The IMD has forecast the onset of the Southwest Monsoon over Kerala on May 26, with a model error of +- 4 days. While the monsoon brings relief, severe heatwave conditions are expected to continue over Northwest and Central India for several days.
The Southwest Monsoon is likely to set in over Kerala on May 26, with a model error margin of +- 4 days, said the India Meteorological Department (IMD) on Friday.

Conditions are favourable for the further advancement of the Southwest Monsoon into parts of the South Bay of Bengal, the Andaman Sea, and the Andaman and Nicobar Islands during the next 24 hours.
Heatwave Amidst Monsoon Arrival
Heatwave to severe heatwave conditions are likely to prevail over Northwest and Central India for several days during the week.
Significance of Monsoon Onset
The advance of the southwest monsoon over the Indian mainland is marked by its onset over Kerala and is considered an important indicator marking the transition from the hot and dry season to the rainy season. As the monsoon progresses northward, it brings relief from scorching summer temperatures across several regions.
According to the IMD, the southwest monsoon normally sets in over Kerala around June 1, with a standard deviation of about seven days.
IMD's Forecasting Model and Accuracy
The IMD has been issuing operational forecasts for the date of monsoon onset over Kerala since 2005. The forecast is based on an indigenously developed statistical model with a model error of +- 4 days.
The model uses six predictors, including minimum temperatures over northwest India, pre-monsoon rainfall peak over the south peninsula, outgoing longwave radiation over the South China Sea and southwest Pacific region, and lower tropospheric zonal winds over the southeast Indian Ocean and northeast Indian Ocean.
IMD's forecasts over the past 21 years (2005-2025) have been largely accurate except in 2015. In the most recent six-year period (2020-2025), the forecast performance remained close to actual onset dates, with minor variations between predicted and observed arrivals of the monsoon. (ANI)
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