Sea surface temperature (SST)
anomalies decreased in the equatorial Pacific everywhere east of the date
line during January 2005, resulting in decreases in all of the Niņo indices
with the exception of Niņo 4 (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 early February 2005, positive equatorial SST anomalies greater than
+0.5°C (~0.9°F) were found from 140°E eastward to 155°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, through December there was a lack of
persistent enhanced convection over the anomalously warm waters of the central equatorial Pacific, which
limited El Niņo-related impacts.
Since late 2003 MJO activity has resulted in
week-to-week and month-to-month variability in many atmospheric and oceanic
indices. The MJO activity weakened considerably during early November 2004
and remained weak through mid-December. During the last half of December the
MJO strengthened, as enhanced convection and precipitation over the Indian
Ocean shifted eastward across Indonesia into the western tropical Pacific.
Since early January enhanced convection has persisted in the western equatorial
Pacific and expanded eastward into the central equatorial Pacific (Fig. 4),
accompanied by a weakening of the low-level easterly winds over the region.
At this time it is not clear whether the recent enhanced convection and
weakening of the easterly winds in the central equatorial Pacific are
transient features (related to the MJO) or perhaps evidence of a coupling
between the anomalously warm waters and the overlying atmospheric
Based on the recent evolution of oceanic and atmospheric conditions and on a majority of the statistical and
coupled model forecasts, it seems most likely that weak warm episode (El Niņo)
conditions will gradually weaken during the next three months and that ENSO-neutral
conditions will prevail during the last half of 2005
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 3 March 2005. To receive
an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send
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