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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update15 November 2006SummaryAs of mid-November sea surface temperatures (SSTs) are over1.0C above average throughout much of the equatorial Pacific, exceeding 1.5C in the central Pacific and far eastern equatorial Pacific. El Niño conditions have been in effect since mid-September. Note that the full criteria for El Niño conditions includes the provision that the eastern-central Pacific anomalies remain at or above these levels for at least three months, and longer to be considered an El Niño event. Based on the latest observations and forecasts, the probability of maintaining El Niño conditions for November-December-January 2006/07 season is approximately 92%.General DiscussionSince mid-August SSTs in the central and in the eastern equatorial Pacific have been increasing, with temperatures near the dateline and in the east Pacific now greater than 1.5C above average. The initial increase of SSTs was due largely to persistent westerly wind anomalies over the west Pacific during July and August. Westerly wind anomalies picked up again in late September and since have been strong and persistent, currently extending east of the dateline. The equatorial heat content is also above-average and has been slowly increasing since early 2006, relative to the 1970-2001 climatology period. The departures from normal of the sub-surface oceanic temperature field, associated with the increasing heat content, and resulting from the westerly wind anomalies, have developed a large-scale coherent pattern. The subsurface anomalies extend from the dateline to the eastern Pacific, with maximum subsurface temperature anomalies exceeding 4.0C, associated with greater than 30m downward perturbation to the thermocline. These thermocline anomalies have the potential to further increase SSTs as they are brought to the surface in the eastern Pacific by the local upwelling currents. Furthermore, the current westerly wind anomalies should further deepen the thermocline, and that together with the eastward advection of temperatures by the windstress are likely to maintain, if not strengthen, the current SST anomalies.The observations and models have been increasing in their concensus of El Niño development based on the set of forecasts over the last six months. They currently suggest that the El Niño conditions are likely to persist at least through early next year. Out of a large set of dynamical and statistical forecast models, nearly all predict El Niño through the end of 2006. 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%. The probability of maintaining El Niño conditions through the next several seasons is approximately 90%, 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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