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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update17 December 2009SummaryEl Niño conditions remain moderate(+) strength in the equatorial Pacific. For the Dec-Feb season in progress there is an approximately 98% probability of maintaining El Niño conditions. Probabilities for El Niño stay at or above 90% through the Feb-Apr season, decreasing to 55% by Apr-Jun season and to the climatological probability of 25% by the Jul-Sep season.General Discussion
During mid-December 2009, the NINO3.4 SST anomaly index continues at
values indicative of a moderate to nearly strong El Niño category.
Until mid-October, the event had maintanined only a weak magnitude,
but strong and persistent westerly wind anomalies during late September,
and especially October, substantially increased the SST anomalies in the
central and eastern equatorial Pacific. The westerly wind anomalies also
had a substantial impact on the sub-surface ocean, deepening the thermocline.
This led to still further growth, helping to ensure the persistence of the
current event for at least a few more months. The wind anomalies in the western
Pacific reversed for about two weeks during November but have again become
westerly for the most recent few weeks, as a result of the passage of a strong
MJO, or intraseasonal variability. El Niño conditions are expected to
persist at least through February 2010, and likely into part of northern
spring 2010. |
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