Chennai: The depression over southwest and adjoining southeast Bay of Bengal will intensify into cyclonic storm ‘Nivar’ and would cross the Tamilnadu and Puducherry coasts on Wednesday, resulting in extremly heavy rainfall in the State.

Met experts said the depression moved northwestwards and lay centred about 500 km south-southeast of Puducherry and 530 km south-southeast of Chennai.

It is very likely to intensify into a cyclonic storm ‘Nivar’ during the next 24 hours, move northwestwards and cross Tamilnadu and Puducherry coasts between Karaikal and Mamallapuram, about 55 km from here, on 25 November afternoon.

The Met office has issued a Red Alert for Tamilnadu, Puducherry and Karaikal on 25 November and yellow alert for today, tomorrow and Friday.

Under its influence, the rainfall activity is likely to increase over south peninsular India from today onwards with fairly widespread to widespread rainfall/thunderstorm activity over Tamilnadu, Puducherry and Karaikal from 24 to 26 November and over south Coastal Andhra Pradesh, Rayalaseema and Telangana on 25 and 26 November, a bulletin issued by the Met office on Monday said.

Isolated extremely heavy rainfall activity is also very likely over Tamilnadu and Puducherry the period.