CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
Alert System Status: La
expected to last at least through the Northern Hemisphere winter 2010-11.
Niña strengthened during August 2010, as negative sea surface temperature (SST)
anomalies reached at least -1°C across most of the equatorial Pacific Ocean by
the end of the month (Fig. T18). All of the Niño indices
were between –1°C and –1.5°C for the month of August (Table T2).
Consistent with this evolution, the subsurface heat content (average
temperatures in the upper 300m of the ocean) decreased further, reflecting the
additional cooling of sub-surface waters east of the Date Line (Fig. T17). Also convection was
enhanced over Indonesia, while remaining suppressed over the western and central
equatorial Pacific (Fig. T25). This pattern was associated
with a continuation of enhanced low-level easterly trade winds and anomalous
upper-level westerly winds over the western and central equatorial Pacific (Figs.
Collectively, these oceanic and atmospheric anomalies reflect
the strengthening of La Niña.
all models predict La Niña to continue at least through early 2011 (Figs.
However, the models continue to disagree on the eventual strength of La
Niña. Based on current observations
and model guidance, we expect the SST anomalies in the Niño-3.4 region to
either persist near the present strength, or to strengthen into the winter as is
consistent with the historical evolution of La Niña.
Thus, it is likely that the peak strength of this event will be at least
moderate (3-month average between –1°C to
–1.4°C in Niño-3.4) to strong (3-month average of –1.5°C or less
updates of oceanic and atmospheric conditions are available on the Climate
Niño/La Niña Current Conditions and Expert Discussions).