A low-pressure zone in the southwest Bay was steadily strengthening on Tuesday while shifting northwest.
The system turned into a well-marked low-pressure area by 8.30am on Tuesday, the Met office said.
“It is likely to move west-northwestwards and intensify into a depression over southwest and adjoining Westcentral Bay of Bengal off north Tamil Nadu and south Andhra Pradesh coasts by Wednesday afternoon,” said a Met bulletin.
“It is likely to continue to move west-northwestwards towards north Tamil Nadu, Puducherry and south Andhra Pradesh coasts and intensify further during the subsequent 24 hours,” the bulletin said.
Sustained intensification turns a depression into a deep depression and then into a cyclone.
On Tuesday, the Met office could not say whether this system would eventually turn into a cyclone.
A depression generates wind speeds ranging between 40kmph and 49kmph. For a deep depression, it ranges between 50kmph and 62kmph. A cyclone generates wind speeds of around 63kmph and above.
Cyclones feed on heat and moisture. May and October-November provide a conducive sea surface for the intensification of tropical storms on the Bay of Bengal.
However, there are other factors at play. A strong vertical wind shear, for example, is detrimental to the intensification of a cyclone.
Impact on city
Even if the system turns into a cyclone, it is unlikely to have much of an impact in Bengal, said a Met official.
No alerts are associated with the system for Bengal in the next five days.
Light to moderate rain is expected in Calcutta and several other places in the state between October 25 and 27, according to the Met forecast.
“But that will be more because of the change in wind patterns and a rise in moisture incursion from the Bay,” said the Met official.
The city was bright and sunny for most of Tuesday. Much of the day felt scorching. But a Met official said it was not abnormal.
The Met office recorded a maximum temperature of 33.9 degrees, a notch above normal. “The usual maximum temperature for late October is around 33 degrees. A degree up or down is not unusual,” he said.