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: El
El Niño is expected to
strengthen and last through the Northern Hemisphere
weak El Niño was present during July 2009, as monthly sea surface temperatures
(SST) departures ranged from +0.5°C to +1.5°C across the equatorial Pacific
Ocean, with the largest anomalies in the eastern half of the basin (Fig.
Consistent with this warmth, all of the Niño-region SST indices were between
+0.6°C to +1.0°C throughout the month (Table T2). Subsurface
oceanic heat content (average temperatures in the upper 300m of the ocean)
anomalies continued to reflect a deep layer of anomalous warmth between the
ocean surface and thermocline (Fig. T17). Also,
convection was suppressed over
and enhanced across
the western Pacific and near the International Date Line (Fig. T25).
In addition, developing El Niño’s often feature westerly wind bursts
over the western equatorial Pacific, such as the one which occurred at the end
of July (Fig. T13). These
oceanic and atmospheric anomalies reflect El Niño.
majority of the model forecasts for the Niño-3.4 SST index (Figs.
suggest El Niño will continue to strengthen.
While there is disagreement on its eventual strength, nearly all of the
dynamical models predict a moderate-to-strong El Niño during the Northern
Hemisphere Winter 2009-10. A
strengthening El Niño during the next few months is also suggested by the
recent westerly wind event in the western equatorial Pacific, which can lead to
additional anomalous warmth across the central and east-central equatorial
Pacific during the next two months. Therefore, current conditions and model
forecasts favor the continued development of a weak-to-moderate strength El Niño
into the Northern Hemisphere Fall 2009, with the likelihood of at least a
moderate strength El Niño (3-month Niño-3.4 SST index of +1.0°C or greater)
during the Northern Hemisphere Winter 2009-10.
updates of oceanic and atmospheric conditions are available on the Climate
Niño/La Niña Current Conditions and Expert Discussions).