Current atmospheric and oceanic conditions do not
support the development of La Niña in the next few months. Negative sea-surface temperature anomalies weakened
across the central and eastern equatorial Pacific during June (Fig. 1), resulting in an upward trend in SST
anomalies in all of the Niño regions (Fig. 2). By early-July equatorial SSTs were near or below normal between
150oW and the South American coast, and above normal west of 150oW (Fig. 1 bottom panel). Also, since late May
positive equatorial upper-ocean temperature departures have increased in magnitude in the western Pacific and
spread eastward into the central and eastern Pacific (Fig. 3). This evolving subsurface pattern is associated
with an eastward propagating oceanic Kelvin wave, resulting from a period of weaker-than-average easterlies in
the central equatorial Pacific that occurred during late May and early June. These recent trends in surface and
subsurface ocean temperature departures do not support the development of La Niña conditions during the next few
months. In addition, some atmospheric indices, such as the Tahiti-Darwin SOI (-1.1 in June) and low-level (850-hPa)
zonal wind in the central and eastern Pacific (negative in June), also do not support the development of La Niña
in the near future.
The latest statistical and coupled model forecasts
indicate considerable uncertainty for the next several months. However, the majority of the forecasts indicate near
neutral conditions (Nino 3.4 SST anomalies between -0.5oC and +0.5oC) during the last half of 2003.
This is consistent with current conditions and recent observed trends.
This discussion is a consolidated effort of NOAA and its
funded institutions. Weekly updates for SST, 850-hPa wind, OLR and features of the equatorial subsurface
temperature structure are available on the Climate Prediction Center web page at
http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for the evolution of
El Niņo/La Niņa are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. To receive
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