El Nino May Arrive Earlier Than Expected: Monsoon Risk Grows

Key Takeaways:

• La Niña has ended, and ENSO-neutral conditions are currently prevailing.
• El Niño is likely to develop between May and July 2026 and persist through the year.
• Strong El Niño may increase global temperatures, pushing 2026 towards record heat.
• Indian monsoon could face risks, though IOD evolution will be a key factor.

La Niña conditions have faded completely, and an ENSO-neutral phase has started. Consequently, the Climate Prediction Center (CPC) has issued a notice of ‘El Niño Watch’. As of end-April 2026, the equatorial Pacific is in an ENSO-neutral state. The latest CPC forecast gives an 80% chance of ENSO-neutral conditions being favoured through April–June 2026. El Niño is likely to emerge in May–July 2026, with a 61% chance, and persist at least through the end of 2026. Earlier, the forecast had preferred the emergence of El Niño halfway through the monsoon and its impact on the seasonal rains, more adversely in Aug–Sep 2026. The IRI ENSO plume forecast has given a 70% chance of El Niño developing in Apr–Jun 2026, versus 30% for continued neutrality, with El Niño remaining a dominant category through the rest of 2026 at high probabilities of 88–94%.

Strong El Niño conditions could push 2026 towards record global heat. Despite cooling La Niña conditions at the start of 2026, the emergence of a strong El Niño may increase the risk of 2026 becoming the hottest year. Climate researchers expect 2026 to rank among the hottest years ever recorded, with an incremental rise in global temperatures as the year progresses. As per scientific data, the first quarter of 2026 already ranks as the fourth warmest on record, even though the cooling La Niña had a mitigating effect.

More often, El Niño has not been kind to the Indian monsoon. It has corrupted seasonal rainfall eight out of ten times. Records vindicate that there are very few exceptions, like 1997, when rainfall exceeded the seasonal average amidst strong El Niño conditions. Truly speaking, a strong positive IOD was the saviour, which effectively offset the ruinous part of El Niño. Sturdy evidence of a very powerful El Niño is emerging, but the prediction of IOD will be more reliable when closer to the event. A lead time of more than four weeks reduces the confidence level substantially.

ENSO: The sub-surface warming in the ocean precedes the heating of the sea surface on account of evolving El Niño. The measurable manifestation in the top layer gets realized much after deep-section warming. The La Niña phase has just got over. The neutral phase is likely to have a short stint and is unlikely to last beyond the Apr–Jun 2026 quarter. Caution is advised in interpreting these probabilities due to differing biases and performance of different models. At longer leads, the skill of the models degrades due to varying initial conditions and differing model physics.

The observed SST anomaly in the Niño 3.4 region during the Jan–Mar 2026 season was -0.25°C, and for March 2026, it was +0.03°C. The most recent monthly average of Niño 3.4 for Apr 2026 was -0.05°C. The latest value of Niño 3.4 for the week ending 27th Apr 2026 was +0.2°C. These values indicate that Pacific sea surface temperatures are in an ENSO-neutral state and are beginning to develop into El Niño. To qualify for El Niño, the monthly SST anomaly in the Niño 3.4 region (5°S–5°N; 170°W–120°W) must exceed 0.5°C.

IOD: The Indian Ocean Dipole value has been maintained close to zero for the last about six weeks. The index value for the week ending 26 Apr 2026 was +0.09°C. The IOD is considered inactive when the DMI lies between -0.4°C and +0.4°C. Traditionally, El Niño events are accompanied by neutral or positive IOD. Conversely, La Niña events are escorted by negative IOD. A strong positive IOD event was last noticed during El Niño of 2023, and it spilled over to the start of 2024 as well. The IOD has remained neutral or negative since May 2024. The index had turned strongly negative between Aug–Nov 2025. The first quarter of 2026 showed indications of a positive IOD event but collapsed after mid-March 2026.

MJO: Dynamical models are in agreement, favouring continued MJO activity over the Indian Ocean, but generally indicate a rapid drop in signal strength as the MJO moves into the Maritime Continent during the first half of May 2026. The MJO has propagated eastward with minimal amplitude, and the pulse is majorly confined to the inner circle in Phases 1 and 2. It is unlikely to come out in the first half of May 2026. It may not be of any help in building up the cross-equatorial flow over the Andaman Sea as a precursor to the southwest monsoon. A typical monsoon onset is often associated with the arrival of the wet phase of the tropical MJO over the Indian Ocean, likely due to the promotion by the MJO-initiated eastward propagating westerly wind anomaly.

The onset phase of the monsoon over the Andaman Sea is drawing closer. Last year, the monsoon stream arrived on 13th May and quickly moved to the North Andaman Sea by 17–18 May 2025. This season, MJO is unlikely to accentuate the equatorial flow over that region between the 2nd and 3rd week of May 2026.