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 Niņo is expected to
continue strengthening and last through at least the Northern Hemisphere
October 2009, sea surface temperature (SST) anomalies increased across the
central and eastern equatorial
The monthly Niņo-3.4 index increased to +1.0°C (Table T2).
Above-average subsurface temperature anomalies increased across a large
region of the central and east-central Pacific, with anomalies ranging between
+1 to +5°C by the end of the month (Fig. T17).
Consistent with this warming, subsurface oceanic heat content anomalies
(average departures in the upper 300m of the ocean) also increased during the
month. In addition, low-level
westerly and upper-level easterly wind anomalies strengthened over much of the
equatorial Pacific (Fig. T20 and
The pattern of tropical convection also remained consistent with El Niņo,
with enhanced convection over the west-central Pacific and suppressed convection
Collectively, these oceanic and atmospheric anomalies reflect a strengthening El
continues to be disagreement among the models on the eventual strength of El Niņo,
but the majority indicate that the three-month average Niņo-3.4 SST index value
will range between +1.0°C and +1.5°C during the Northern Hemisphere winter (Figs.
Consistent with the historical evolution of El Niņo, a peak in SST
anomalies is expected during November-January.
Presently, there is considerable uncertainty over how long this event
will persist. Most of the models suggest El Niņo will last through March-May
2010, although the most likely outcome is that it will peak with at least
moderate strength (3-month Niņo-3.4 SST index of +1.0°C or greater) and last
through at least the Northern Hemisphere winter 2009-10.
updates of oceanic and atmospheric conditions are available on the Climate
Niņo/La Niņa Current Conditions and Expert Discussions).