India, Aug. 20 -- Fishing communities along Kerala, southern Tamil Nadu and the Lakshadweep Islands are on alert after the Indian National Centre for Ocean Information Services (INCOIS) warned that a swell surge, locally known as Kallakkadal, could batter the coast on Thursday.

INCOIS, an autonomous body under the Ministry of Earth Sciences that tracks and forecasts ocean conditions during extreme weather, from high swells to storm surges, said high-period swells generated far out in the southern Indian Ocean have already reached Indian shores.

INCOIS's network of moored buoys and wave rider buoys - devices anchored to the seabed that measure surface wave activity - deployed along the southern coast confirmed the swell, feeding data int...