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
conditions are likely to develop during July – August 2010.
June 2010, sea surface temperature (SST) anomalies continued to decrease across
the equatorial Pacific Ocean, with negative anomalies expanding across the
central and eastern Pacific (Fig. T18). While the rate of decrease
slowed during June, all of the Niño indices were cooler compared to the
previous month (Table T2). The subsurface heat content
(average temperatures in the upper 300m of the ocean) also remained
below-average during the month. Subsurface
temperature anomalies became increasingly negative in the east-central
equatorial Pacific and extended to the surface across the eastern half of the
basin (Fig. T17). Also during June, enhanced
convection persisted over Indonesia, while the area of suppressed convection
strengthened and expanded westward over the western and central equatorial
Pacific (Fig. T25). Enhanced low-level easterly
trade winds and anomalous upper-level westerly winds prevailed over the western
and central equatorial Pacific (Figs. T20,
these oceanic and atmospheric anomalies reflect developing La Niña conditions.
The majority of models now predict La Niña
conditions (SST anomalies less than or equal to -0.5°C in the Niño-3.4 region)
to develop during June-August and to continue through early 2011 (Figs.
Confidence in this outcome is reinforced by the recent performance of the
NCEP Climate Forecast System (CFS), the large reservoir of colder-than-average
subsurface water, and signs of coupling with the atmospheric circulation.
Therefore, La Niña conditions are likely to develop during July-August
updates of oceanic and atmospheric conditions are available on the Climate
Niño/La Niña Current Conditions and Expert Discussions).