The patterns of anomalous ocean temperatures,
atmospheric circulation and precipitation are consistent in indicating La Niña
conditions in the tropical Pacific.
During February negative equatorial SST anomalies less than –0.5ºC were
observed at most locations between 165ºE and 115ºW, while anomalies greater
than +0.5ºC were restricted to the western equatorial Pacific between
Indonesia and 155ºE and the eastern equatorial Pacific between 100ºW and
the South American coast (Fig. 1). Negative
SST departures were observed in all of the Niño regions, except for Niño
1+2 (Fig. 2). During February, SST anomalies increased in the extreme eastern
equatorial Pacific and heavy rains occurred in some portions of Ecuador
and northern Peru. Brief warming in the extreme eastern equatorial Pacific at this time of the
year has been observed in previous years, including the La Niña
years of 1999, 2000 and 2001.
During February above-average precipitation (negative OLR anomalies, Fig.
panel) was observed over portions of Indonesia, the Philippines
and along the South Pacific Convergence Zone (SPCZ), while below-average
precipitation (positive OLR anomalies) was observed over the central
equatorial Pacific. Stronger-than-average low-level (850-hPa) easterly winds
(Fig. 3, middle panel) persisted over the central equatorial Pacific, and
anomalous upper-level (200-hPa) cyclonic circulation centers were observed in
both hemispheres (Fig. 3, bottom panel). The equatorial subsurface
temperature anomaly pattern (negative anomalies in the central and eastern
Pacific and positive anomalies in the western Pacific, Fig.
during January-February 2006, and the basin-wide upper ocean heat content
remained below-average (Fig. 5). These atmospheric and oceanic features are
consistent with ongoing La Niña conditions.
the statistical and coupled model forecasts indicate cooler-than-average
conditions in the tropical Pacific through mid-2006. The spread of the most
recent statistical and coupled model forecasts (weak La Niña to ENSO-neutral)
indicates some uncertainty in the outlooks. However, current conditions
(stronger-than-average easterly winds over the
central equatorial Pacific and below-average upper-ocean heat content) and
recent trends in observed oceanic conditions support continuation of La Nina
conditions in the tropical Pacific during the next 3-6 months. Based on current
conditions in the tropical Pacific, the most recent SST
predictions, and on results from historical studies on the effects of cold
episodes, we expect wetter-than-normal (drier-than-normal) conditions to
prevail over northern Indonesia, the Philippines and Hawaii
(central equatorial Pacific) during the next three months.
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 thermal 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 Niño/La Niña are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for