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Forecast Forum
JULY 2008
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.
Outlook:
ENSO-neutral conditions are
expected
to
continue
through
the
Northern Hemisphere Fall 2008.
Discussion:
ENSO-neutral conditions continued during July 2008,
as sea surface temperatures (SSTs) in the central equatorial
Pacific Ocean
remained near-average (Fig.
T18). As is typical with ENSO-neutral
conditions, atmospheric and oceanic indicators were mixed, with certain areas in
the equatorial Pacific Ocean suggesting a lingering influence of La Niņa and
others reflecting an increase in above-average temperatures, particularly in the
eastern Pacific.
From west to east, the monthly SST index values range from −0.3°C in the Niņo-4 region to
+0.8°C in the Niņo 1+2 region (Table T2). The subsurface oceanic heat
content (average temperatures in the upper 300m of the ocean) has also increased in response to positive temperature anomalies along
the thermocline (Fig. T17).
However, a weak, shallow region of below-average temperatures still
remains near the International Date Line.
The atmospheric circulation over the western and
central tropical Pacific continues to reflect some aspects of La Niņa.
Enhanced low-level easterly winds and upper-level westerly winds persist
in this region (Figs. T20 and T21), while convection remains generally
suppressed over the central Pacific (Fig. T25). In contrast, the eastern
equatorial Pacific features weak-to-average low-level easterly winds and average
precipitation. Despite recent
increases in SST anomalies, the actual SSTs are not warm enough to support
convection (Fig. T18).
Collectively, these atmospheric and oceanic anomalies are consistent with
ENSO-neutral conditions.
Most of the recent dynamical and statistical SST
forecasts for the Niņo 3.4 region indicate ENSO-neutral conditions
(−0.5 to 0.5 in the Niņo-3.4 region) will continue into the Northern
Hemisphere Spring 2009 (Figs. F1- F13).
However, due to the positive heat content anomalies in the
Pacific Ocean
, the development of El Niņo cannot be ruled out during the later part of
the year, although chances remain low. Based
on current atmospheric and oceanic conditions, recent trends, and model
forecasts, ENSO-neutral conditions are expected to continue through the Northern
Hemisphere Fall 2008.
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
