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Forecast Forum
SEPTEMBER 2007
Forecast Forum
The
CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
Outlook:
La Niña
will likely continue into early 2008.
Discussion:
La
Niña conditions strengthened during September 2007, as negative SST anomalies
along the equator expanded westward and now extend from 170ºE to the South
American coast (Fig. T9).
The monthly analysis shows the largest SST departures (-2ºC to -3ºC) between
100ºW and the coast, with departures of -0.5°C centered near the date line (Fig.
T18). The
magnitude of the negative SST anomalies increased in all of the Niño regions,
with the Niño-3.4 index dropping to -0.8°C and the Niño-4 index dropping to
-0.4°C (Table T2).
The upper-ocean heat content (average temperatures in the upper 300 m of the
ocean) in the central and east-central equatorial Pacific remained below average
during September, with temperatures ranging from 2°C to 4°C below average at
thermocline depth (Fig. T17). Consistent with these conditions, the low-level easterly winds and
upper-level westerly winds remained stronger than average across the central
equatorial Pacific (Figs. T20
and T21),
convection remained suppressed throughout the central and eastern equatorial
Pacific, and enhanced convection again covered parts of
Indonesia
and the far western Pacific (Fig. T25). Collectively, these oceanic and atmospheric conditions reflect a
strengthening La Niña.
The
recent SST forecasts (dynamical and statistical models) for the Niño 3.4 region indicate a weak-to-moderate La Niña continuing into early 2008 (Figs.
F1-F13). Current
atmospheric and oceanic conditions and recent trends indicate that La Niña will
continue and may strengthen during the next 3 months.
Weekly
updates of oceanic and atmospheric conditions are available on the Climate
Prediction
Center
homepage (El
Niño/La Niña Current Conditions and Expert Discussions).
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www.nws.noaa.gov
