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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update16 September 2009SummaryConditions in the equatorial Pacific remain indicative of a weak-to-moderate El Niño. During the Sep-Nov season there is just under 90% probability of maintaining at least weak El Niño conditions, and a 10% probability of returning to ENSO-neutral conditions. Probabilities for El Niño remain near 85% for most of the remainder of 2009, decreasing thereafter to a climatological probability of 25% by mid-2010.General Discussion
Between mid-June and mid-July 2009, the NINO3.4 SST anomaly index rose
to values indicative of the weak El Niño category, where it has
since persisted. Atmospheric conditions show signs of El
Niño, including westerly wind anomalies in the western Pacific
and convection anomalies near the dateline. The sub-surface
temperatures have
remained above-average over a
large portion of the equatorial Pacific since mid-2009, suggesting the
possibility for
further development of the oceanic aspects of El Niño. Between
July and August, temperatures at the surface and sub-surface weakened,
but wind anomalies in the western Pacific are currently
reinforcing the event. Continuation of these wind anomalies may lead to
further development. Whether the event continues to strengthen or not,
the El Niño conditions are expected to
persist through
the end of the year. |
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