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Sea surface temperature (SST) anomalies continued to increase in the central
equatorial Pacific during July 2001. Since February 2001 SSTs and SST anomalies have steadily increased in the central equatorial Pacific
Ni�o 4 region (Fig. 1) rising to their highest levels since the 1997-98 warm (El Ni�o) episode. By late July equatorial SST anomalies
between 0.5�C and 1�C were observed between 165�E and 135�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 the decay of the subsurface thermal structure that characterizes the mature phase of cold episodes and the
development of conditions usually found just prior to warm episodes. Accompanying this evolution has been a gradual transition from negative to
positive SST anomalies between 160�E and 130�W.
Positive SST anomalies are likely to continue in the equatorial Pacific during the remainder of 2001 and into the first half of 2002. This assessment
is consistent with most coupled model and statistical model predictions that indicate warmer than normal oceanic conditions through early 2002.
The impacts that this warming will have on global temperature and precipitation patterns depend to a large degree on its intensity. At the moment,
there is considerable spread in the predicted SST anomalies, with most predictions indicating a weak or moderate warm episode (El Ni�o) by the
end of 2001 and the beginning of 2002.
Weekly updates for SST, 850-hPa wind, OLR and the
equatorial subsurface temperature structure are available on the Climate Prediction Center homepage
at: http://www.cpc.ncep.noaa.gov (Weekly Update).
Forecasts for the evolution of El Ni�o/La Ni�a 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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www.nws.noaa.gov
