Model forecasted departure from normal temperatures across the mid to high latitudes of the Northern Hemisphere, including Europe and East Asia for January, February and March 2004. Forecast was generated in December 2003, the AER forecast was derived using observed autumnal snow cover anomalies in Siberia and other observed autumnal atmospheric variables. Credit: Judah Cohen, AER, Inc.

Observed departure from normal temperatures across the mid tohigh latitudes of the Northern Hemisphere for January, February and March 2004. Credit: Judah Cohen, AER, Inc.

The new seasonal forecast model has been continuously updated and tested using hindcasts and real-time forecasts. In addition to incorporating data on sea surface temperature, stratospheric conditions and snow cover extent, other inputs into the forecasts include anomalies from the fall season such as regional temperature and sea level pressure anomalies, and the propagation of energy associated with large atmospheric waves known as Rossby waves.