Island Climate Update 249 - June 2021

The NINO3.4 Index anomaly (in the central Pacific) during May (through the 30th) was -0.11˚C, the smallest anomaly since July 2020. The Southern Oscillation Index (SOI) was +0.5, in the ENSO neutral range.

In the equatorial Pacific, upper-oceanic heat content increased for the third consecutive month, while further warming was observed in the sub-surface, reaffirming an end to La Niña.

According to the consensus from international models, the probability for ENSO neutral conditions is 73% during June to August. For September to November and December to February, the probability for ENSO neutral is 49% and 48%, respectively. There is about a 1-in-3 chance that La Niña redevelops during September to November.

Since ENSO neutral conditions are occurring, the MJO is expected to be a primary mode of climate variability over the coming season.

During May, convective forcing was influenced primarily by the active phase of the Madden-Julian Oscillation (MJO) over Africa and the Indian Ocean, before propagating eastward to end the month. These pulses of the active phase of the MJO resulted in enhanced convection (greater than normal rainfall) for parts of Palau, Federated states of Paula Micronesia, Marshall Islands, New Caledonia, Vanuatu, Fiji, Tonga and the Southern Cook Islands.

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