The onset of winter has been delayed again following the appearance of yet another weather formation over the Bay that is blocking the North Wind. The Met office has ruled out the possibility of a drop in the mercury for at least the next 24 hours.
“A low-pressure system that developed over the south Bay of Bengal on Monday, and has been more or less static since, has become a well-marked low-pressure area. It is gaining in strength by the hour and likely to become a depression by Thursday. Only after it happens will it become clear in which direction it will go and the kind of effect it will have on the Calcutta weather,” said Gokul Chandra Debnath, director, India Meteorological Department, Calcutta.
The excess moisture blowing into the city air because of the low-pressure area is pushing up the mercury, with the minimum temperature rising from 16 degrees Celsius on Monday to 17.9 degrees on Wednesday (two notches above normal). The ascent has made the first four days of December the third warmest in the past 10 years (see chart).
Met officials said the warm spell could be over by the weekend if the weather system moves towards the Tamil Nadu coast. But if it makes landfall on the Andhra Pradesh coast, there will be enough moisture flow into the city for the warm phase to stretch to the next week.
“The trajectory and speed of the weather formation can be determined after it becomes a depression. So only on Thursday, when it is expected to become one, will we be able to say where and when it will hit land,” said a weather scientist.
There is, however, no chance of rainfall in the city because of the system, he clarified.
Calcutta had a good start to the pre-winter season with the minimum temperature in the city touching 17.3 as early as November 14, then three degrees below normal, because of early snowfall in Jammu and Kashmir and clear skies in Calcutta.
But after that came two cyclonic storms, Helen and Lehar, in quick succession and a trough of low pressure along the eastern coast, which saw the minimum climb to 20.5 degrees in the last two days of November. The air cleared after that as the humidity level dropped and the mercury touched 16 degrees on Monday, only to rise again.