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ENSO Quick Look
ENSO Update21 October 2004SummaryOverall conditions in the tropical Pacific are currently indicative of a weak El Niño. Based on the latest observations and forecasts, it is at least 60% likely that weak El Niño conditions will prevail through early 2005.General DiscussionWeak El Niño conditions developed in the
east-central tropical Pacific
in late July. Sea surface temperatures of 1 degree C above
average are now observed along the equator from 160E to 145W. Sea
surface
temperatures in
the far eastern tropical Pacific have warmed from below normal to
nearly average levels. The tropical Pacific atmospheric
conditions have begun to show
some characteristics of El Niño development, but more weakly
than those of the ocean. Out of a large set of
dynamical and
statistical
forecast models, about two-thirds predict sea surface temperatures at
weak El
Niño levels for the coming season, and a few of the
models presently showing only borderline El Niño conditions warm
to that
level by the end of the year, indicating approximately 70% probability
of weak El Niño conditions by early 2005.
Overall, based on model forecasts and current observations of
the ocean surface and subsurface, the chances for El Niño
conditions are aproximately equal to 60% from October through
December 2004, increasing to 70% by the end of the calendar
year and
into early 2005, and decreasing thereafter. The likelihood
of neutral conditions is below the climatological
likelihood (i.e. less than 50% probability) through 2004
and early 2005. The
probability of development
of La Niña conditions is believed to be much less than that
of an average year (i.e. less than 25%).
Note 1 - Only models that produce a new ENSO forecast every month are included in the above statement.
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