Warm episode (El Niņo) conditions prevailed during
July, as SST anomalies (departures from average) remained greater than +1°C throughout
the central equatorial Pacific between 170°E and 120°W (Fig. 1).
Atmospheric indicators of a warm episode (El Niņo) include consistently negative values
of the Southern Oscillation Index (SOI), since March 2002, and weaker-than-average
low-level easterly winds during May-July 2002 throughout the equatorial Pacific.
The Madden-Julian Oscillation (MJO) continues to be a major source of week-to-week and
month-to-month variability in the atmospheric circulation of the Tropics and subtropics.
The MJO contributed to a substantial weakening of the low-level easterly winds throughout
the equatorial Pacific during July. As a consequence, drier-than-average conditions were
observed over Indonesia and portions of Southeast Asia/ India during the month (Fig. 2). In addition, the weaker-than-average easterly winds
contributed to a deepening of the oceanic thermocline in the central equatorial Pacific,
evident by the increase in subsurface temperature anomalies (Fig. 3),
and an increase in SST anomalies in the central equatorial Pacific (Fig.
4) during July.
The oceanic and atmospheric variables discussed above reflect the presence of
weak-to-moderate El Niņo conditions. Most coupled model and statistical model forecasts
indicate that El Niņo conditions are likely to continue through the end of 2002 and into
early 2003. Although there is considerable uncertainty in the forecasts about the timing
and intensity of the peak of this warm episode, all of the forecasts indicate that it will
be much weaker than the 1997-98 El Niņo. It is important to add that the global impacts
of this warm episode should be correspondingly weaker than those observed during the very
strong 1997-98 El Niņo.
Based on the current conditions in the tropical Pacific, on the SST predictions, and on
results from historical studies of the effects of ENSO, we expect drier-than-average
conditions to continue over Indonesia and eastern Australia during the next several
months, and wetter-than-average conditions over southeastern South America during the next
This discussion is a team effort of NOAA and its
funded institutions. Updates of SST, 850-hPa wind, OLR and the equatorial subsurface
temperature structure are available on the Climate Prediction Center web page 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. To receive
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