Vijayawada, Dec 11 (IANS): Authorities on Sunday sounded an alert in Andhra Pradesh and adjoining Tamil Nadu as cyclonic storm 'Vardah' over the Bay of Bengal has turned into a "very severe" one.

The storm is likely to cross north Tamil Nadu and south Andhra Pradesh coast by Monday afternoon, said Indian Meteorological Department on Sunday.

According to IMD, 'Vardah' over west central and adjoining south Bay of Bengal moved further westwards and lay centred at 530 hours over west central and adjoining southwest Bay of Bengal about 520 km east-southeast of Nellore, 490 km east-southeast of Machilipatnam and 480 km east-northeast of Chennai.

"The storm is very likely to move nearly west-southeastwards and maintain its intensity till Sunday evening. Thereafter it will weaken gradually while moving towards south Andhra Pradesh coast and adjoining north Tamil Nadu coast," the IMD said.

The Met office has forecast light to moderate rains at many places with isolated heavy to very heavy falls over south Andhra coast and north coastal Tamil Nadu from Sunday evening for subsequent 36 hours.

Light to moderate rains are likely to occur over north coastal Andhra.

Strong winds with speed of 40-50 kmph are likely along the coast from Sunday.

The speed may increase to 70-80 kmph at the time of landfall. Damage to thatched huts, power and communication lines, roads and crops is expected.

As the sea will be rough, fishermen have been advised not to venture into the sea for next 48 hours.

Authorities have hoisted third warning signal at all ports on Andhra coast.

District administration in Krishna, Guntur, Prakasam and Nellore have been alerted to take all precautionary measures.

Andhra Pradesh Chief Minister N. Chandrababu Naidu, who has cancelled his visit to the UAE and Kuwait, is monitoring the situation from the command and control centre in Vijayawada.

Naidu deputed four senior IAS officers to four districts to take necessary steps to minimise the loss of lives and property.

Two teams of National Disaster Response Force have reached Nellore district.