A cyclonic circulation took shape on the Bay of Bengal on Thursday, the first since the arrival of the monsoon in south Bengal.
For Kolkata, the system promises rainy days ahead. But heavy rain is unlikely because the circulation is reasonably far from the city, said Met officials.
The circulation has taken shape over the west-central and the adjoining northwest Bay, said a Met report.
“The cyclonic circulation over west-central and adjoining northwest Bay persists... between 3.1 and 5.8 km above mean sea level,” the report said.
“The system is off north Andhra Pradesh and south Odisha coasts. It is not close to the Bengal coast. But the monsoon currents over the Bay have been strengthened because of the system and the coastal areas of South Bengal, including Kolkata, will also get rain at least till Sunday,” said a Met official.
“The rain is unlikely to be heavy in Kolkata. But it is expected to be uniform, unlike the scattered showers now,” he said.
In Met parlance, 60mm of rain in 24 hours qualifies as heavy.
The showers are likely to be accompanied by frequent streaks of lightning, the Met office has warned.
The northwest Bay is off the Odisha coast while the west-central Bay is closer to Andhra Pradesh.
Kolkata is usually most affected by a system over the northeast Bay, which is also closer to the Bangladesh coastline.
Kolkata was overcast for most of Thursday. Some parts of the city got a spell of rain in the forenoon. But there were areas that were dry.
The Met office recorded just under 5mm of rain in Alipore, which serves as the official figure for Kolkata.
A trough of low pressure that extended from Punjab to Assam via north Bengal dissipated on Thursday, said a Met official.
Now that the trough is gone, the intensity of rainfall is likely to decrease in north Bengal over the next 48 hours, said the official.
Several areas in Jalpaiguri, Alipurduar and Kalimpong continued to receive heavy rain on Thursday.