Source: National Weather Service

The majority of models now predict La Nina conditions to develop during June-August and to continue through early 2011, according to the Climate Prediction Center of the National Weather Service. Confidence in this outcome is reinforced by the recent performance of the NCEP Climate Forecast System (CFS), the large reservoir of colder-than-average subsurface water and signs of coupling with the atmospheric circulation. Therefore, La Nina conditions are likely to develop during July-August 2010.

During June 2010, sea surface temperature (SST) anomalies continued to decrease across the equatorial Pacific Ocean, with negative anomalies expanding across the central and eastern Pacific. While the rate of decrease slowed during June, all of the Nino indices were cooler compared to the previous month. The subsurface heat content (average temperatures in the upper 300m of the ocean) also remained below-average during the month. Subsurface temperature anomalies became increasingly negative in the east-central equatorial Pacific and extended to the surface across the eastern half of the basin. Also during June, enhanced convection persisted over Indonesia, while the area of suppressed convection strengthened and expanded westward over the western and central equatorial Pacific. Enhanced low-level easterly trade winds and anomalous upper-level westerly winds prevailed over the western and central equatorial Pacific. Collectively, these oceanic and atmospheric anomalies reflect developing La Nina conditions.

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