Synopsis: A transition from ENSO-neutral to La Niņa
conditions is possible during the next 2-3 months.
The pattern of anomalously warm SSTs associated with El Niņo
disappeared from the equatorial Pacific east of the date line during February (compare top and bottom panels in
Fig. 1). By the end of the month, SSTs were near average in the vicinity of the date line, and below average over
the eastern equatorial Pacific between 140°W and the west coast of South America. Also, the main area of anomalously
warm SSTs along the equator had become centered well west of the date line, which is also consistent with the
disappearance of El Niņo.
The latest weekly SST departures have decreased to near 0.5ēC in
the Niņo 4 region and to near 0ēC in the Niņo 3.4 region, and have become slightly negative in the Niņo 3 and
Niņo 1+2 regions (Fig. 2). Accompanying this drop in SST anomalies, the equatorial upper-ocean heat content
(average temperature departures in the upper 300 m of the ocean) decreased rapidly during December 2006-January
2007 (Fig. 3), as the upper ocean cooled and negative temperature anomalies developed. These trends in surface and
subsurface ocean temperatures indicate that the warm (El Niņo) episode has ended and that conditions are becoming
favorable for La Niņa to develop.
Most of the statistical and coupled models, including the NCEP
Climate Forecast System (CFS) (Fig. 4), indicate additional anomalous cooling during the next 2-3 months. Some of
the forecast models, especially the CFS, indicate a rapid transition to La Niņa conditions during March-May 2007.
This scenario is supported by the latest surface and subsurface oceanic conditions, and the persistence of stronger
than-average low-level easterly winds over the central equatorial Pacific.
This discussion is a consolidated effort of NOAA and its
funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web
site (El Niņo/La Niņa Current
Conditions and Expert Discussions). Forecasts for the evolution of El Niņo/La Niņa are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 5 April 2007. To receive
an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message