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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update20 December 2006SummaryAs of mid-December sea surface temperatures (SSTs) remain over 1.0C above average throughout much of the equatorial Pacific, exceeding 1.5C in the central and eastern equatorial Pacific. El Niño conditions have been in effect since mid-September. Based on the latest observations and forecasts, the probability of maintaining El Niño conditions through the December-January-February 2006/07 season is approximately 95%.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, but are still greater than 1.5C above average. The initial increase of SSTs in mid-2006 was due largely to persistent westerly wind anomalies over the west Pacific. The westerly wind anomalies were particularly strong and large scale during September and October, and this is when the temperature anomalies at and below the surface evolved most rapidly. The subsurface anomalies extend from the dateline to the eastern Pacific, with maximum subsurface temperature anomalies exceeding 4.0C, associated with greater than 35m downward perturbation to the thermocline. These thermocline anomalies will maintain, or possibly further increase, SSTs as they are brought to the surface in the eastern Pacific by the local upwelling currents. Also associated with the westerly wind anomalies, the western Pacific thermocline has shoaled in recent months. Those thermocline anomalies, and associated cool sub-surface temperature anomalies, are now propagating eastward along the equator. They are anticipated to erode the current El Niño conditions in the early part of 2007.The observations and models have been retaining their concensus of El Niño conditions persisting through the first several months of 2007. Out of a large set of dynamical and statistical forecast models, nearly all predict El Niño through early 2007. Overall, based on model forecasts and current observations of the ocean surface and subsurface, the probability of a La Niña is much less than the climatologically expected odds of 25% throughout the forecast period. The probability of maintaining El Niño conditions through the next several months is approximately 95%, and the probability of returning to neutral conditions during that time is less than 10%. Note 1 - Only models that produce a new ENSO forecast every month are included in the above statement.
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