Temperature Anomaly Grow Big: El Nino Become Very Strong

Key Takeaways:

• Niño 3.4 climbed to 2°C on 14th September 2026, indicating a very strong El Niño signal.
• Niño 4 dropped to -0.1°C, while warming remains concentrated farther east across the equatorial Pacific.
• The IOD index reached +0.65°C, although a sustained positive IOD is yet to be firmly established.
• A system moving from Thailand and Myanmar may enter the Andaman Sea and could potentially develop into the first cyclonic storm of the year.
• Forecast Validity: Until Next Update

The complex El Niño weather pattern that builds chaotic climatic conditions is still unfolding in the Central and Eastern Equatorial Pacific Ocean. These conditions lead to disastrous heavy rainfall in some pockets and harsh droughts in a few countries around the Pacific, from Peru to Indonesia and Australia. The vulnerable pockets for drought include the countries of Central America and countries around the Pacific Ocean. Extreme rainfall gets triggered in the Horn of Africa, the Western United States, and the Pacific Coast of South America.

Numerical models use an algorithm that draws on the analysis of links between changing air temperatures at a network of grid points across the Pacific region and could predict an El Niño event at least a year ahead. Conventional methods are unable to make reliable El Niño forecasts six months in advance. So, the warning time nearly gets doubled, though the confidence and reliability at the extreme end of the forecast still remain low. Work is going on to adapt the algorithm to be able to predict the precise timing and peak strength of the event.

The ongoing El Niño event is forecast to reach unprecedented strength. That, embedded with the influence of global warming, would mean that the effects of this event look different from the strong El Niños of the past. There are some other aspects also that make this year unique, such as El Niño having strengthened earlier than it did during previous strong events, such as those that occurred in 1997 and 2015.

Indonesia has seen an above-average start to the wildfire season. Meanwhile, with the season reaching its fag end, Indonesia has had lower-than-average monsoon rainfall, even as flooding has hit some parts of the country—an expected effect of El Niño. In parts of Southern and East Africa, dry weather combined with high prices for fuel and fertilizers means tens of millions of people in these regions may experience acute food insecurity due to the El Niño event.

ENSO: No two El Niño events are the same. Pacific warming with respect to Niño indices is monitored over about 15 million square kilometres. Warming is not uniform at all, and pockets of warming have a strong and consequential impact on different parts of the globe. Warming over the Central Pacific will have a different impact from warming over the Eastern Equatorial Pacific.

The effects of each El Niño event vary depending upon intensity, duration, timing, and also its interaction with other climate variability modes like IOD, MJO, etc. The process is so complex that even when ENSO is neutral, extreme weather can still occur, says WMO. WMO classifies ENSO events as weak, moderate, strong, and very strong. The term ‘Super El Niño’ is not part of WMO’s operational classification system and is therefore not used in official WMO products.

Since mid-April 2026, above-average equatorial SSTs have increased across the East-Central and Eastern Pacific Ocean. Niño 3.4, the marker index for El Niño, has reached the threshold of a very strong El Niño. The index value, after being stagnant at 1.8°C for the last five weeks, climbed to 2°C on 14th September 2026. The Niño 4 index at the extreme western end of the Niño region plunged to -0.1°C, going below the zero mark for the first time, a rare feat. This usually happens during ‘Canonical’ El Niño events.

IOD: After staying in the neutral range for four weeks, the index is back above the positive IOD threshold (+0.4°C). The index value for the week ending 13th September 2026 was +0.65°C. But this one observation cannot be construed as indicating that a positive IOD is underway soon. Models suggest that a positive IOD is likely to develop during the autumn of the Northern Hemisphere, but there is still uncertainty about its strength and duration.

MJO: Overshadowed by the El Niño background state, the MJO has continued propagating eastward from the Western Hemisphere into the Indian Ocean. The amplitude remained confined to the inner circle during the previous week. Models are predicting a return to the Western Hemisphere yet again during the last week of September 2026. However, the MJO pulse may still remain incoherent, fighting a much stronger and stationary ENSO signal.

The rain-deficit monsoon season may end on a stormy note. The first cyclone of this year, from the remnants of a weather system moving across Thailand and Myanmar, may enter the Andaman Sea and develop into a cyclonic storm. MJO may provide symbolic support for cyclogenesis over the Bay of Bengal.