IRI ENSO Update / Forecast
Technical ENSO Update
Summary of Model Forecasts
18 January 2006
SummaryCooler than average sea surface temperatures continue to develop in the eastern and central equatorial Pacific, and as of mid-January La Nina conditions are currently observed. Based on the latest observations and forecasts, the probability of a La Nina event over the Jan-Feb-Mar 2006 season is 50%.
General DiscussionDuring December 2006, sea surface temperatures (SSTs) were approximately 1.0C below average in the eastern Pacific and approximately 0.5C above average in the western Pacific. The extent and magnitude of the colder than average conditions in the eastern Pacific have been increasing since mid-November due to coupled growth of ocean-atmosphere anomalies. There are now sufficient changes in the upper ocean thermal structure to maintain the cool SST conditions at least through the next several months. If the current conditions were to persist through March, a La Niña event would be acknowledged. Out of a large set of dynamical and statistical forecast models, none predicts sea surface temperatures reaching even weak El Niño levels through northern spring 2006. Overall, based on model forecasts and current observations of the ocean surface and subsurface, the probability of a La Niña event for the next season is approximately 50%, decreasing to climatological probabilities of 25% by mid-2006. The chances for developing El Niño conditions are estimated at approximately 2% through April 2006, increasing to 25% by mid-2006.