Local versus remote wind forcing of the equatorial Pacific surface temperature in July 2003

After the moderate El Niño of 2002 the tropical Pacific seemed poised to enter a La Niña phase. Wind anomalies during May and June 2003, however, led to a sudden termination of this event. Counter to earlier predictions, forecasts from July 2003 correctly predicted normal conditions for the remainder of the year. In this paper the causes of this abrupt turn of events are analyzed. It is shown that wind anomalies in the eastern tropical Pacific played a major role in terminating the incipient cold ENSO phase. Although westerly wind bursts in the western Pacific explained most of the ocean subsurface behavior to the west of 110°W, their impact on SST was confined to the central equatorial Pacific.