The ocean and atmosphere have transitioned to a weak La Niña that will likely be brief, primarily focused on the central Pacific (i.e., La Niña “Modoki”). There is a 50% chance that La Niña will continue during February-April 2025.
As of 19 January, the 30-day NINO3.4 Index (in the central equatorial Pacific) was -0.76˚C, slightly in the La Niña range. The 30-day relative Niño 3.4 Index (RONI) was -1.31˚C, reflective of the central equatorial Pacific being significantly cooler than the average of the global tropics.
The Southern Oscillation Index (SOI) was on the La Niña side of the neutral range during November-January (+0.4), while the January value was -0.2 (in the neutral range).
The subsurface equatorial Pacific is 2˚C to 4˚C cooler than average just below the surface in the east of the basin.
Above average upper oceanic heat content continues in western parts of the Pacific basin, which is also a La Niña signature.
The South Pacific Convergence Zone (SPCZ) was located slightly south of its climatological normal position during January.
During February-April, model guidance favours an enhancement in convective forcing over the western Pacific and Maritime Continent, consistent with La Niña-like patterns. This may lead to enhanced rainfall for some island groups such as Palau, Guam, Northern Marianas, Federated States of Micronesia, Marshall Islands, and southern Papua New Guinea east to Niue (see pages 6-7 for more information).
Tropical cyclone season continues through April 2025. While no activity is forecast in the short-term, tropical cyclone chances may increase from early February as a pulse of the Madden-Julian Oscillation (MJO) is expected to move through the western Pacific Ocean.
