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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
March 9, 2006
Spanish Version (Español -- Courtesy of INFOCLIMA, Peru)

Synopsis: La Niña conditions are expected to continue during the next 3-6 months.

The patterns of anomalous ocean temperatures, atmospheric circulation and precipitation are consistent in indicating La Niña conditions in the tropical Pacific. During February negative equatorial SST anomalies less than –0.5ºC were observed at most locations between 165ºE and 115ºW, while anomalies greater than +0.5ºC were restricted to the western equatorial Pacific between Indonesia and 155ºE and the eastern equatorial Pacific between 100ºW and the South American coast (Fig. 1). Negative SST departures were observed in all of the Niño regions, except for Niño 1+2 (Fig. 2). During February, SST anomalies increased in the extreme eastern equatorial Pacific and heavy rains occurred in some portions of Ecuador and northern Peru. Brief warming in the extreme eastern equatorial Pacific at this time of the year has been observed in previous years, including the La Niña years of 1999, 2000 and 2001.

During February above-average precipitation (negative OLR anomalies, Fig. 3, top panel) was observed over portions of Indonesia, the Philippines and along the South Pacific Convergence Zone (SPCZ), while below-average precipitation (positive OLR anomalies) was observed over the central equatorial Pacific. Stronger-than-average low-level (850-hPa) easterly winds (Fig. 3, middle panel) persisted over the central equatorial Pacific, and anomalous upper-level (200-hPa) cyclonic circulation centers were observed in both hemispheres (Fig. 3, bottom panel). The equatorial subsurface temperature anomaly pattern (negative anomalies in the central and eastern Pacific and positive anomalies in the western Pacific, Fig. 4) persisted during January-February 2006, and the basin-wide upper ocean heat content remained below-average (Fig. 5). These atmospheric and oceanic features are consistent with ongoing La Niña conditions.

Most of the statistical and coupled model forecasts indicate cooler-than-average conditions in the tropical Pacific through mid-2006. The spread of the most recent statistical and coupled model forecasts (weak La Niña to ENSO-neutral) indicates some uncertainty in the outlooks. However, current conditions (stronger-than-average easterly winds over the central equatorial Pacific and below-average upper-ocean heat content) and recent trends in observed oceanic conditions support continuation of La Nina conditions in the tropical Pacific during the next 3-6 months. Based on current conditions in the tropical Pacific, the most recent SST predictions, and on results from historical studies on the effects of cold episodes, we expect wetter-than-normal (drier-than-normal) conditions to prevail over northern Indonesia, the Philippines and Hawaii (central equatorial Pacific) during the next three months.

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 thermal structure are available on the Climate Prediction Center web page at (Weekly Update). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 6 April 2006. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message:

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Page Author: Climate Prediction Center Internet Team
Page last modified: January 12, 2006
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