Island Climate Update 280 - February 2024
El Niño continued during January and has around a 100% chance of persisting through to April.
The monthly NINO3.4 Index anomaly (in the central equatorial Pacific) at the end of January was +1.79˚C, within the range of a strong El Niño (classified when the NINO3.4 Index is greater than +1.5˚C). Although the current El Niño event is past its peak oceanic intensity, atmospheric patterns will likely continue to show El Niño-like tendencies in the months ahead.
The Southern Oscillation Index (SOI) was in the neutral range during January (+0.3) and during November-January (-0.4). This suggests that El Niño’s reflection in the atmosphere has been atypical, particularly considering the oceanic intensity.
Trade wind strength was near normal or above normal during January which resulted in a weakening of the oceanic El Niño. However, a major reversal is taking place, with a westerly wind event occurring near the equator and off the equator in the South Pacific. This will likely give the ocean-atmosphere system an El Niño-like ‘jolt’, slowing El Niño’s decay.
This feature’s influence will then ease during March, likely causing El Niño to weaken further.
The subsurface equatorial Pacific is cooler than average across much of the basin below 100 metres depth and the west Pacific is 0.5˚C to 1.5˚C below average near and west of the International Date Line. The east remains warmer than average, with the basin now showing more of a traditional El Niño-like signature, despite the El Niño event now being in its decay stage.
A marine heatwave is active between New Caledonia and Fiji, extending eastward to Samoa and the northern Cook Islands. The SPCZ is forecast to be very active during February and will likely contribute to several tropical cyclones, such as Nat and Osai, which both formed in the eastern part of the basin near the northern Cook Islands early in the month. The risk for tropical cyclone activity is often higher in the eastern portion of the basin during El Niño.
All islands should remain vigilant, as tropical cyclone season continues through to April.
Island Climate Update - Jan 2023 [PDF 6MB]