Southwest monsoon to make landfall in Kerala on May 27

Representational image

Southwest monsoon is all set to touch base along the south west coast of Kerala on May 27, four days before the traditional onset date of June 1. This was announced by the Indian Meteorological Department on Friday.

Kerala has already been pummelled by excess summer showers and the 'Asani' effect continues to pound various parts of Kerala with heavy rains. Fear is, the southwest monsoon coming on top of heavy pre-monsoon rains, like in 2018 and 2019, could once again set off floods. However, the IMD has predicted a normal southwest monsoon this year. There will also be an equal distribution of rainfall across the country, the IMD had said.

The IMD on Friday said that as the monsoon progresses northward, relief from scorching summer temperatures is experienced over the areas. Southwest monsoon normally sets in over Kerala on June 1 with a standard deviation of about 7 days. This time it would be May 27. Skymet, a leading private weather forecast company, has predicted it would be May 26.

The IMD has been issuing operational forecasts for the date of monsoon onset over Kerala from 2005 onwards. Its 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.

In fact in the last five years, the monsoon swooped down on the Kerala coast on the very day predicted; May 30 and May 29 in 2017 and 2018. In the other three years, the difference between forecast and the original onset was not more than four days.

An indigenously developed state of the art statistical model with a model error of plus or minus four days is used for the purpose. The six 'predictors' used in the models are: one, Minimum Temperatures over North-west India; two, Pre-monsoon rainfall peak over south Peninsula; three, Outgoing Long wave Radiation (OLR) over south China Sea; four, Lower tropospheric zonal wind over southeast Indian Ocean; five, upper tropospheric zonal wind over the east equatorial Indian Ocean; six, Outgoing Long wave Radiation (OLR) over the south-west Pacific region.

Though southwest monsoon officially begins in the Indian mainland when it makes landfall in Kerala, initial monsoon rains are experienced over south Andaman Sea and the monsoon winds then advance north-westwards across the Bay of Bengal. Traditionally, the southwest monsoon advances over the Andaman Sea around May 22. According to the IMD, this too could be advanced.

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

Nonetheless, 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.

Scorching summers in the North
Meanwhile, most parts of north India experienced scorching summers with maximum temperatures touching 48 degrees Celsius in Barmer in Rajasthan on Thursday.

At least 29 cities across Rajasthan, Haryana, Gujarat, Madhya Pradesh and Maharashtra reported temperatures in excess of 44 degrees Celsius.

Barmer was the hottest with a maximum temperature of 48.1 degrees, followed by Ganganagar (47.3), Bikaner and Jaisalmer (47.2), Churu (46.9), Kota (46.7), Khargone (46.4), Rajgarh and Jodhpur (46).

The weather office has said that no significant change in maximum temperatures was very likely over Northwest India during the next three days and the mercury could fall by 2-3 degrees Celsius thereafter.

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