The low-pressure system on the Bay of Bengal intensified into a depression on Wednesday, the Met office said.
The system is poised to become stronger and turn into a deep depression by Thursday morning before heading towards the Andhra Pradesh coast, from where it is expected to recurve towards the Odisha-Bengal coastline.
Under the influence of the system, the sky over Calcutta is likely to be cloudy in parts from Thursday. Showers are likely in the afternoon and evening, when Australia and South Africa will lock horns at the Eden Gardens for a slot in the World Cup final.
The intensity of the showers is likely to go up on Friday and Saturday.
“The depression over westcentral Bay of Bengal moved northwestwards with a speed of 13kmph during the past three hours and lay centred at 11.30am on November 15 over the same region, about 470km southeast of Visakhapatnam (Andhra Pradesh), 620km south-southeast of Paradip (Odisha) and 770km south of Digha (West Bengal),” said a Met bulletin issued on Wednesday afternoon.
“It is likely to move initially northwestwards, then north-northwestwards and intensify into a deep depression over westcentral Bay of Bengal off Andhra Pradesh coast on the morning of November 16. Thereafter, it would recurve north-northeastwards and reach northwest Bay of Bengal off the Odisha coast on the morning of November 17; and off North Odisha-West Bengal coasts on November 18 morning.”
The weather in Calcutta was reasonably bright and sunny on Wednesday. But an overcast spell is on its way, said a Met official.
“It will be cloudy in parts on Thursday. Some rain is expected in the second half. The volume and spread of the showers is likely to go up on Friday and Saturday as the system comes near the Bengal coast,” said G.K. Das, director, India Meteorological Department, Calcutta.
The official Met forecast said heavy rain in expected in South-24 Parganas, North-24 Parganas and East Midnapore.
The forecast did not say anything on the future of the system after November 18.
A Met official in Calcutta said the system is unlikely to intensify into a cyclone because of a “strong vertical wind shear”.
“If it follows the projected path, it is likely to head towards the Bangladesh coast from the east of the Sunderbans,” he said.