As is the case for most AGCMs, this coupled model's atmospheric response to observed tropical Pacific SST is fairly reliable in the tropics but considerably less so in the extratropics. The extratropical response is most realistic during ENSO extremes. The nature of the model's mid-latitude atmospheric response to the ENSO state has been discussed in Livezey et al. While skillful prediction of the extratropical atmosphere is a major goal, a prerequisite is the ability to predict ENSO itself-the tropical Pacific SST anomaly field. Both SST forecasts and surface climate forecasts for North America are presented here.
Warm water continues to gradually build up beneath the surface in the western Pacific.
The AGCM forecast is the ensemble mean of 18 individual integrations, each using a different atmospheric initial condition. The nature and skill of the model's mid-latitude atmospheric response to the ENSO state is discussed in Livezey et al. Skill during non-ENSO years is not significantly different from zero. The expected forecast skill over the U.S., given a perfect SST forecast, is described in Livezey et al. When multiplied by the imperfect correlation skills for predicting tropical Pacific SST, these areal average skills drop accordingly.