Strong cold episode conditions (La Niņa) continued
in the tropical Pacific during January, as sea surface temperatures remained more than
1°C below normal throughout the equatorial Pacific between 170°E and 90°W (Fig. 1, top). These negative SST anomalies have been
accompanied by
stronger-than-normal low-level easterlies (Fig. 1, middle) and
reduced precipitation (positive OLR anomalies, Fig. 1, bottom).
These features have persisted since mid-1998.
The equatorial subsurface temperature structure has maintained a pattern that is
typical of the mature phase of cold episodes, with positive subsurface temperature
anomalies in the western equatorial Pacific and negative subsurface temperature anomalies
in the eastern equatorial Pacific (Fig. 2). Since December
1999,
there has been a slow eastward expansion of the positive subsurface anomalies into the
central Pacific, which indicates a slow build-up of heat in the equatorial region.
Historically, the "building-up" phase of the ENSO cycle has lasted between one
and two years before the subsequent development of warm (El Niņo) episode conditions.
The most recent NCEP coupled model forecasts and most other available coupled model and
statistical predictions support a slow transition out of the current cold episode, with
cold episode conditions weakening during the next few months and either neutral or weak
cold episode conditions occurring during the second half of 2000.
Weekly updates for SST, 850-hPa wind, and OLR are available on the Climate Prediction
Center homepage at: http://www.cpc.ncep.noaa.gov (Weekly Update).
Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
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5200 Auth Road
Camp Springs, MD 20746-4304
e-mail: vkousky@ncep.noaa.gov