Heavy rain has been forecast for today at isolated places over Tamil Nadu, Puducherry and Kerala as the North-East monsoon settled over the South Peninsula from this morning.
Thunderstorms accompanied by lightning have been warned over the southern parts of Konkan and Goa thanks to the presence of a cyclonic circulation in the neighbourhood.
The heavy rain forecast for Tamil Nadu, Puducherry and Kerala would stay valid through the next four to five days until October 31, the India Met Department (IMD) indicated.
Earlier in the morning, the IMD had declared that the North-East monsoon has established over Tamil Nadu, Puducherry, Kerala and adjoining parts of Andhra Pradesh and Karnataka.
The announcement came after the IMD convinced itself that the north-easterly winds had established along the East Coast to the required speeds and depth.
A cyclonic circulation each over South-East Tamil Nadu and the South-East Arabian Sea - though the latter is moving away from the coast - is expected to help sustain the easterly flows over the South Peninsula.
Satellite pictures in the afternoon showed a cloud build-up between Kerala and Karnataka on the West Coast and between Chennai and Kakinada on the East Coast.
Importantly, the Bay of Bengal side showed cloud formation in a continuum reaching right upstream to the Gulf of Thailand, where the North-East monsoon has already established.
In fact, the Thai Met Department said early this morning that the North-East monsoon is set to intensify over the lower South China Sea and adjoining Gulf of Thailand over the next few days.
It also indicated the presence of a low-pressure 'cell' in the lower South China Sea, which is expected to move into the Gulf before it crosses into the Andaman Sea/ South-East Bay of Bengal next week.
Most global models expect this to become a tropical cyclone in the East-Central Bay. Some of them said the storm would be snapped up by a passing western disturbance over North-East India.
But the European Centre for Medium-Range Weather Forecasts says the Andhra Pradesh-Odisha coasts too should be wary of the track the storm takes after November 5.
A US-based weather tracker suspects that a follow-up storm forming in the Bay could take aim at the North Tamil Nadu and adjoining South Andhra Pradesh coasts between November 8 and 12.