Chennai: The El Nino event developing over the equatorial Pacific is expected to peak between Nov 2026 and Jan 2027, coinciding with the northeast monsoon season when the city receives nearly 62% of its annual rainfall and Tamil Nadu about 48% of its yearly total. Nov, the city’s wettest month, alone receives an average 37cm of rainfall.In the first specialised El Nino bulletin released by Indian National Centre for Ocean Information Services (INCOIS), the agency said the event is expected to strengthen through the year, with sea surface temperatures over the Indian Ocean remaining above normal till April-May 2027. It has begun issuing monthly bulletins to monitor the impact of El Nino on the southwest and northeast monsoons and India’s maritime sector.“The bulletin confirms that the El Nino event continues to develop and is expected to peak in the winter season (Nov 2026 to Jan 2027),” a release from INCOIS said.The bulletin warned that warmer seas could trigger increased coral bleaching, more episodes of marine heatwaves and a reduction in fish catch. Fish stocks, particularly sardines and mackerel, may migrate to cooler waters or experience poor recruitment and slower growth, affecting catches. It also warned of increased coastal erosion and flooding along India’s east coast during the southwest monsoon as the Bay of Bengal remains rough, while the northern Indian Ocean is expected to remain under thermal stress.“The sea state in the Arabian Sea and the west coast is likely to be calmer than usual, which can increase the window for operations of various marine sectors. Coastal erosion and inundation are likely to be less on the west coast during the ongoing monsoon season,” INCOIS researchers said.The timing of the El Nino peak has drawn attention because it overlaps with Tamil Nadu’s principal rainy season. Long-term IMD research analysing data from 1875 to 1997 found that northeast monsoon rainfall over southeast peninsular India is generally higher than normal during El Nino years and 17 of 22 El Nino years during the study period recorded above-normal northeast monsoon rainfall over Tamil Nadu.Meteorologists, however, caution that El Nino is only one of several climate drivers. The eventual performance of the northeast monsoon also depends on factors such as the Indian Ocean Dipole, Madden-Julian Oscillation, Bay of Bengal sea-surface temperatures and the frequency and track of low-pressure systems and cyclones. Research on the 2015 Chennai floods also showed that while the extreme El Nino enhanced the event, unusually warm Bay of Bengal waters played an equally important role in producing the unprecedented rainfall.The previous El Nino peaked during the 2023 northeast monsoon, when Tamil Nadu witnessed multiple extreme rainfall episodes, including the Dec floods in the city and the record-breaking deluge over the southern districts.
