ENSO Update

Synopsis: ENSO-neutral conditions are expected to continue for the next one to two months, with weak warm episode (El Niño) conditions likely by the end of 2006.

By the end of August 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). Correspondingly, the SST departures in the Niño regions were all positive (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 were observed across most of the equatorial Pacific, and the Southern Oscillation Index (SOI) was negative for the fourth consecutive month. Collectively, these oceanic and atmospheric anomalies are consistent with a trend toward 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 spread of the most recent statistical and coupled model forecasts (ENSO-neutral to weak El Niño) indicates some uncertainty in the outlooks (Fig. 4). However, recent conditions (weaker-than-average easterly winds over the central equatorial Pacific) and warming trends in observed oceanic conditions support a continuation of ENSO-neutral conditions for the next one to two months, with weak warm episode (El Niño) conditions likely by the end of 2006.

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.