Indian Meteorological Department has said that there will be isolated, extremely heavy rainfall over most places in Tamilnadu and Puducherry during Tuesday and Wednesday.
Experts said that the rainfall is triggered by Cyclone Nivar which is likely to make landfall between Mamllapuram and Karaikal on Wednesday noon or afternoon.
An IMD bulletin said a well-marked low pressure in the Bay of Bengal closer to the Tamilnadu coast will intensify into a depression in the next 12 hours and will develop into a cyclonic storm in the subsequent 24 hours.
The well-marked low pressure is located 760km away from Chennai and 700km from Karaikal. It will skirt the coast of Sri Lanka and move northwest to hit the Tamil Nadu coast.
A Met official said the system is moving at a good speed and has been named as cyclone Nivar by Iran. Private weather bloggers hint that conditions such as wind shear, warm sea surface temperature and absence of dry air are in favour of the cyclone to intensify.
However, the speed at which it will move and also develop can be a drawback, making it less intense. It is moving at 18kmph speed towards the coast.
Monday will be generally cloudy with light drizzle as the weather system is too far away and it will start raining of Tuesday as the cyclone edges closer to the coast. Villupuram, Cuddalore, Puducherry and Chennai are expected to have heavy rain when it starts to make landfall on Wednesday.