Island Climate Update 271 - May 2023

The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the beginning of May was 0.21˚C, in the neutral range, but gradually warming..

The SOI was neutral (0.1) during April and +0.3 from February-April.

Trade winds once again relaxed during mid-to-late April, particularly in eastern parts of the equatorial Pacific, owing to a pulse of the Madden-Julian Oscillation (MJO). The result was continued warming of SSTs and higher than average sea surface heights in the east of the basin.

In the sub-surface equatorial Pacific, warming continued to occur, with the most dramatic warming occurring east of the dateline. Some areas warmed by 2˚C, while subsurface temperatures in the east of the basin are now over 3˚C above average (+4˚C from the latest weekly value). This was due to a downwelling Kelvin wave continuing to progress eastwards and a strengthening of the coastal El Niño off Peru.

NIWA’s analysis indicates that El Niño has a 70-80% chance of developing during winter and continuing through spring. Meanwhile, ENSO-neutral conditions have a 30% chance of continuing through July.

The changes observed to the equatorial Pacific during April, as described above, support a continued progression toward El Niño thresholds. Anomalous warmth is building in the surface and subsurface of the equatorial Pacific Ocean, there is a reduction of trade winds across the basin, and there is an expectation for these conditions to continue. An ‘El Niño Watch’ status remains in place.

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Island Climate Update May 2023 [PDF 5.4 MB]