La Nina likely to miss Southwest Monsoon

INCOIS scientists predict delayed La Nina, impacting Indian monsoon with potential for lower rainfall later in the year.

The early signs of the likelihood of a La Nina weather pattern in the eastern Pacific Ocean are clear, but it looks like it is going to miss the peak Indian Southwest Monsoon, which will end next month, according to scientists at Indian National Centre for Ocean Information Services (INCOIS).

The agency, which works under the Ministry of Earth Sciences (MoES), has indicated in its latest bulletin that the La Nina could only emerge towards November, not in September as forecast earlier. As such, only a small amount of rainfall is likely later in the year.

“The El Nino neutral conditions are clearly visible in the western Pacific for sometime, and this is expected to continue. But, the chances of La Nina emerging in the last quarter of the year is only about 55%... There are mild cooling conditions in the Eastern Pacific, but we cannot call it La Nina as of now,” explained head of Ocean Modelling and Data Assimilation (OMDA) division P.A. Francis.

El Niño is warming of the eastern Pacific Ocean and has been observed as having 80% chances of causing an adverse effect on the Indian summer monsoon and the economic well-being of the country. It has also been found causing prolonged strong marine heatwaves in the northern Indian Ocean, damaging the ecological balance, coral reefs and causing significant losses to the fishing industry. On the other hand, La Nina has been observed as having 75% chances of bringing more rains during the monsoon.

The scientist pointed out that a large part of the country receives 90% of its annual rainfall from the Southwest Monsoon. The Northeast Monsoon, which prevails between October and December, usually brings relatively lesser rainfall, except in southeastern parts of the country.

Mr. Francis said La Nina could have strengthened the monsoon had it evolved during the July-August-September period. Nonetheless, it cannot be concluded that La Nina would bring heavy rains again later this year because several studies had noted lower rainfall during Northeast Monsoon under the influence of La Nina.

INCOIS had earlier forecast La Nina to peak in November with a 70% probability and has downgraded it to 45-60% and likely to continue till January. Thereafter, the chances of El Nino neutral conditions are high from February to April 2025.