Monsoon onset over Kerala likely to take place on May 27, earlier than the normal date

New Delhi, May 13, 2022

The India Meteorological Department (IMD) today said the onset of the southwest monsoon over Kerala this year is likely to be on May 27, earlier than the normal date, marking its advance over Indian mainland.

"This year, the onset of southwest monsoon over Kerala is likely to be earlier than normal date of onset. The monsoon onset over Kerala is likely to be on 27th May with a model error of +/- 4 days," a press release from IMD said.

The advance of the monsoon over Indian mainland is an important indicactor characterizing the transition from the hot and dry summer to a rainy season. As the monsoon progresses northward, relief from scorching summer temperatures is experienced over the areas, the release pointed out.

The southwest monsoon normally sets in over Kerala on June 1 with a standard deviation of about seven days.

The IMD has been issuing operational forecasts for the date of monsoon onset over Kerala from 2005 onwards. An indigenously developed state of the art statistical model with a model error of +/- 4 days is used for the purpose.

The six Predictors used in the models are; i) Minimum Temperatures over North-west India, ii) Pre-monsoon rainfall peak over south Peninsula, iii) Outgoing Long wave Radiation (OLR) over south China Sea, (iv) Lower tropospheric zonal wind over southeast Indian Ocean, (v) Upper tropospheric zonal wind over the east equatorial Indian Ocean, and (vi) Outgoing Long wave Radiation (OLR) over the south-west Pacific region.

"IMD’s operational forecasts of the date of monsoon onset over Kerala during the past 17 years (2005-2021) were proved to be correct except in 2015," the release said.

In the Indian monsoon region, initial monsoon rains are experienced over south Andaman Sea and the monsoon winds then advance north-westwards across the Bay of Bengal.

As per the normal dates of monsoon onset and progress, the southwest monsoon advances over the Andaman Sea around May 22.

"In association with enhanced cross equatorial winds, conditions are becoming favorable for advance of Southwest Monsoon into South Andaman Sea, Nicobar Islands and some parts of southeast Bay of Bengal, around 15th May, 2022.

"Past data suggest that there is no association of the date of monsoon advance over the Andaman Sea either with the date of monsoon onset over Kerala or with the seasonal monsoon rainfall over the country," the release added.

NNN