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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 August 2009SummaryThe equatorial Pacific is maintaining weak El Niño levels. During the Aug-Oct season there is an approximately 85% probability of maintaining at least weak El Niño conditions, and a 14% probability of returning to ENSO-neutral conditions. Probabilities for El Niño remain near 80% for most of the remainder of 2009, decreasing to 70-75% in early 2010 and fall below 50% during northern spring 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 have shown weak signs of El
Niño, including wind and convection patterns, but these are
presently not significant. In June and July, sub-surface temperatures
were above-average over a
large portion of the equatorial Pacific, suggesting the possibility for
further development of the oceanic aspects of El Niño. However,
since mid-July temperatures at the surface and sub-surface have
weakened. While El Nino conditions are still likely to persist through
the end of the year, it is possible that they may not strengthen
further. Reinforcement by westerly wind anomalies in the western and
central Pacific will be necessary to increase the positive SST
anomalies, which could then provide an opportunity for further
atmosphere-ocean
coupling during the coming several months. |
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