Sea surface temperature(SST) anomalies decreased in all of the Niņo regions during February 2005
(Fig. 1). However,
positive sea surface temperature (SST) anomalies greater than +1°C
(~1.8°F) persisted in portions of the central and western equatorial
Pacific (Fig. 2). By late February 2005, positive
equatorial SST anomalies greater than +0.5°C (~0.9°F) were found from 155°E eastward to 165°W
(Fig. 3). The pattern of anomalous
warmth in the equatorial Pacific in recent months and the most recent
5-month running mean value of the Southern Oscillation Index (-0.5) indicate
that a weak warm (mid-Pacific El Niņo)
episode is in progress.
However, the recent decrease in SST anomalies throughout the equatorial
Pacific suggests that a return to ENSO-neutral conditions is taking place.
In spite of the recent trend in SST
anomalies, drier-than-average conditions prevailed over
during February, while enhanced convection and precipitation persisted over
the anomalously warm waters of the central equatorial Pacific (Fig.
panel). This enhanced convection has been accompanied by strong low-level
westerly wind anomalies (Fig. 4, bottom panel) that initiated an
eastward-propagating oceanic Kelvin wave (Fig. 5). This wave appears to be
stronger than those that have occurred in recent months in association with
MJO activity. At this time there is uncertainty concerning the possible
influence of this latest Kelvin wave on the surface and subsurface
conditions in the eastern equatorial Pacific.
Based on the recent evolution of
SST anomalies and on a majority of the statistical and coupled model
forecasts, it seems most likely that weak warm episode (El Niņo) conditions will
continue to weaken during the next three months
and that ENSO-neutral conditions will prevail during the northern summer.
Some lingering effects of the weak warm episode, such as drier-than-average
conditions over portions of Indonesia, may continue to be experienced for the next month or two.
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
thermal 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 the Forecast Forum
section of CPC's Climate Diagnostics Bulletin. The
next ENSO Diagnostics Discussion is scheduled for 7 April 2005. To receive
an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send
your e-mail address to: email@example.com.