At a time when Chennai is still recovering from the impact of the previous downpour , the Meteorological Department has forecast a very heavy spell of rain over the city and its surrounding districts on Wednesday and Thursday.
A red alert has been issued for Chennai and its neighbouring districts — Tiruvallur, Kancheepuram and Ranipet — for Thursday. Extremely heavy rain, measuring above 20.4 cm, is likely in one or two places.
Officials of the Department said the low-pressure area over the Bay of Bengal, with an associated cyclonic circulation, persisted. It may move westwards and reach west-central and southwest Bay of Bengal, off south Andhra Pradesh and north Tamil Nadu coasts, on Thursday.
As the system begins to move towards the Tamil Nadu coast, the intensity of rain may go up. On Wednesday, rain may be heavy or very heavy in some places over the city, Tiruvallur and Kancheepuram. Delta districts, Puducherry and five other districts can expect heavy rain in one or two places. Many other places are likely to experience light to moderate rain till Saturday.
On Thursday, when the system nears to Tamil Nadu coast, rain may be extremely heavy in isolated places in Chennai and its neighbouring districts.
On Tuesday, Harur and Palacode in Dharmapuri district received 5 cm and 4 cm of rainfall, respectively, between 8.30 a.m. and 7.30 p.m., apart from many other weather stations. During the past 24 hours, ending 8.30 a.m. on Tuesday, Madukkur in Thanjavur district and Chettikulam in Perambalur district recorded heavy rain of 10 cm each.
S. Balachandran, deputy director general of meteorology, Chennai, said there was little chance for the low-pressure area to intensify.
There is also another low-pressure area over the Arabian Sea, and the interaction between the weather systems in the Bay of Bengal and the Arabian sea will induce heavy rainfall, he said. Both the systems will feed moisture into each other, and a trough line, running between the systems, will bring fairly widespread rain, and particularly over north Tamil Nadu, he said.