Island Climate Update 238 - July 2020

During June, the NINO3.4 Index anomaly (in the central Pacific) was 0.12˚C. Upper oceanic heat content decreased notably across the east central equatorial Pacific. Anomalies were below average east of the International Dateline, suggestive of an ocean system that is moving towards La Niña. 

In the subsurface ocean, cooler than average conditions pushed eastward during June with widespread anomalies of 0.5˚C to 2.0˚C. Warmth increased slightly at depth in the western Pacific. At this stage, the anomalies are consistent with developing oceanic La Niña conditions. 

Rainfall and convection was below normal across the equatorial Pacific during June, consistent with the cooling trend in the ocean. 

Trade winds during June were stronger than normal in the east central Pacific. This is expected to continue over the next 1 3 months and could lead to more cooling in the eastern and/or central Pacific. 

According to the consensus from international models, ENSO neutral and La Nina conditions are about equally likely (51% and 47% chance, respectively) for the July September period. For the October December and January March 2021 periods respectively, the probability for ENSO neutral conditions is 42% and 53%. The probability for La Niña is 45% during October December and 34% in January March. 

Based on the observations and forecast guidance, a La Niña watch is in place as of June 2020.

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