Forty-five per cent rain deficit at the end of August. Eighteen per cent deficit into the fourth week of September.
A rainy September has drastically reduced the monsoon deficit for Calcutta.
“June, July and August had all recorded rain deficits. At the start of August, the cumulative rain deficit for Calcutta was around 45 per cent. Now, it is 18 per cent. The gap has been reduced because of consistent rain in September,” said G.K. Das, director, India Meteorological Department, Calcutta.
Sunday is also likely to be rainy in Calcutta but the weather is likely to improve from Monday, according to the Met forecast.
From September 1 to 22, the Met office has recorded around 350mm of rain in Alipore, which serves as the official log book for Calcutta. The average rainfall due in the same period is around 213mm. The surplus is 64 per cent.
The past few days have seen persistent rainfall and overcast conditions. The rain came in multiple spells, some of them sharp.
A cyclonic circulation that had taken shape over the Bay of Bengal earlier this week and the monsoon trough are behind the current wet spell, said Das.
“From the Bay of Bengal, it entered Odisha. From Odisha, it moved to Jharkhand. Now, it is over southwest Bihar and adjoining areas. The monsoon trough extends to Manipur via Krishnagar (in Nadia). Another trough extends from Bihar to Assam. These are the main factors that are causing rain.”
While Bihar and north Bengal are getting heavy rain, south Bengal is also getting rain, he said.
New system
“ A cyclonic circulation is likely to form over north Andaman sea and neighbourhood on September 29,” said a Met update on Saturday.
“Under its influence, a low-pressure area is likely to form over the north Andaman sea and adjoining east-central Bay of Bengal during the subsequent 24 hours,” it added.
“It is still too early to say anything. The system will turn into a low-pressure. What happens beyond that is still uncertain,” said Das.