El Niño conditions are likely to continue through May

Synopsis: El Niño conditions are likely to continue through May 2007. Equatorial Pacific SST anomalies greater than +1ºC were observed in most of the equatorial Pacific between 170ºE and the South American coast (Fig. 1). The latest SST departures in the Niño regions are between 1.1ºC and 1.3ºC, except for Niño 1+2 (Fig. 2). The increase in SST anomalies during the last several months has been accompanied by weaker-than-average low-level equatorial easterly winds across most of the equatorial Pacific and negative values of the Southern Oscillation Index (SOI). Collectively, these oceanic and atmospheric anomalies are consistent with the early stages of El Niño in the tropical Pacific.

Beginning in February 2006 the basin-wide upper ocean heat content increased, and since early April 2006 positive anomalies have been observed (Fig. 3). The upper ocean heat content has been modulated by oceanic Kelvin wave activity (Fig. 4), initiated by variations in the intensity of the low-level equatorial easterly winds. Four distinct Kelvin waves have occurred in the last several months (Fig. 4), with the amplitude of each wave exceeding that of its predecessor. The most recent Kelvin wave (bottom of Fig. 4) is expected to affect the west coast of South America during the last half of December 2006, resulting in a substantial warming of the subsurface and surface waters along the coasts of Ecuador and northern Peru.

Most of the statistical and coupled model forecasts, including the NCEP Climate forecast System (CFS), indicate that El Niño conditions will peak during the NH winter (December 2006-February 2007), followed by weakening during March-May 2007 (Fig. 5).

Typical El Niño effects are likely over North America during January-March 2007, including warmer-than-average temperatures over western and central Canada, and over the northwestern and northern United States, wetter-than-average conditions over portions of the U.S. Gulf Coast and Florida, and drier-than-average conditions in the Ohio Valley and in portions of the Pacific Northwest. Global effects that can be expected during December-March include drier-than-average conditions over most of Malaysia, Indonesia, northern and eastern Australia, some of the U.S.-affiliated islands in the tropical North Pacific, northern South America and southeastern Africa, and wetter-than-average conditions over equatorial East Africa, central South America (Uruguay, northeastern Argentina, southeastern Paraguay and southern Brazil) and along the coasts of Ecuador and northern Peru.

This discussion is a consolidated effort of NOAA and its funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center website (El Niño/La Niña Current Conditions and Expert Discussions). 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 11 January 2007. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
Camp Springs, MD 20746-4304