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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
May 11, 2006

Spanish Version (Español -- Courtesy of INFOCLIMA, Peru)

Weekly ENSO Update (PDF, PPT) - updated Mondays

Synopsis: ENSO-neutral conditions are expected to prevail during the next 3-6 months.

The current patterns of anomalous ocean temperatures are consistent in indicating a return to ENSO-neutral conditions in the tropical Pacific. During April SSTs were close to average at most locations between Indonesia and 90ºW (Fig. 1), which is reflected in the near zero departures observed in all of the Niño regions, except for Niño 1+2 (Fig. 2). During the month, negative SST departures developed in the extreme eastern equatorial Pacific, which is a reversal from conditions observed during February-March.

During April above-average precipitation (negative OLR anomalies, Fig. 3, top panel) was observed over portions of Indonesia and northern Australia, while below-average precipitation (positive OLR anomalies) was observed over the central equatorial Pacific and the eastern tropical Pacific between the equator and 20ºN. Slightly 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). Although these atmospheric features are lingering effects of La Nina, they are weaker than in previous months. Since February the basin-wide upper ocean heat content has increased, becoming slightly positive in April (Fig. 4). Collectively, these atmospheric and oceanic features signal the demise of La Niña and a return to ENSO-neutral conditions.

Most of the statistical and coupled models predict ENSO-neutral conditions in the tropical Pacific through the end of 2006 (Fig. 5). However, the spread of these forecasts (weak La Niña to weak El Niño) indicates considerable uncertainty in the outlook for the last half of the 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 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 8 June 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 last modified: January 12, 2006
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