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Forecast Forum
DECEMBER 2009
Forecast Forum
The
CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
ENSO
Alert System Status: El
Niņo Advisory
Outlook:
El Niņo is expected to
continue at least into the Northern Hemisphere Spring 2010.
Discussion:
El
Niņo strengthened during December 2009, with above-average sea surface
temperatures (SST) encompassing the central and eastern equatorial
Pacific Ocean
(Fig. T18). The Niņo-3.4 index
increased slightly with the most recent monthly value reaching +1.8°C (Table
T2).
Consistent with this warmth, equatorial upper-ocean heat content
anomalies remained positive. Subsurface
temperature anomalies exceeded +2°C across much of the equatorial Pacific (Fig.
T17),
with the largest departures seen in the eastern part of the basin at the end of
the month. Equatorial low-level
westerly and upper-level easterly wind anomalies were also consistent with El Niņo
(Figs. T20, T21),
along with a continuation of suppressed convection over Indonesia and enhanced
convection over the western and central equatorial Pacific (Fig. T25).
Collectively, these oceanic and atmospheric anomalies reflect a strong El
Niņo.
The
models continue to disagree on the eventual peak strength of El Niņo (Figs.
F1-F13).
At this time, it is expected that the 3-month Niņo-3.4 SST average will
exceed +1.5°C during the winter (e.g. November-December-January and
December-January-February). Regardless
of its precise peak strength, El Niņo is expected to exert a significant
influence on the global weather and climate in the coming months.
Most models indicate that SST anomalies in the Niņo-3.4 region will
begin to decrease in early 2010, and that El Niņo will persist through
April-May-June 2010.
Weekly
updates of oceanic and atmospheric conditions are available on the Climate
Prediction
Center
homepage (El
Niņo/La Niņa Current Conditions and Expert Discussions).
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www.nws.noaa.gov
