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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
December 12, 2002


Sea surface temperature (SST) anomalies (departures from average) increased in all of the Niņo regions in November (Fig. 1), as warm (El Niņo) episode conditions continued. Equatorial SST anomalies were greater than +1°C throughout most of the Pacific between 170°E and the South American coast, and exceeded +2°C between 180°W and 100°W (Fig. 2). Positive subsurface temperature departures and a deeper-than-average oceanic thermocline prevailed throughout the equatorial Pacific east of 180°W.

Atmospheric indicators of El Niņo include consistently negative values of the equatorial and Tahiti-Darwin Southern Oscillation Indices (EQSOI and SOI) since March 2002, and weaker-than-average low-level easterly winds since May 2002 throughout the equatorial Pacific (Fig. 3). The values of the EQSOI, 850-hPa zonal wind index, and the Niņo 3.4 index are considerably less in magnitude than those observed during the 1997-98 El Niņo (Fig.3).

Recent El Niņo-related impacts include: 1) above-average precipitation over the tropical Pacific, especially in the vicinity of the date line (180°W) since August 2002, 2) drier-than-average conditions over many sections of Indonesia, India, Mexico, Central America and northern South America, 3) drier-than-average conditions over the U.S. Pacific Northwest, and wetter-than-average conditions over the U.S. Gulf Coast (Fig. 4).

Based on the recent evolution of conditions in the tropical Pacific and on coupled model and statistical model forecasts, basin-wide warm (El Niņo) episode conditions are expected to continue through May 2003. Expected global conditions include: 1) drier-than-average over Indonesia and eastern Australia continuing during the next several months, 2) wetter-than-average over southeastern South America (Uruguay, northeastern Argentina, and southern Brazil) through the end of 2002, 3) drier-than-average over southeastern Africa during December 2002-March 2003, 4) drier-than-average over Northeast Brazil and northern South America during December 2002-April 2003, and 5) wetter-than-average conditions over coastal sections of Ecuador and northern Peru during January-April 2003. Over the United States and Canada, during winter 2002-2003, expected conditions include: 1) drier-than-average in the Ohio Valley states and northern U.S. Rockies, 2) wetter-than-average along much of the southern tier of the U.S., and 3) warmer-than-average in the northern tier states, southern and southeastern Alaska, and western and central Canada

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 (Weekly Update). Forecasts for the evolution of El Niņo/La Niņa 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:

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Page last modified: December 12, 2002
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