Pune: Major El Nino events often weaken substantially before the subsequent monsoon, meteorologists told TOI on Saturday, easing concerns about the system's potential impact on India's 2027 rainy season. This comes amid forecasts that a strong El Nino could develop by late 2026 or winter and persist into early 2027.
Historical Patterns of Strong El Nino Events
An analysis of some of the strongest El Nino events since 1951, including the prominent episodes of 1982-83, 1997-98 and 2015-16, reveals a consistent pattern. These events tend to strengthen gradually during the latter half of the first year, reach peak intensity around the year-end or during winter, and then weaken before India's June-September monsoon season arrives.
For instance, during the record-setting 1997-98 El Nino, sea surface temperature anomalies in the central and eastern Pacific rose steadily from 1.6 degrees Celsius during June-July-August to 1.9 degrees Celsius in July-August-September. The warming intensified further to 2.3 degrees Celsius in September-October-November and peaked at around 2.4 degrees Celsius in October-November-December. By mid-1998, however, the system had weakened significantly and transitioned into La Nina conditions.
A similar trajectory was seen during the 2015-16 El Nino event. Ocean temperatures increased from 1.6 degrees Celsius in June-July-August to 1.9 degrees Celsius in July-August-September, eventually crossing the 2-degree Celsius mark later in the year and peaking during winter. By the time the following monsoon season arrived in 2016, the event had already weakened.
IMD Official's Perspective
According to an official from the India Meteorological Department (IMD), this pattern is characteristic of strong El Nino events. "Strong El Nino reaches peak strength towards the end of the year or early the next year and then weakens. Before the following monsoon, it often becomes neutral or shifts towards La Nina, which is what we expect in 2027," the official said.
The official said historical patterns suggested strong El Nino episodes often weakened and transitioned towards neutral or La Nina conditions. He said subsurface cooling signals over the western Pacific were already emerging and might point towards such a shift next year. He, however, cautioned that projections extending too far ahead should be interpreted carefully, as forecast skill tends to decline at longer lead times.
Expert Views on El Nino and Monsoon Impact
GP Sharma, president of meteorology and climate change at Skymet, emphasised that stronger El Nino events did not necessarily produce stronger monsoon impacts over India. "The degree of El Nino does not matter much. Weaker El Nino events have coincided with drought years, while stronger ones have not always produced severe impacts," he said.
Sharma said among six very strong El Nino events recorded since 1950, the outcomes varied widely, including one severe drought, two moderate droughts, two normal monsoon seasons and one below-normal year. This variability highlighted that other climatic factors also played an important role in determining India's monsoon performance, he added.
Former Indian Institute of Tropical Meteorology (IITM) director R Krishnan echoed this view, citing the 1997 event as a key example. "In 1997, concerns had emerged because a very strong El Nino was developing, but India eventually saw a normal monsoon. By July the following year, it had already transitioned towards La Nina," he said.
Conclusion and Outlook
Overall, while a strong El Nino may persist into early 2027, experts said historical patterns did not support the assumption that peak conditions would continue into the monsoon season. Instead, the likelihood of weakening, or even a transition to La Nina, suggested that the eventual impact on India's 2027 monsoon remained uncertain and could not be judged solely on the expected strength of the El Nino event.
El Nino is a periodic warming of sea-surface temperatures across the central and eastern Pacific Ocean that can disrupt global weather patterns. For India, it often spells weaker monsoon currents, patchy rain, crop stress, and reservoir strain. Its opposite phase, La Nina, cools Pacific waters and generally boosts monsoon circulation, often bringing stronger seasonal downpours across the subcontinent.
