Seasonal Forecast of tropical storms at ECMWF

A 30-member ensemble of 6-month integrations of a coupled T63 GCM is realized every month. An objective procedure for tracking model tropical storms is applied on each member of the ensemble during the six months of integrations. The statistics on tropical storm frequency, intensity and position are compared to a 66-member ensemble climatology. A WMW-test is then applied to determine if the coupled GCM forecasts a significant signal in tropical storm statistics for the next season. A validation of hindcasts for the period 1991 to 1998 indicates a particularly strong skill over the western North Pacific and western North Atlantic.