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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update18 January 2007SummaryAs of mid-January the sea surface temperature (SST) anomalies remain 0.5C above average throughout the equatorial Pacific, and in the eastern Pacific they exceed 1.5C above average. Although warm enough to maintain El Niño designation, the equatorial SST anomalies have weakened considerably since mid-December, especially in the central Pacific. Based on the latest observations and forecasts, the probability of maintaining El Niño conditions through the January-February-March 2007 season is approximately 85%.General DiscussionSince mid-September SSTs in the central and in the eastern equatorial Pacific have indicated El Niño conditions. Temperatures near the dateline and in the east Pacific appear to have peaked in early December. Over the last month, central Pacific SSTs have dropped from 1.5C to 0.5C above average. SSTs in the eastern Pacific have also declined, though less dramatically, and currently remain greater than 1.5C above average. The declining warm anomalies are due in part to the resurgence of the easterly Trade Winds advecting colder waters from east to west, and a return of the sub-surface ocean structure toward more average conditions. Over the last week, large-scale westerly wind anomalies in the western Pacific have appeared again. These will likely lead to eastward advection of warm SSTs to the east, as well as create positive temperature anomalies in the equatorial subsurface ocean. Both these factors would help to prolong the current El Niño conditions for another month or two.Most of the models indicate a slow decline of El Niño conditions, reaching ENSO-neutral conditions by mid-2007. Out of a large set of dynamical and statistical forecast models, the majority predict the current El Niño to continue through March/April 2007. Overall, based on model forecasts and current observations of the ocean surface and subsurface, the probability of a La Niña is less than the climatologically expected odds of 25% throughout the forecast period. The probability of maintaining El Niño conditions through the next couple months is approximately 85%, declining rapidly thereafter. The probability of returning to neutral conditions becomes most likely by mid-2007. Note 1 - Only models that produce a new ENSO forecast every month are included in the above statement.
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