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Monsoon onset early over Kerala this year, expected to be ‘normal’

The Met department had already announced a month ago that the monsoon rainfall this year over the country as a whole is most likely to be normal – quantitatively 99 per cent of the Long Period Average (LPA).

IANS | New Delhi |

Bringing cheer to a large part of the Indian sub-continent, the Southwest Monsoon is likely to hit the Kerala coast on May 27, much ahead of its scheduled arrival date of June 1, the India Meteorological Department (IMD) announced on Friday.

Monsoon arrival is eagerly awaited as it has a deep impact on India’s agriculture and economy and hence, is termed as the real Finance Minister of India.

The Met department had already announced a month ago that the monsoon rainfall this year over the country as a whole is most likely to be normal – quantitatively 99 per cent of the Long Period Average (LPA).

The next update would be announced sometime in May last week when the IMD would come up with an updated, if any, date of onset over Kerala and also the quantitative forecast.

“The monsoon onset over Kerala is likely to be on May 27 with a model error of plus or minus four days,” the IMD said in a statement.

The initial monsoon rains are experienced over south Andaman Sea and the monsoon winds then advance north-westwards across the Bay of Bengal towards the Indian landmass. As per the normal dates of monsoon onset/progress, the Southwest Monsoon advances over the Andaman Sea around May 22 in most years.

“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 May 15,” it said.

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 IMD reminded.

Except in 2015, the IMD’s operational forecasts of the date of monsoon onset over Kerala – with a standard deviation of seven days – during the past 17 years (from 2005 till 2021) were proved correct. IF we look at last five years, in 2017, the monsoon onset happened on May 30, same as forecast onset date; in 2018 too, it was May 29 for both; in 2019, the forecast date was June 6 and actual onset happened on June 8; in 2020, the forecast date was June 5 but onset happened on June 1 while in 2021, the onset happened on June 3 against the forecast date of May 31.

Advance of the southwest monsoon over the Indian mainland is marked by monsoon onset over Kerala and is an important indicator characterising the transition from hot and dry season to a rainy season.

The IMD has been issuing operational forecasts for the date of monsoon onset over Kerala from 2005 onwards using an indigenously developed state of the art statistical model with a model error of plus minus 4 days.