Current ENSO Information

ENSO Update

15 November 2002

Summary

The IRI's assessment is that there is a virtually 100% probability that El Niño conditions will continue for the remainder of 2002 and into early 2003. This assessment is based on the collective forecasts of various ENSO prediction models, as well as on the experience of the several oceanographers and atmospheric scientists familiar with the El Niño phenomenon. This probability is the same as that given one month ago. It is most likely that this will remain a moderate El Niño, which is significantly weaker than the 1997-98 event. The associated climate effects in most regions are expected to be weaker than those associated with the 1997-98 El Niño, but may nonetheless be substantial in some regions.

General Discussion

Between mid-October and mid-November, sea surface temperatures (SSTs) in most of the east-central equatorial Pacific remained more than 1 degree C above normal, with the warmest SSTs between 2 and 3 degrees C above normal over the central basin just east of the dateline as well as farther east but still west of the South American coast. SSTs in the far eastern Pacific have warmed to become slightly above normal in recent weeks. While SSTs off the west coast of South America averaged only about one-quarter degree above normal for the month of October, they warmed to more than one-half degree above normal during late October and early November and are expected to warm further over the coming several months as the El Nino episode matures. The atmosphere continues to show all features indicative of El Niño, including reduced easterly trade winds in the western and central tropical Pacific, a lower than average Southern Oscillation Index, and above average tropical rainfall from 150E to 150W longitude. Near or below normal SSTs and unusually dry conditions continue in parts of the far western Pacific and Indonesia. All of the above features indicate that the El Niño is entering the mature stage.

SST forecasts from a large set of dynamical and statistical forecast models support the interpretation that we are nearing the mature stage of a moderate El Niño. Relatively high skill is expected for the model forecasts at this time of the year. Depending on the type of forecast model, between 93 and 100% of the models predict El Niño conditions persisting into the December-January-February period and continuing into early Northern Hemisphere spring of 2003. The remaining model calls for near-neutral SST throughout 2002 and into early 2003. (Note 1 ) The models clearly suggest that we are in a maturing El Niño episode that will continue into at least early 2003. 

Note 1 - Only models that produce a new ENSO forecast every month are included in the above statement.