MJO May Trigger First Cyclone of Post Monsoon Over Bay of Bengal

Key Takeaways:

• Strong El Niño conditions: Exceptional warming across the equatorial Pacific is raising concerns about India's winter weather, agriculture and water resources.
• Extreme Pacific temperatures: The supplied analysis reports Niño 3 anomalies reaching +3.5°C and subsurface warming of up to 8°C in some regions.
• Positive IOD development: The Indian Ocean Dipole index reportedly remained at +0.88°C for the week ending October 18, with a positive event potentially developing.
• Bay of Bengal cyclone risk: An approaching MJO pulse may support cyclonic development during the final week of October, threatening coastal areas from Tamil Nadu to West Bengal.
• Forecast Validity: Until next update.

El Niño impaired the Indian summer monsoon, plunging more than half of the country into despair and leaving it still struggling to bear the agricultural losses.

Now, India is heading into winter under the worrying shadow of a very strong El Niño, which could turn out to be the strongest event ever. Its peak is yet to arrive. Concerns are extending beyond temperature and rainfall to agriculture, dipping water tables, drying water bodies, exhausting water reserves and rupturing supply-chain management.

El Niño develops when trade winds weaken and warm water spreads eastwards, allowing heat to accumulate, more dominantly over the central and eastern equatorial Pacific Ocean. Planet Earth has been painted red with extreme heat, and the hot spots leave anxious moments for some pockets that may bear temperatures higher than during any prior El Niño event on record. August 2026 was the joint-hottest month ever recorded globally, matching July 2023, with temperatures 1.65°C above pre-industrial levels. The global temperature in September 2026 was 1.63°C above pre-industrial levels and marked the second consecutive month in 2026 to cross the 1.5°C mark. September 2026 was also the world's second-hottest September on record, leaving enormous worries for the months to come. These developments are sounding a clarion call and highlighting the growing risks of a warming planet as countries prepare for the UN Climate Summit, COP31, scheduled to be held in Antalya, Türkiye, from November 9 to 20, 2026.

ENSO: The core Niño 3.4 index region shows sea surface temperature anomalies running from +2.5°C to +3.7°C above normal, marking some of the highest recorded surface heat levels in modern history.

A massive 9,000-mile-long warm-water mass moving across the Pacific has brought subsurface temperatures up to 7.5°C to 8°C warmer than average in specific pockets. Scientifically, at this juncture, such explosive warming of the equatorial Pacific has nearly become inexplicable. What triggers initiate it and how it gets neutralised in the times to come remain mysterious. The damaging implications will leave a trail of destruction on many counts across the globe.

Above-average SSTs increased across the east-central and eastern equatorial Pacific Ocean, while below-average SSTs were quite evident near and west of the Date Line. While the Niño 3.4 and Niño 1+2 indices retained their temperature anomalies this week, Niño 4, the farthest index in the central Pacific, turned negative yet again. The Niño 3 temperature anomaly marginally rose from 3.4°C to 3.5°C. The Niño 3 region has apparently recorded its highest temperature anomaly ever. Earlier, the highest value during El Niño 2015–16 was 3.1°C on November 23, 2015, and during El Niño 2023–24, it touched 2.3°C on August 28 and November 27, 2023.

IOD: The IOD is neutral, but the positive phase of the IOD continues. The Western Indian Ocean (near East Africa) is quite warmer than normal, while the eastern shore, next to Indonesia and Australia, is cooler. Stronger-than-normal winds are pushing the warm waters away from that region. This is the sixth consecutive week that the index has exceeded the positive IOD threshold (+0.4°C). Two more weeks of this pattern will establish the positive IOD event of this season. The index value for the week ending October 18, 2026, was +0.88°C, the same as last week. Models indicate the development of a positive IOD in the coming weeks, albeit with some uncertainty about the strength and duration of the event.

MJO: Strong El Niño conditions continue to overshadow any coherent MJO activity over the global tropics. The MJO pulse is favoured to reach the Indian Ocean in phases 2 and 3. It is still struggling to come out of the inner circle and build a decent amplitude. The forecast position of the MJO over the Indian Ocean may provide support for developing stormy conditions over the Bay of Bengal.

With support from the MJO, a cyclonic storm is likely to develop over the Bay of Bengal–Andaman Sea axis. This will be the maiden storm of this post-monsoon season. The east coast from Tamil Nadu to West Bengal, across Andhra Pradesh and Odisha, will be at risk of hazardous weather conditions during the last week of October.