| Scramble from rain outside the Mohammad Ali Park puja. Picture by Pradip Sanyal
Calcutta, Oct. 18: Rain clouds loom over Ashtami, but the Met office predicts better weather than today.
“We expect rains at isolated places tomorrow. The weather, however, is expected to be better. If you have noticed, the sky has cleared considerably from this evening,” a Met official said.
Many Calcutta streets, especially in the north, were under a foot of water after the downpour today. Lake Town, S.K. Deb Road, Dum Dum Park and Bangur Avenue were among the neighbourhoods worst affected.
A trough of low pressure that formed over Gangetic Bengal over the past three days, extending from east Bihar to south-west Bay of Bengal, has been bringing in moisture from the sea.
“Huge columns of cumulonimbus clouds — 4km to 6km tall — could be seen on the radar this morning over Calcutta and its neighbouring areas, including North and South 24-Parganas and Nadia,” a Met official said. “The depth of the clouds was more in the north of the city, so the intensity of rain was more there.”
The Alipore Met office, located in south Calcutta, recorded 18.4mm of rain between 8.30pm on Wednesday and 2.30pm on Thursday. In Dum Dum, in the north, the rainfall was 51mm.
Officials said the monsoon, which is expected to withdraw in a few days, was temporarily activated because of the trough of low pressure. “Normally, the monsoon bids adieu by October 10,” the official said.
Met officials explained that a trough of low pressure hovers over the eastern region during monsoon. It keeps shifting depending on the wind flow pattern, among other things, in the upper atmosphere.
“If the wind pattern is favourable and drives the trough of low pressure away from Bengal, we can get a clear sky,” an official said. “But it will be difficult for the monsoon to withdraw soon if the trough of low pressure persists.”
The low pressure trough had veered towards Bangladesh on Tuesday, a Met official said. “We had predicted rain in isolated areas. But we did not realise there would be such thundercloud build-up in the north,” the official said.