Current ENSO Information
ENSO Update
16 December 2002
Summary
The IRI's assessment is that there is a virtually 100% probability that
the current El Niño will continue for the remainder of 2002 and
into the first 2 to 4 months of 2003. This assessment is based on the collective
forecasts of various ENSO prediction models, as well as on the experience
of the several oceanographers and atmospheric scientists familiar with
the El Niño phenomenon. This probability is the same as that given
one month ago. This episode has become a moderate El Niño, but remains
significantly weaker than the 1997-98 event. The associated climate effects
in most regions are likely to be weaker than those experienced during the
1997-98 El Niño, but may nonetheless be substantial in some regions.
General Discussion
Between mid-November and mid-December, sea surface temperatures (SSTs)
in most of the east-central equatorial Pacific remained more than 1 degree
C above normal. In the central basin just east of the dateline, and also
farther east but still west of the South American coast, SSTs have been
as much as 2 to 3 degrees C above normal. SSTs off the west coast of South
America averaged about one-half degree above normal during late November
and early December. The SSTs immediately off the west coast of South America
are expected to warm further over the coming several months as the El Niño
episode completes the mature stage. The atmosphere continues to show many
features indicative of El Niño, including reduced easterly trade
winds in the western and central tropical Pacific, a lower than average
Southern Oscillation Index, and above average tropical rainfall from 155E
to 155W longitude. Near average SSTs and somewhat dry conditions continue
in parts of the far western Pacific and Indonesia. All of the above features
are consistent with the mature stage of El Niño.
SST forecasts from a large set of dynamical and statistical models support
the interpretation that we are in the mature stage of a moderate El Niño.
Relatively high skill is expected for the model forecasts at this time
of the year. Depending on the type of forecast model, between 88 and 100%
of the models predict El Niño conditions persisting into the January-February-March
period before returning toward neutral conditions. The remaining models
call for near-neutral SST throughout December of 2002 and into early 2003.
(Note
1) In summary, the models suggest that we are in the mature stage of
this El Niño episode that will continue into at least early 2003
before weakening significantly.
Note 1 - Only models that produce a
new ENSO forecast every month are included in the above statement.
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