Warm episode (El Niño) conditions continued to weaken during February 2003, as SST anomalies decreased throughout the eastern and central equatorial Pacific (Fig. 1). Since December, SST anomalies have decreased by more than 2°C in the eastern equatorial Pacific between 130°W and the South American coast (Fig. 1, bottom panel). This decrease has resulted in near normal or slightly below normal SSTs in the region east of 120°W during February (Fig. 1, middle panel). Since December there has also been a steady decrease in the magnitude and extent of the positive subsurface temperature anomalies, indicating a depletion of the excess warmth in the upper ocean of the equatorial Pacific (Fig. 2). This evolution is typical during the decay phases of warm episodes.

In spite of these trends, significant positive SST anomalies in the central equatorial Pacific continued during February 2003, with anomalies greater than +1°C extending from 170°E to 150°W. In addition, enhanced precipitation and cloudiness were found over this region and some atmospheric circulation indices, such as the SOI, continued to reflect warm (El Niño) episode conditions.

Consistent with current conditions and recent observed trends, most coupled model and statistical model forecasts indicate that El Niño conditions will continue to weaken through March 2003. Thereafter, the consensus forecast is for near-normal conditions during April-October 2003. However, there is a wide spread amongst the individual forecasts, with some indicating the possibility of continued weak El Niño conditions and others indicating the development of La Niña conditions during the last half of 2003. The recent cooling of the upper ocean (surface and subsurface) in the eastern equatorial Pacific supports the possibility of the development of La Niña later this year.

This discussion is a consolidated effort of NOAA and its funded institutions. Weekly updates for SST, 850-hPa wind, OLR and features of the equatorial subsurface temperature structure are available on the Climate Prediction Center web page at http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for the evolution of El Niño/La Niña are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. To receive an e-mail notification when updated ENSO Diagnostic Discussions are released please send your e-mail address to: