Island Climate Update 264 - September 2022

The NINO3.4 Index anomaly (in the central equatorial Pacific) over the last month (through 31 August) was -1.00˚C (climatology: 1991-2020), showing a strong cooling trend compared to July. In the last four decades, only four Augusts had cooler central equatorial Pacific SSTs than 2022, including August 2010, 1999, 1998, and 1988.

The provisional August monthly SOI was +1.3 and +1.7 from June-August (climatology: 1991-2020), both in the La Niña range.

Trade winds across the central equatorial Pacific were much stronger than normal during August by as much 10-15 knots, like July. This fostered the restrengthening of oceanic La Niña. Strong to very strong trade winds are predicted to continue during spring with a high likelihood for cooling seas.

In the subsurface central equatorial Pacific, substantially cooler than average waters (-3˚C to -5˚C) persisted and expanded eastward. These cooler waters are expected to migrate toward the surface over the next month or two, leading to further decreases in SSTs. Oceanic La Niña will likely grow stronger by late spring.

Taking these factors into account, La Niña conditions are very likely to continue during SeptemberNovember (75-80% chance). During December-February, there is a 55-60% chance for La Niña. A “triple dip” La Niña (three consecutive La Niña events from 2020-2022) is very likely, the first since 1998-2000. It is worth noting that tropical weather patterns during winter 2022 showed relatively strong similarities with those of 1998.

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