Thiruvananthapuram, the entire coastal areas of Kerala and southern coastal parts of Tamil Nadu are likely to experience a "Kalalakkadal phenomenon" - a sudden surge in the sea causing strong waves - by 11.30 pm on Monday, prompting the central agency to issue an alert. For fishermen and coastal residents.

According to the Indian National Center for Ocean Information Services (INCOIS), "As rough seas are likely to intensify, stay away from the danger area as per instructions of the authorities."

INCOIS, the agency that issues weather warnings to fishermen in the country, has advised people to tie up fishing vessels safely in the port.

"The risk of collision can be avoided by maintaining a safe distance between boats. The safety of fishing equipment must be ensured," it said in a statement here.

INCOIS also advised people to completely avoid beach trips and other activities.

The word 'Kalalakkadal' literally means a sea that comes suddenly like a thief.

INCOIS has said that this surge is the result of strong winds coming suddenly at certain times without any special signal or warning in the southern part of the Indian Ocean, hence it has been named "Kalalakkadal".