Mumbai monsoon misses withdrawal date; could take another 8-10 days, says IMD

Published on Oct 08, 2020 11:53 PM IST
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HT Image
By, Mumbai

The southwest monsoon has extended beyond the normal withdrawal date for the city — October 8 — with another eight to 10 days for the season to end, the weather bureau said.

In April this year, the India Meteorological Department (IMD) had announced the new onset date for Mumbai as June 11 as opposed to June 10 originally, and the new withdrawal date as October 8 against September 29. This meant that the normal duration of the entire season over Mumbai would span 120 days as opposed to 112 days.

This year monsoon onset was declared on June 14 and the season has already spanned 116 days. It was the second wettest monsoon in history in the city.

“Mumbai has missed its normal withdrawal date, but it cannot be said that it is a delayed withdrawal yet because the withdrawal date (October 8) has a standard deviation of plus-minus seven days. So it will not be a delayed withdrawal if declared till October 15,” said Mrutyunjay Mohapatra, director general, IMD. IMD had earlier this month said that withdrawal was expected between October 9 and 15.

KS Hosalikar, deputy director general, western region, IMD, said, “With the prevailing situation, it may take another eight to 10 days for monsoon withdrawal to be declared from Maharashtra and Mumbai.”

The weather bureau said rainfall activity is expected to enhance over Maharashtra from October 10 onwards with a yellow alert for isolated areas in Marathwada, Vidarbha and parts of central Maharashtra and south Konkan. However, it is not likely to lead to heavy rain for north Konkan including Mumbai. “We are expecting the formation of a low pressure area in the Bay of Bengal which will increase rainfall over Maharashtra, thus delaying withdrawal,” said Mohapatra.

Last year, monsoon withdrawal from Mumbai was declared on October 14 while it was October 6 in 2018, and as late as October 24 in 2017. The trend was observed in previous years as the southwest monsoon withdrew from the city on October 14 in 2016, October 15 in 2015, October 20 in 2014. Prior to that, the range had been between October 14 and 18.

Independent meteorologists said withdrawal for Mumbai and Maharashtra was not likely before October 20. “The low pressure systems from the Bay of Bengal will keep the monsoon circulation active for some more days. La Niña (when the western Pacific Ocean warms up creating a low pressure near Australia pulling winds from the Indian Ocean, strengthening equatorial dynamics keeping southwest monsoon circulation active) is allowing the equatorial dynamics to be vigorous, which is, in turn, showing up in the form of low pressure systems in the Bay of Bengal. The intertropical convergence zone (ITCZ) is not moving down, hence keeping the monsoon circulation active. This translates into delayed withdrawal,” said professor Sridhar Balasubramanian, department of mechanical engineering and IDP Climate Studies, Indian Institute of Technology-Bombay.

Akshay Deoras, independent meteorologist and PhD researcher at the University of Reading, United Kingdom, said, “Consecutive low-pressure systems from the Bay of Bengal will prevent the official announcement of the monsoon’s withdrawal, which is largely dependent on the requirement of dry weather conditions. However, from October 15, main features of the southwest monsoon circulation (such as wind direction) will no longer prevail; so whatever rainfall will occur, will be purely due to the non-southwest monsoon weather pattern.”

Meanwhile, the city and suburbs recorded no rain on Thursday with day and night temperatures a degree above normal.


    Badri Chatterjee is an environment correspondent at Hindustan Times, Mumbai. He writes about environment issues - air, water and noise pollution, climate change - weather, wildlife - forests, marine and mangrove conservation

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