El Niño has continued to weaken during May, and ENSO neutral conditions are favoured to develop by June 2024.
The 30-day NINO3.4 Index anomaly (in the central equatorial Pacific) as of 20 May was +0.49˚C, falling below the El Niño threshold of +0.7˚C.
The 30-day Niño 1+2 Index anomaly was -0.22˚C, within the neutral range. In fact, it is the lowest value in that region since February 2023, at the end of the last La Niña event.
The Southern Oscillation Index (SOI) was in the neutral range during March-May (+0.2), but the May value was +0.7 (in the La Niña range).
Periods of enhanced trade winds in the coming months should contribute to additional cooling of sea-surface temperatures near the equator.
During mid-May, the subsurface equatorial Pacific was 4˚C to 6˚C cooler than average just below the surface in the east of the basin.
Meanwhile, above average temperatures persisted in the central and western parts of the basin. This signature was reflective of an oceanic transition out of El Niño toward a possible La Niña in a few months.
The South Pacific Convergence Zone was near its climatological normal position during May.
During the first half of June, a pulse of the Madden-Julian Oscillation may propagate across the Pacific. This may lead to a period of heavy rainfall with the potential for flooding, especially south of the equator in the South Pacific, like what’s shown on page 6 (June outlook).
