ENSO-neutral conditions remain in place, and there is a 70% chance that ENSO-neutral conditions will continue during July-September 2025, followed by a 60% chance that ENSO-neutral will remain in place during August-October.
As of 22 June, the 30-day NINO3.4 Index (in the central equatorial Pacific) was +0.01˚C, in the neutral range. The 30-day relative Niño 3.4 Index (RONI) was -0.31˚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 April-June (+0.6), while the June value was +0.5 (on the La Niña side of the neutral range).
Temperatures in the subsurface equatorial Pacific are generally near average just below the surface across most of the basin, a continued warming trend since last month. Upper oceanic heat content showed some cooling in the western Pacific during June while the eastern Pacific showed some warming. Both of these factors indicate ENSO-neutral conditions.
The South Pacific Convergence Zone (SPCZ) was located close to its climatological normal position during June.
During July-September, 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 from Papua New Guinea east to Fiji and
Tonga.
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, Kiribati, and northern Tuamotu Archipelago (see pages 6-7 for more information)
