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Synopsis: El Niño conditions have developed and are likely to continue into early 2007.

By early September equatorial SST anomalies greater than +0.5ºC were observed in most of the equatorial Pacific, with anomalies exceeding +1.0ºC in the central Pacific between 165ºE and 170ºW (Fig. 1). The latest SST departures in the Niño regions are all greater than +0.5 (Fig. 2). Beginning in February the basin-wide upper ocean heat content increased, and since early April positive anomalies have been observed (Fig. 3). Since early July weaker-than-average low-level equatorial easterly winds have been observed across most of the equatorial Pacific. In August the Southern Oscillation Index (SOI) was negative for the fourth consecutive month. Collectively, these oceanic and atmospheric anomalies are consistent with developing warm episode (El Niño) conditions in the tropical Pacific.

Over the past several months most of the statistical and coupled model forecasts have trended towards warmer conditions in the tropical Pacific through the Northern Hemisphere winter. The latest NCEP coupled forecast system (CFS) predictions indicate El Niño conditions for the remainder of 2006 and into the NH spring 2007 (Fig. 4). More than half of the other statistical and coupled model predictions are also favoring El Niño conditions during the same period. The recent conditions (weaker-than-average easterly winds over the central equatorial Pacific) and warming trends in observed oceanic conditions support these predictions.

Some impacts from the developing El Niño are already evident in the pattern of tropical precipitation. During the last 30 days drier-than-average conditions have been observed across all of Indonesia, Malaysia and most of the Philippines, which are usually the first areas to experience ENSO-related impacts. This dryness can be expected to continue, on average, for the remainder of 2006.

Typical El Niño effects are likely to develop over North America during the upcoming winter season. Those include warmer-than-average temperatures over western and central Canada, and over the western and northern United States. Wetter-than-average conditions are likely over portions of the U.S. Gulf Coast and Florida, while drier-than-average conditions can be expected in the Ohio Valley, the Pacific Northwest, and most of the U.S.-affiliated islands in the north tropical 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 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 5 October 2006. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message: ncep.list.enso-update@noaa.gov.