Global Seasonal Climate Update for April-May-June 2026

Outlook for Oceanic Drivers for the Next Season: For the forecast period beyond April 2026, the Niño 3.4 plume shows an exceptionally tight consensus for a rapid transition into El Niño territory by May, with several models suggesting the development of a strong El Niño as early as June/July (Fig. 5, left). While the typical "spring predictability barrier" is evident in the increased spreading of the plumes starting in April/May, the upward trajectory remains consistent across nearly all forecast systems.Similarly, the IOD index (Fig. 5, right) indicates a shift from the neutral conditions observed in early 2026 toward a positive IOD phase by mid-year, with most models converging on an index above +0.5°C by July/August. In the Atlantic, both the NTA and STA are expected to maintain their slightly above-average values throughout the forecast period.