Island Climate Update 244 - January 2021

The NINO3.4 Index anomaly (in the central Pacific) for the last month (through the 3 rd of January) was 0.84˚C, increasing from 1.03˚C from last month. This likely means that the oceanic La Niña has peaked however, La Niña’s influence on the atmosphere is expected to last for months to come. Overall, below average SSTs continued in the central Pacific, consistent with a non traditional central Pacific (i.e. Modoki ) La Niña.

During December, the Madden Julian Oscillation (MJO) was active over the Maritime Continent, extending into the West Pacific and associated with the development of two tropical cyclones, Yasa and Zazu , and some flooding rainfall in the Southwest Pacific. In January, MJO activity is favoured over the Indian Ocean. This is because of persistently warmer than average ocean waters across the Indian Ocean and the non traditional style of La Niña.

Tropical cyclone development is unlikely in the Southwest Pacific over the next several weeks, but the MJO may reach the basin by the end of the month, increasing the chance for development and associated heavy rainfall for some island groups.

In December, the South Pacific Convergence Zone was displaced northeast of its climatological position, atypical of La Niña. For high islands, the potential for landslides and river flooding is higher than normal this wet season in the off equatorial South Pacific (New Caledonia, Vanuatu, Fiji, Tonga, Niue, and southern Cook Islands) due to the expected wetter than normal conditions.

Based on the consensus from international models, the probability for the continuation of La Niña is 92% for January March. During April June, ENSO neutral becomes most likely at 66%.

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