Island Climate Update 250 - July 2021

The NINO3.4 Index anomaly (in the central Pacific) during June was 0.18 ̊C, the first time it has been positive since July 2020. The Southern Oscillation Index was +0.4, in the ENSO neutral range.

During June, upper-oceanic heat content remained above average across the Pacific. A slight cooling trend occurred in the central part of the basin and is worth monitoring through the rest of the dry season.

According to the consensus from international models, the probability for ENSO neutral conditions is 72% for July-September. For October-December, ENSO neutral is favouredat 50%, although the chance for the re-emergence of La Niñaincreases to 34% compared to last month when it was 31%.

Since ENSO neutral conditions are still occurring, intraseasonalconvective forcing from the Madden-Julian Oscillation and/or Kelvin waves is expected to be an important mode of climate variability. A pulse of convection is expected to reach the western Pacific between the 15-20th, which could result in more unsettled weather around Fiji, extending to the southeast.

Global climate variability may also be influenced by warmer than average ocean temperatures in the central and eastern equatorial Atlantic, which have culminated in the development of an “Atlantic Niño”. When an Atlantic Niñois active in the dry season, there is a tendency for La Niñato become active during the following wet season.

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