Island Climate Update 242 - November 2020

During October, the NINO3.4 Index anomaly (central Pacific) was 0.86˚C. The NINO 1+2 Index (eastern Pacific) was 0.56 C. Upper oceanic heat content continued to decrease in the east central part of the Pacific basin. Heat content continued to be higher than normal in the western Pacific. Overall, the pattern is consistent with La Niña conditions.

Trade winds during October continued to be stronger than normal across the equatorial Pacific, causing additional cooling of the sea surface in the west central part of the basin. Trade winds are expected to continue to be stronger than normal, particularly in the west central Pacific (e.g. Kiribati, Nauru), into austral summer. This will encourage additional cooling of SSTs with La Niña experiencing a peak in December or January.

Rainfall and convection were well below normal in the west central Pacific, near and west of the International Dateline, during October. The South Pacific Convergence Zone was displaced to the south, consistent with La Niña. The potential for landslides and river flooding is higher than normal this coming wet season in the off equatorial South Pacific, especially when a tropical disturbance follows a prolonged period of wetter than normal conditions.

Based on the consensus from international models, the probability for La Niña conditions is 96% for the November 2020 January 2021 period. For the February April 2021 period, the probability for La Niña is 59% and 40% for ENSO neutral conditions.

Based on the observations and forecast guidance, La Niña conditions have been met.

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