Warm episode (El Niņo)
conditions continued during January 2003, as equatorial SST anomalies
remained greater than +1°C
in the central equatorial Pacific (175°E-125°W,
Fig. 1). In addition, enhanced precipitation and cloudiness were observed
over the central tropical Pacific (Fig. 2), and positive subsurface
temperature departures (Fig. 3) and a deeper-than-average oceanic
thermocline were observed throughout the equatorial Pacific east of 180°W.
These conditions are consistent with mature warm episode conditions.
During January 2003 there were indications that the warm episode is
beginning to weaken. Sea-surface temperature anomalies decreased throughout
the eastern equatorial Pacific by as much as 1.5°C
during the month (Fig. 4), while equatorial easterly winds were near normal
throughout the central and eastern equatorial Pacific. Over the past several
weeks there has also been a steady eastward progression of negative
subsurface temperature anomalies, indicating a gradual depletion of the
excess warmth in the upper ocean of the equatorial Pacific. This evolution
is typical during the mature phase of warm episodes.
Recent values of atmospheric and oceanic indices, such as the SOI,
850-hPa zonal wind index, Niņo
1+2 are all considerably smaller in magnitude than those observed during the
1997-98 El Niņo (Fig. 5). The warming associated with the current event has been greatest in
the central equatorial Pacific (Niņo
4 and Niņo
3.4 regions). Regions farther east (e.g., Niņo
3 and especially Niņo
1+2) have warmed much less. A comparison with previous warm episodes in the
last 50 years (Fig. 6) indicates that, for the equatorial Pacific as a
whole, the current event is moderate in intensity.
Consistent with current conditions and recent observed trends, most
coupled model and statistical model forecasts indicate that El Niņo
conditions will continue to weaken through April 2003. Thereafter, the
consensus forecast is for near-normal conditions during May-October 2003.
Those areas of the world usually affected by El Niņo
may continue to experience related impacts during the next 2-3 months.
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
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
an e-mail notification when updated ENSO Diagnostic Discussions are released please send
your e-mail address to: