ENSO-neutral conditions are now in place, and there is a 70% chance that ENSO-neutral conditions will continue during June-August 2025, followed by a 60% chance that ENSO-neutral will remain in place during July-September.
As of 19 May, the 30-day NINO3.4 Index (in the central equatorial Pacific) was -0.02˚C, in the neutral range. The 30-day relative Niño 3.4 Index (RONI) was -0.41˚C, reflective of the central equatorial Pacific being cooler than the average of the global tropics and on the La Niña side of
neutral.
The Southern Oscillation Index (SOI) was on the La Niña side of the neutral range during March-May (+0.5), while the May value was +0.1 (in the neutral range).
The subsurface equatorial Pacific is barely cooler than average just below the surface in the central part of the basin, a continued warming trend since last month. In addition, above average temperatures are emerging in the eastern Pacific. Both of these factors indicate ENSO-neutral conditions. Meanwhile, above average upper oceanic heat content continues in western parts of the Pacific basin.
The South Pacific Convergence Zone (SPCZ) was located close to its climatological normal position during May.
During June-August, model guidance favours an enhancement in convective forcing over the western Pacific and Melanesia, collocated with the warmest sea surface temperatures and position of the SPCZ. This may lead to enhanced rainfall for places such as southern Papua New Guinea and the Solomon Islands in particular.
However, drier than normal conditions are likely to occur for several island groups along and north of the equator, including the Federated States of Micronesia, the Marshall Islands, Nauru, and portions of Kiribati (see pages 6-7 for more information).
