IMD warns of harsh winter as La Nina set to emerge; monsoon withdrawal delayed

New Delhi: India could be in for a harsh winter as La Nina conditions are expected to emerge by October-November, potentially bringing severe cold waves to northwest and central India, according to the India Meteorological Department (IMD).

Meanwhile, the southwest monsoon season, which ended on Monday with an 8% surplus in rainfall for the June-September period, is experiencing a delayed withdrawal that is now expected to be completed by 17 October, IMD chief Mrutyunjay Mohapatra said.

“Rainfall activity is increasing in the week commencing from 17 October. If that goes right, we can expect that northeastern monsoon will set in over the southeastern peninsula by 17 October,” Mohapatra said during a briefing on the monsoon’s performance and the October weather outlook. 

He clarified that despite this year’s delayed monsoon withdrawal, the official withdrawal date for the entire country remains unchanged. “We are expecting that there will be withdrawal in the next one-week from northeastern India and then central India gradually. From the entire country, we will keep monitoring and be updating you on a weekly and daily basis.”

Typically, the monsoon begins its withdrawal on 17 September and exits the country by 15 October. This year, the withdrawal process was delayed due to a low-pressure system in northwest India. The withdrawal, which started on 23 September, has stalled in Punjab and surrounding areas.

This year, India experienced six depressions, 14 low-pressure systems in the Bay of Bengal, and one cyclonic storm, ‘ASNA,’ in the Arabian Sea. Notably, there have only been three cyclonic storms in August over the Arabian Sea between 1891 and 2023, Mohapatra highlighted.

Despite a sluggish start, the country received 7.6% above-normal rainfall during the 2024 southwest monsoon, with a total of 934.8 mm, which is 107.6% of the long-period average (LPA). Regions including Rajasthan, Gujarat, West Madhya Pradesh, Maharashtra, Telangana, and Andhra Pradesh saw excess rainfall, according to IMD data.

The southwest monsoon arrived on the Kerala coast on 30 May, a day earlier than usual. The season accounts for 75% of India’s annual rainfall, critical for irrigation, reservoirs, and the broader economy. June and July are particularly important for the planting of kharif crops such as rice, pulses, oilseeds, and cotton.

As of 30 September, 21 meteorological subdivisions reported normal rainfall, while 10 recorded excess and three saw deficient showers. The IMD also reported heavy human tolls from extreme weather events during the season, with Kerala losing 397 lives due to floods and heavy rain, Assam 102, and Madhya Pradesh 100. Conversely, Jharkhand and Rajasthan saw casualties from heatwaves, with 13 and 4 deaths, respectively.

Turning to La Nina’s delayed formation, Mohapatra acknowledged that global predictions on its emergence have been inaccurate. However, there is now a 71% chance that La Nina will develop by October-November, which could result in colder-than-normal temperatures in northern India. 

Historically, La Nina has brought below-normal temperatures to northwest India, he said. “La Nina condition is still weak and how much it will strengthen in January or February, that we have to monitor.”

He added that cold wave conditions are likely in northwest and central India this winter, but the severity will be detailed in the monthly forecast issued in November.

Looking ahead, October is forecasted to bring above-normal rainfall, exceeding 115% of the LPA. The historical LPA for October rainfall, based on data from 1971 to 2020, is 75.4 mm. However, certain areas in northeast and northwest India, as well as pockets of the southern peninsula, may see normal to below-normal rainfall.

Also read | Mint Explainer: Return of La Nina and its impact on Indian monsoon, agriculture

October also marks the onset of the three-month-long northeast monsoon (October-December), which primarily delivers vital rainfall and cooler temperatures to southeastern India. While this rain helps replenish water resources, it also increases the risk of cyclonic depressions and heavy precipitation.

Temperature-wise, most parts of the country are expected to see above-normal minimum temperatures in October. Maximum temperatures are likely to be above-normal as well, except in central India and parts of the southern peninsula, where normal to below-normal temperatures are anticipated, IMD said.