Moderate warm episode (El Niño) conditions continued
during September 2002, as SST anomalies (departures from average) remained
greater than +1°C throughout the central equatorial Pacific between 180°W
and 125°W (Fig. 1), and positive subsurface
temperature departures and a deeper-than-average oceanic thermocline
prevailed throughout most of the equatorial Pacific (Fig.
2). Atmospheric indicators of El Niño include consistently negative
values of the Southern Oscillation Index (SOI) since March 2002, and
weaker-than-average low-level easterly winds (positive 850-hPa zonal wind
departures) since May 2002 throughout the
equatorial Pacific (Fig. 3). In addition,
above-average precipitation has been observed over the tropical Pacific,
especially in the vicinity of the date line (180°W), while
drier-than-average conditions prevailed over many sections of Indonesia,
India, Mexico and Central America (Fig. 4). These
oceanic and atmospheric conditions indicate the presence of El Niño.
Most coupled model and statistical model forecasts indicate that El Niño
conditions will continue through early 2003. Based on the recent evolution
of conditions in the tropical Pacific, we expect SST anomalies to increase
further in the eastern equatorial Pacific (Niño 3 and Niño 1+2 regions),
with the establishment of basin-wide mature El Niño conditions during
December 2002-February 2003. Furthermore, based on the latest predictions and
an assessment of current oceanic and atmospheric conditions, we expect that
this event will be substantially weaker than the 1997-98 El Niño. Thus, the
global impacts should generally be weaker than those observed during
1997-98. However, strong impacts are still possible in a few locations.
Expected global impacts include: 1) drier-than-average conditions over
Indonesia and eastern Australia continuing during the next several months,
2) wetter-than-average conditions over southeastern South America (Uruguay,
northeastern Argentina, and southern Brazil) during the next three months,
3) drier-than-average conditions over southeastern Africa during December
2002-February 2003, and 4) wetter-than-average conditions over coastal
sections of Ecuador and northern Peru during December 2002-April 2003. Over
the United States and Canada we expect: 1) drier-than-average conditions in
the Pacific Northwest and mid-Atlantic states during fall 2002 and in the
Ohio Valley states and northern Rockies during winter 2002-2003, 2)
wetter-than-average conditions along much of the southern tier of the U.S.
during winter 2002-2003, and 3) warmer-than-average conditions in the
northern tier states, southern and southeastern Alaska, and western and
central Canada during late fall 2002 and winter 2002-2003.
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 Niño/La Niña are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. To receive
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