Cyclone Gaja presently centred over the Bay of Bengal is likely to weaken and cross the Tamil Nadu coast between Pamban and Cuddalore on Thursday forenoon, the Met said on Tuesday.
Before it weakens, there would be rough to very rough sea conditions along and off Tamil Nadu-south Andhra Pradesh coasts from Wednesday morning and high swelling sea during that night.
The fishermen, who were in deep sea have been asked to return to coasts immediately.
The Indian Meteorological Department (IMD) bulletin said Gaja has been moving westwards with a speed of five kmph in the past six hours.
At 5.30 a.m., the cyclonic storm was centred about 750 km east of here and 840 km east-northeast of Nagappattinam.
It was expected to intensify further into a severe cyclonic storm in the next 24 hours by Wednesday and maintain that intensity till Thursday. "It is very likely to move west-south-westwards," IMD said.
At the time of landfall, storm surge of height of up to one metre above astronomical tide was expected to inundate low lying areas of Nagappattinam, Thanjavur, Pudukkottai and Ramanathapuram districts of Tamil Nadu and Karaikal district of Puducherry, the IMD said.
It has advised total suspension of fishing operations along and off north Tamil Nadu and Puducherry and adjoining south Andhra Pradesh coasts during November 13 to 15.>