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ENSO Quick
Look IRI ENSO Update / Forecast Technical ENSO Update IRI Probabilistic ENSO Forecast ENSO Prediction Plume Monthly archive ENSO Update21 May 2009SummaryThe equatorial Pacific has warmed to the positive half of the neutral range, after weak La Niña conditions ended early last month. During the May-Jul season there is an approximately 75% probability of maintaining ENSO-neutral conditions. However, by Jul-Sep season and enduring through the end of 2009, the probability for El Niño conditions rises to 45%, for neutral conditions decreases to 45 to 50%, and for a return to La Niña conditions only 5 to 10%.General Discussion
Weak La Niña conditions that were observed from December 2008
dissipated in early April. ENSO-neutral conditions, as indicated by
the NINO3.4 SST anomaly index, have prevailed during April and continue
through the present, and the index has recently moved into the warm half of
the neutral range. Characteristics of La Niña in the atmospheric
anomalies have continued longer than those of SST, although during May these
have also returned toward more neutral conditions. The question of whether or not
La Niña conditions might continue into northern summer, or re-emerge
during northern autumn, is lately shifting toward the question of whether or
not neutral conditions will continue through the end of the calendar year, as
opposed to possible development of El Niño conditions during northern
summer or autumn. |
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