The morning was bright and sunny on Sunday but as the day progressed, clouds pushed the sun back.
Diwali was also likely to be cloudy in the coastal areas of south Bengal, including Calcutta. “Rain is not completely ruled out but the chances are very slim in Calcutta. South 24-Parganas and East Midnapore are more likely to get very light rain,” said a Met official in Alipore.
The weather in Calcutta had remained bright and sunny for days after the retreat of southwest monsoon on October 13. The minimum humidity level had dropped to around 40% from over 70% in the first week of October, when the city got drenched almost every day.
Fresh moisture incursion is taking place now. “The moisture is being injected by the north-easterly winds. There is an indirect effect of a system on the Bay. Some of the winds from the Northeast are coming via the Bay ” said H.R. Biswas, head of the weather section at the Regional Meteorological Office in Alipore.
“The upper air cyclonic circulation over south Andaman Sea and adjoining southeast Bay of Bengal extending upto 1.5km above mean sea level persists,” said a Met report.
“Under its influence, a low pressure area is likely to form over southeast Bay of Bengal around October 21. It is likely to move west-northwestwards and intensify into a depression over central parts of south Bay of Bengal and adjoining west-central Bay of Bengal during subsequent 48 hours,” the report said.
October and November provide conducive conditions for a Bay system to intensify into a cyclone. What will happen to this system after it turns into a depression is not clear yet. “The projected path will emerge after the low-pressure area takes shape,” said a Met official.