Island Climate Update 245 - February 2021

The NINO3.4 Index anomaly (in the central Pacific) during January was 0.81˚C, increasing slightly compared to the previous month. Notably, the most unusually cool SSTs were located in the west central equatorial Pacific, consistent with a non traditional central Pacific La Niña, also known as Modoki . While the oceanic La Niña has peaked, the atmospheric expression of La Niña is expected to continue for at least the next three months.

In the subsurface equatorial Pacific, ocean temperatures increased for the second consecutive month in the east. Conversely, in the west central Pacific, the cool pool intensified slightly at depth. This suggests that the trend away from La Niña will be slow rather than abrupt. Enhanced tropical trade winds continued during January and are expected to continue through March this will keep La Niña’s cooler than average sea temperatures in place for several months to come.

The Madden Julian Oscillation (MJO) became active in the western Pacific at the very end of January, resulting in the formation of three tropical cyclones (Ana, Bina, and Lucas). During February, increased convection is expected to continue in the western Pacific. This may cause additional tropical cyclone activity and associated heavy rainfall, storm surge and high winds for some island groups, mainly from Fiji westward to Vanuatu and New Caledonia.

Based on the consensus from international models, the probability for the continuation of La Niña is 70% for February April. During May July, ENSO neutral becomes most likely at 66%.