Chennai is being ravaged repeatedly with heavy rains, since the time of onset of northeast monsoon on 25thOctober 2021. The capital city has been bashed thrice in this month between 06-08 Nov, 10-12 Nov and 18-19 Nov. The city has clocked 808mm of rainfall between 01st- 22nd Nov, against its monthly normal of 374.4mm.
Chennai has not received such copious rains, more than double the normal in November, in the recent past, except in 2015. Factually, 2018 & 2019 remained mild observing deficit rains and 2020 barely managing to cross the average rainfall. Deluge of 2015 still stands tall with a mammoth figure of 1049.3mm , marginally behind the all time record 0f 1088.4mm, more than a century ago in 1918.
Chennai is expected to have another round of heavy rains between 25th and 27th November 2021. These rains will drench some more parts of North Coastal Tamil Nadu including Puducherry and Karaikal. The rainfall belt will also extend to cover parts of South Coastal Andhra Pradesh, like the last time between 17th and 19thNovember.
Coastal towns starting with Ongole and Nellore and going right up to Machilipatnam will be at risk of heavy to very heavy rains, between 27th and 29thNovember. Chennai stands a chance to compete and possibly beat the rainfall record of 2015.
Presently, a broad cyclonic circulation is marked over southern parts of East and Central Bay of Bengal. This will become more marked and also shift westward towards Sri Lanka and Southwest Bay of Bengal in the next 48hr. Thereafter, it will be moving slowly, meandering over Gulf of Mannar, Comorin Sea and Southwest Bay of Bengal, with an extended trough along coastal Tamil Nadu and Andhra Pradesh.
Also, there is another weather system waiting in the wings over West Pacific likely to enter Gulf of Thailand and later move to Andaman Sea during fag end of the month.