Synopsis: Warm-episode conditions are expected to continue
into early 2005.
sea surface temperature (SST) anomalies greater than +0.5°C (~1°F) persisted across most of
the equatorial Pacific during October 2004 (Fig. 1). By
early November, positive equatorial SST anomalies greater than +1°C
(~2°F) were found from 160°E eastward to
150°W and locally in the area around 120°W (Fig. 2).
The increase and eastward expansion of the area of anomalous warmth
in the central and east-central equatorial Pacific during July-October (Fig.
3) indicates the early stages of a warm ( El Niņo)
late 2003 MJO activity has resulted in week-to-week and month-to-month
variability in many atmospheric and oceanic indices. In the past few months
the warmth in the central equatorial Pacific has supported eastward shifts
of enhanced convection associated with the convectively active phase of the
Madden-Julian Oscillation (MJO) across the western equatorial Pacific.
This activity has been associated with periods of weaker-than-average
easterlies that initiated eastward-propagating oceanic Kelvin waves. This
intraseasonal variability has been superposed on 1) an upward trend in SST
anomalies east of the date line (Fig. 3) and 2) a gradual increase in the
upper-ocean heat content during the last year (Fig. 4). 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 warm episode (El Niņo)
conditions will persist through early 2005.
global impacts include drier-than-average conditions over
Indonesia (through early 2005), northern and northeastern
Australia (November 2004-February 2005), and southeastern
Africa (November 2004-March 2005). If the warming in the tropical Pacific
strengthens and spreads eastward to the South American coast, then
wetter-than-average conditions would be expected in coastal sections of
Ecuador and northern Peru during the first few months of 2005, and
drier-than-average conditions would be expected to develop in the eastern
Amazon late this year and spread to Northeast Brazil during February through
Niņo wintertime impacts over the United States vary considerably depending on the character (distribution and intensity) of
the warming in the tropical Pacific. Composite impacts for selected ranges
of the ONI for El Niņo episodes since 1950 (Fig. 5) show that the areal
extent of warmer-than-average (wetter-than-average) conditions increases
across the northern (southern) United States, as the strength of El Niņo
increases. The current warming in the tropical Pacific is expected to
continue through the upcoming winter, with models indicating an ONI in the
range of +0.5ēC to +1.4ēC. Thus, the winter outlook for the United States
(Fig. 6) is a blend of the
composite impacts for comparable historical El Niņo episodes and the
effects of long-term trends. Warmer-than-average conditions are expected in
the West and in the northern Plains, while cooler and wetter-than-average
conditions are expected for portions of the South and Southeast.
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 9 December 2004. To receive
an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send
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