CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
ENSO-neutral conditions are
ENSO-neutral conditions continued during August 2008,
as recent increases in sea surface temperatures (SSTs) abated across the
. Above-average SSTs in the
east-central and eastern Pacific diminished, while below-average SSTs in the
central Pacific strengthened slightly (Fig. T18). From
west to east, the monthly SST index values range
from −0.3°C in the Niņo-4
region to +1.1°C in the Niņo 1+2 region (Table
subsurface oceanic heat content (average temperatures in the upper 300m of the ocean) also decreased in response to the emergence
of negative temperature anomalies at thermocline depth in the east-central
Pacific (Fig. T17).
conditions have been in place since June 2008, the atmospheric circulation over
the western and central tropical Pacific continues to reflect lingering 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). Despite
this lingering La Niņa signal in the atmosphere, the overall atmospheric and
oceanic system is consistent with ENSO-neutral conditions.
Most of the dynamical and statistical SST forecasts
for the Niņo
3.4 region indicate a continuation of ENSO-neutral conditions
(−0.5°C to 0.5°C in the Niņo-3.4 region) through the Northern Hemisphere Spring 2009 (Figs.
F1- F13). While the model spread
continues to include the possibility of an El Niņo, the decrease in subsurface
and surface temperatures makes this outcome unlikely during the next several
months. In addition, the
redevelopment of negative temperature anomalies at thermocline depth and the
historical tendency for multi-year La Niņa episodes means that even a return to
weak La Niņa conditions is possible. However,
based on current atmospheric and oceanic conditions, recent trends, and model
forecasts, ENSO-neutral conditions are expected to continue through the end of
updates of oceanic and atmospheric conditions are available on the Climate
Niņo/La Niņa Current Conditions and Expert Discussions).