Current ENSO Information
ENSO Update
18 April 2003
Summary
The El Niño of 2002-03 has now nearly dissipated to neutral conditions,
and the remaining slightly warmer than normal sea surface temperatures are
likely to decrease further during the mid-April to June period.
The outlook beyond June 2003 is more uncertain. Based on the behavior
of past El Niño events and current model forecasts, it is most likely
that conditions will be near-neutral during the second half of 2003. Through
the end of May, lingering climate effects associated with the nearly
disspiated El Nino are expected to be weak.
General Discussion
Between mid-March and mid-April, sea surface temperatures (SSTs) have
weakened from above normal to neutral levels in much of the east-central
equatorial Pacific, but have remained more than one-half degree C above normal
near and just east of the dateline. By most standards, the El Nino has
now dissipated. The atmosphere continues, however, to show some features
indicative of El Niño, such as a slightly lower than average Southern
Oscillation Index and somewhat above average tropical rainfall from about
165E to 175W longitude.
SST forecasts from a large set of dynamical and statistical models indicate
that the moderate El Niño of 2002-03 is finished, and that the
remaining weakly warmer than average SSTs will continue to cool further.
The skill of SST forecast models is relatively low at this time of the year,
so that the forecasts beyond May do not have high confidence. Many of the models
indicate a high likelihood of neutral conditions through June.
By the July-August-September period, the models diverge in opinion, with 30%
calling for continuing weak El Niño conditions, 50% for neutral
conditions and 20% for La Niña conditions. (Note
1) In summary, the models suggest that the El Niño episode of 2002-03
has ended, and that the SST will weaken further and remain at neutral levels.
The outlook for middle and later 2003 currently
has high uncertainty.
Note 1 - Only models that produce a
new ENSO forecast every month are included in the above statement.
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