A woman shields herself from rain at Esplanade on Friday. (Bishwarup Dutta)
A low-pressure area that brought rain to the city on Sunday is likely to cause more showers over the next two days.
The city received 18.8mm of rain in 24 hours till 5.30pm on Sunday, triggered by a low-pressure area over the Bay that gained strength near the Bengal coast and boosted the flow of moisture towards land.
“A cyclonic circulation over north Bay of Bengal and adjoining areas has gained strength to become a low-pressure area. It is attracting a lot of moisture. So rainfall will continue in south Bengal and Odisha,” said Gokul Chandra Debnath, director, India Meteorological Department, Calcutta.
“The system will intensify further in the next 24 hours to become a well-marked low pressure area.”
The forecast for both Monday and Tuesday is “moderate rainfall”, which is up to 35.5mm of rain a day.
The showers may subside from Wednesday as the weather system is likely to move towards Odisha by then, tracing a north-western trajectory that is typical of any low-pressure zone over the Bay at this time of the year.
“We have been getting one weather system after another over north Bay of Bengal recently but most are forming near the Odisha coast and then moving further north-west, bringing limited rain to Calcutta. But the present system has formed close to the Bengal coast. So the city can expect more rainfall than it has been getting lately,” said a weather expert.
Rainfall intensifies if there is a depression over the sea nearby. South Bengal usually gets two such systems in July but this year there was only one, and that, too, on land.
A low-pressure belt sustains itself while on sea and draws air towards itself because of an atmospheric pressure that is lower than that of the surroundings. Such a formation is much less effective after making landfall.
Sunday’s cloudcover and showers brought the temperature down, with the maximum dropping almost four notches from Tuesday’s 35.6 degrees to 31.9, which is normal for this time of the year.
Met experts said the maximum was likely to hover around 32 degrees on Monday and Tuesday.
The monsoon arrived in Calcutta 10 days behind schedule. The city usually gets 283.5mm of rain in June but this year it received 217mm, a deficit of 23.1 per cent.
The rainfall picked up at the start of July, with the city being lashed by over 180mm of rain on the first two days of the month. The rest of the month didn’t see heavy rainfall even for a day but the monthly aggregate touched 376mm, a surplus of four per cent.
August usually brings 352.4mm of rain to Calcutta.