Current ENSO Information
ENSO Update
18 March 2003
Summary
The current El Niño has weakened since late December 2002, and is
expected to continue to weaken or dissipate 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 April, climate effects in most regions are most likely to be
weaker than those experienced during early 1998 when the strong 1998 El
Niño was reaching its end, but they could still be substantial in
some regions (as some already have been). Regions commonly affected by
El Niño at this time of year should remain alert to the possibility
of such climate effects.
General Discussion
Between mid-January and mid-March, sea surface temperatures (SSTs) have
weakened from their moderately above normal levels in much of the east-central
equatorial Pacific, but have remained more than 1 degree C above normal
near and just east of the dateline. During the last few weeks, the atmosphere
continues to show features indicative of El Niño, such as a slightly
lower than average Southern Oscillation Index and above average tropical
rainfall from about 170E to 155W longitude.
SST forecasts from a large set of dynamical and statistical models indicate
that we are in the declining phase of this moderate El Niño. Relatively
high skill is expected for only the first one to two months of the model
forecasts at this time of the year, followed by lower skill from May onward.
Most of the models indicate a weakening of the El Niño through April.
By the July-August-September period, the models diverge in opinion, with 25%
calling for continuing weak El Niño conditions, 69% for neutral
conditions and 6% for La Niña conditions. (Note
1) In summary, the models suggest that this El Niño episode
is likely in its last one to two months before weakening to 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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