Since January 2001 there has been a gradual weakening of
La Niņa conditions in the tropical Pacific, as negative sea surface temperature (SST) anomalies have
decreased in magnitude and low-level winds have trended toward normal. By May 2001 near-neutral ENSO
conditions were evident, as SST anomalies were near zero and the low-level easterly anomalies were
weak over the central and western equatorial Pacific.
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 (Fig.1). 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 an eastward shift and weakening of
the magnitude of the negative SST anomalies (Fig. 2).
Near normal conditions are likely to prevail in the tropical Pacific during the northern
summer. This assessment is consistent with most coupled model and statistical model predictions.
Thereafter, most predictions indicate near-normal or 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: http://www.cpc.ncep.noaa.gov (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.