Island Climate Update 215 - August 2018

El Niño – Southern Oscillation (ENSO) neutral conditions continued across the tropical Pacific during July 2018. Sea surface temperatures (SSTs) in the central equatorial Pacific warmed for the fourth consecutive month and are currently slightly above average. The NINO3.4 is currently positive with a value of + 0.46°C for July 2018.

The subsurface ocean remained warmer than average in the eastern equatorial Pacific during July, but anomalies weakened slightly compared to June. Waters remained 2.0°C above average between approximately 20m and 100m depth east of about 130 °W. Trade winds were very close to normal over most of the tropical Pacific, in contrast with the strong positive anomalies (i.e. weaker trade winds) that were present around the International Dateline during June. The Southern Oscillation Index (SOI) was slightly positive (i.e. on the La Niña side of Neutral) with a preliminary value of +0.2 for July 2018. This is consistent with a general weakening of the El Niño-like signals that emerged over during June 2018.

In summary, despite a continued slow warming of ocean surface temperatures in the central and eastern equatorial Pacific, July 2018 witnessed a slight weakening of the El Niño-like signals that previously emerged in June 2018, notably in the subsurface ocean and in the atmosphere.

The consensus from international models is for the tropical Pacific to transition toward El Niño over the next three-month period (55% chance over August – October 2018). The probability for El Niño conditions increases in to 2019, with a 78% chance for El Niño conditions over the February – April 2019 period. The strength and characteristics of this event – if it eventuates – remain uncertain at this point, but indications so far are that it is unlikely to be in the strong category.

Download the report: Island Climate Update August 2018 [3.2MB PDF]