A cyclonic circulation over the Bay of Bengal is intensifying and being monitored round-the-clock by the India Meteorological Department, while south Bengal is expected to remain dry until October 26 before light rain and thundershowers arrive over the following two days.
The weather system was located over the southeast and adjoining eastcentral Bay of Bengal at 8.30am on Thursday after moving west-northwestward from the north Andaman Sea, off the Andaman Islands. A Met report said a low-pressure area was likely to form over the same region on Friday under the system’s influence, after which it was expected to move west-northwestward and intensify further.
The Met office has not yet determined whether the system will develop into a cyclone. A Calcutta-based Met official said there was a “medium probability” of the system becoming a depression. A depression can intensify into a deep depression and subsequently into a cyclone, although several systems weaken before reaching cyclone strength.
“The upper-air cyclonic circulation over the north Andaman Sea, off the Andaman Islands, moved west-northwestward and lay over the southeast and adjoining eastcentral Bay of Bengal at 8.30am on Thursday. It is very likely to move west-northwestward and under its influence a low-pressure area is likely to form over the southeast and adjoining eastcentral Bay of Bengal on Friday. Then, it is likely to move west-northwestward and intensify further,” the Met report said.
For south Bengal, the immediate forecast points to a limited change in weather rather than a confirmed severe-weather event. “Dry weather is most likely to prevail over all the districts of south Bengal till October 26. As of now, light rain is likely on October 27 and 28. By October 26, the system is expected to approach land,” the official said.
The forecast is relevant to Kolkata, where weather conditions have remained sunny and dry in recent days. The city has also experienced a slight nip in the air at night, with less need for fans during the early morning. If rain arrives, the maximum temperature is likely to fall, while the minimum temperature may rise, according to the Met official.
The Bay of Bengal is particularly active during the early summer and post-monsoon months, when sea-surface conditions provide heat and moisture that can support the intensification of tropical storms. However, the Met official said other atmospheric conditions also influence a storm’s development. Strong vertical wind shear, for instance, can hinder cyclone intensification.
The region has recently seen the urban consequences of a Bay system that strengthened into a deep depression before making landfall in Andhra Pradesh on September 23. After moving towards Odisha and Chhattisgarh, that system triggered heavy rainfall in Calcutta. The Met office’s current assessment does not establish that the new system will follow the same track or produce similar rainfall.
The next official indications are expected as the low-pressure area forms and the system’s movement towards land becomes clearer. Until then, the Met office is maintaining close watch, with south Bengal’s forecast currently pointing to dry weather through October 26 and possible light rain on October 27 and 28.
