Mumbai and Kolkata both are few knocks away from the seasonal monsoon 2020. Both the cities have experienced hefty pre-monsoon showers in the first week of June. There is a close race between the two to grab the monsoon first and winner is going to emerge shortly, with a possible ‘tie’ as an outside chance.
Southwest Monsoon has been limited to parts of South Peninsula below 15deg N along the west coast and about 13deg N on the east coast. It is Marginally behind schedule over Peninsular India and yet to make appearance over Northeast and East India so far. Few days of discrepancy can always be compensated without even a dent on performance.
Normal date for onset of monsoon for Mumbai and Kolkata is 11th June and 12th June respectively, means it is simultaneous arrival. But more often Mumbai scores over Kolkata and comes first on nearly 8 out of 10 occasions. While Bay of Bengal is responsible for ushering monsoon over Kolkata, Mumbai banks hope on either of two: Bay of Bengal or Arabian Sea. Any monsoon system over the Bay of Bengal builds up a surge along the west coast enhancing rainfall to push monsoon current over Mumbai. On the other hand, off shore trough or any vortex along the west coast also become instrumental for onset over Mumbai.
During monsoon season Mumbai rains much heavier than Kolkata. Average seasonal rainfall for Mumbai and Kolkata is 2260 mm and1360 mm respectively for four month long season from June to September. Commencement and cessation of monsoon activity for both the cities is nearly the same. However duration of intense rainy spells is much longer in case of Mumbai wherein 8-10 days of 100mm or more are common during the season.
Presently a low pressure area in the Bay of Bengal is likely to become well marked in the next 24 hours. This weather system will move northwest to cross Odisha coast in the subsequent 24 hours. Intensity and spread of rainfall is going to increase thereafter over Gangetic West Bengal and the capital city of Kolkata can expect monsoon showers anytime around 12 – 13 June. The monsoon surge is going to build up along the west coast also and the off shore trough all along the coast will become active. Second round of pre-monsoon showers are going to lash the financial capital between 11-13 June and paving way for monsoon arrival on the 14th June. City may have to wait a little further to record first three digit rainfall in 24 hours of season 2020.