Island Climate Update 239 - August 2020

During July, the NINO3.4 Index anomaly (in the central Pacific) was +0.04˚C. The NINO 1+2 Index (eastern Pacific) was 0.72 C, decreasing from 0.57 C in June. Upper oceanic heat content remained lower than normal over the far eastern Pacific with marginally above normal upper oceanic heat content persisting west of the Date Line. Overall, the pattern remains reflective of developing La Niña conditions. This will continue to generate an atmospheric response, with suppressed rainfall and convection about the equatorial Pacific. 

Trade winds during July were stronger than normal in the central Pacific and slightly reduced over the eastern Pacific. Over the coming weeks, trade winds are forecast to continue in a similar fashion, supporting the continuation of the current SST distribution; warmer than average in the west and cooler than average in the east. 

Rainfall and convection continued to be below normal across much of the equatorial Pacific during July, consistent with the evolution of ocean temperatures. Rainfall was above normal across Indonesia and the Maritime Continent, also in keeping with a developing La Niña state. 

Based on the consensus from international models, the probability for La Niña conditions is 52% for the August October period. For the November 2020 January 2021 and February April 2021 periods, the probability for La Niña is 49% and 27%, respectively. The probability for ENSO neutral conditions increases to 63% during February April 2021.

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