A speck over the South Andaman Sea is expected to gain strength and move northwest in the coming days, the Met office has said.

Weather scientists will keep a keen eye on the system because the period from the middle of October to the middle of November is known as the cyclone season.

May and October-November — pre and post monsoon periods — are favourable for cyclonic storms because the sea surface temperature is on the higher side. A weather system draws on the heat and moisture to gain strength over the sea.

“An upper-air cyclonic circulation lies over the South Andaman Sea and adjoining southeast Bay of Bengal sand extends up to 1.5km above mean sea level. Under its
influence, a low-pressure area is likely to form over the southeast Bay of Bengal around October 21,” said a Met report.

“It is likely to move west-northwest and intensify further into a depression over the central parts of south Bay of Bengal and adjoining west-central Bay of Bengal during the subsequent 48 hours,” said the report.

A depression intensifies into a deep depression before turning into a cyclone.

A Met official in Calcutta said it was still too early to predict the outcome of the system.

“For now, the impact of the system will be on Tamil Nadu and adjoining areas. We are tracking it continuously. A clearer picture will emerge in a couple of days,” he said.

This time last year saw Cyclone Dana, which triggered heavy rain in Calcutta after making landfall in Odisha on October 25.