The latest forecasts from the WMO Global Producing Centers for seasonal predictions indicate that sea surface temperatures in the equatorial Pacific are expected to remain close to average, with a 70% chance of ENSO-neutral conditions continuing and a 30% chance of La Niña conditions developing during the period June–August 2025.
Forecasts for the period July–September 2025 suggest about a 65% chance of continued ENSO-neutral conditions, with the chance of La Niña conditions slightly increasing to about 35%. The chances of El Niño developing are negligible during the forecast period (June–September).
It is an arduous task to configure implications of the 30–35% La Niña component. Overwhelming ENSO-neutral conditions, coupled with neutral or near-negative-neutral IOD through the monsoon, may steer the seasonal rainfall somewhere in the normal range. Deviations, if any, will have to be attributed to the complex interplay of other factors driving monsoon circulation.
ENSO: As of May-end, both ocean and atmospheric indicators reflect ENSO-neutral conditions, with sea surface temperatures remaining close to average across the equatorial Pacific. However, there are aspects needing due consideration and deliberation before arriving at a logical outcome. One: the intra-seasonal variability in the atmosphere, which is often related to the Madden–Julian Oscillation (MJO), can significantly impact surface and sub-surface conditions across the Pacific Ocean. And two: considering the well-known “spring predictability barrier,” the ENSO forecasts made at this time of the year have lower skill than those made during other periods. Therefore, the state of ENSO needs to be monitored closely and changes, if any, judiciously factored into the updated outlooks.
As on expected lines, there are only marginal changes in the Nino indices across the equatorial Pacific Ocean. After the dilution of La Niña conditions in Feb 2025, Nino 3.4, the marker index of ONI, was fluctuating between +/- 0.1°C for the last three months. Water has a long memory, and the SST in the Nino region is likely to stay within the threshold mark of +/- 0.5°C for the monsoon season.
IOD: Sea surface temperature variability in the tropics can significantly impact the global climate through atmospheric circulation. IOD events significantly influence climate conditions in Southeast Asia, East Asia, and in and around the Indian Ocean. IOD and ENSO have some permutations and combinations which impact the Indian monsoon effectively. But ENSO-neutral and IOD-neutral combination is least studied and has a limited role in driving the monsoon current. IOD is likely to remain neutral this monsoon season. The IOD index for the week ending 08 June 2025 was -0.17°C. After staying in the positive domain since Feb 2025, the index has dropped below 0°C. This is consistent with 7 of 8 international models assessed, which also forecast a negative pattern developing at some point between June and September. This could be a temporary change, and the index may once again become marginally positive during the next few weeks.
MJO: The latest observations indicate the MJO to come out of the meandering phase and get reorganized in the coming weeks. The ECMWF remains more bullish for the forecast. MJO is favoured to propagate eastward in the Western Hemisphere. In the Eastern Hemisphere, medium-range ECMWF probabilistic guidance shows increases in the TC genesis signals centered over the Bay of Bengal and over the northern South China Sea. However, in consideration of the TC climatology tapering off by mid-June in the northern Indian Ocean due to monsoonal shearing, no Tropical Cyclone shapes are likely. However, in the South China Sea, where the environment looks to be more congenial for development—subject to MJO staying more coherent during week 3—this would favour below-normal odds for tropical cyclone formation in the Western Pacific. Any of these storms forming in the South China Sea at this point of time do influence the southwest monsoon stream over the Indian subcontinent.
After the initial acceleration, the monsoon current had weakened. In the first ten days of the month, the rains were largely scanty. The pan-India shortfall between 01 and 10 June was 33%. However, promising conditions are building up to revitalize the monsoon and take it deeper too, over the hinterland of eastern and central parts.
