictability per year. This improvement in the representation of the MJO in the ECMWF sub-seasonal forecasts has led to an improvement in the simulation of the impact of the MJO on tropical cyclones and extratropical weather. The contribution of various model changes (model resolution, changes to the model physics, ocean-atmosphere coupling, atmospheric initial conditions..) to the MJO skill scores will be discussed.