Island Climate Update 223 - April 2019

Warmer than average sea surface temperatures (SSTs) now cover the tropical Pacific uniformly, a sign of a strengthening oceanic El Niño event.

While the flavour of El Niño has been closer to the central-based type over the last month or two, the eastward propagation of anomalously warm ocean water may signal that the event is transitioning to an east-based one. This transition could bring more traditional El Niño impacts for the Pacific Islands, such as increased rainfall for northern and eastern island groups and reduced rainfall for western and southwestern island groups.

The NINO3.4 index SST anomaly for March was +0.81°C, an increase of 0.38°C compared to February 2019. The atmosphere continued to respond to a warm pool of water in the central and western tropical Pacific Ocean. This was reflected by above normal rainfall and cloud cover across the region.

The Southern Oscillation Index (SOI) was negative during March (-0.7), although not as persistently negative as in February. The conventional threshold for El Niño (SOI values below -1.0 for three consecutive months) has not been reached, but a weakly coupled central-based El Niño remains present.

According to the consensus from international models, the probabilityfor oceanic El Niño conditions is 90% for the April-June period. Beyond this, for the July to September period, the probability for oceanic El Niño conditions increased to 73%, up from 55% last month. This continues to suggest the potential for a ‘protracted’ event (multi-year duration).

Download the full report: Island Climate Update April 2019 [615KB PDF]