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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
July 11, 2001

Near-normal conditions prevailed across the tropical Pacific during June 2001, as SST anomalies were near zero and the low-level easterly winds were near normal over the central and western equatorial Pacific. Since February 2001 SSTs and SST anomalies have steadily increased in the central equatorial Pacific Niņo 4 region (Fig.1) rising to their highest levels since the 1997-98 warm (El Niņo) episode. In early July equatorial SST anomalies of 0.5°C were observed in many areas between 160°E and 130°W (Fig. 2).

Over the past two years there has been a gradual expansion of the area of positive equatorial subsurface temperature anomalies into the central Pacific and a gradual decrease in the strength and areal extent of the negative subsurface temperature anomalies in the eastern Pacific. This evolution is consistent with a slow decay of the subsurface thermal structure that characterizes the mature phase of cold episodes. Accompanying this evolution has been a gradual transition from negative to positive SST anomalies between 160°E and 120°W.

Near normal conditions are likely to continue in the tropical Pacific during the remainder of the northern summer. This assessment is consistent with most coupled model and statistical model predictions. Thereafter, most predictions indicate slightly warmer-than-normal conditions during late 2001 and early 2002.

Weekly updates for SST, 850-hPa wind, OLR and the equatorial subsurface temperature structure are available on the Climate Prediction Center homepage at: (Weekly Update).  Forecasts for the evolution of El Niņo/La Niņa are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. This ENSO Diagnostic Discussion, which replaces the ENSO Advisories, will appear regularly around the 10th of each month on the CPC web site.

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Page Author: Climate Prediction Center Internet Team
Page last modified: July 11, 2001
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