The India Meteorological Department announced on Thursday that the cyclonic circulation over the south-west Bay of Bengal off the south Sri Lanka coast may not intensify into a low-pressure area. However, it would continue to bring rain of very heavy intensity over south Tamil Nadu and gradually cover north coastal and adjoining districts till November 29.
On Thursday, the IMD issued the red alert for Thoothukudi, Tirunelveli, Ramanathapuram, Pudukottai and Nagapattinam as these districts were expected to receive isolated extremely heavy rain. Torrential rain pounded Thoothukudi and Tirunelveli districts, inundating several areas and affecting life.
Thoothukudi recorded an extremely intense rain of 26 cm between 8.30 a.m. and 5.30 p.m. on Thursday. Thiruchendur in Thoothukudi district received nearly 18 cm; the Thoothukudi port, 15 cm; and Palayamkottai in Tirunelveli district, 10 cm.
On Friday, Kanniyakumari, Tirunelveli and Thenkasi may record heavy to very heavy rain at one or two places. While most other places are likely to get moderate rain, 10 districts, including Chennai, Madurai, Pudukottai, and Puducherry, may have to be prepared for heavy rain at isolated places.
Weekend rain
The rainfall may turn more intense in Kancheepuram and Tiruvallur districts on Saturday and Sunday. Heavy rain is likely to lash more than 15 districts, including the Cauvery delta districts, Chengalpattu, the Nilgiris, Salem, Erode and Puducherry, on Saturday. Chennai may experience heavy rain in some areas till the weekend.
Officials said the cyclonic circulation at the lower tropospheric levels and the strong north-easterly winds prevailing over the Tamil Nadu coast at the lower level would push moisture and rain clouds towards the State. S. Balachandran, Deputy Director-General of Meteorology, Chennai, said conditions were not favourable for the circulation over the Bay to consolidate and intensify further. The broad low would still influence the spell of heavy rain. The forecast largely remained the same and the rainfall pattern might vary at some places.
A trough line from the weather system along the coast extending up to the northern districts would also sustain the wet spell over Tamil Nadu till November-end. Sometimes, weather systems in initial stages as these would bring heavy rain, he said.
Asked why cyclonic circulation did not gain strength, officials said the pressure gradient force between the centre of the circulation and the surrounding areas was less and this decreased the wind speed. Moreover, the Sri Lanka land mass prevented wind speed from increasing further.
Another low pressure
Another low-pressure area is brewing. It is likely to form over the south Andaman sea around November 29. This may become more marked in the next two days. But it has to be monitored for its impact on Tamil Nadu, officials said.
The weather systems this season has yielded excess rain in Tamil Nadu, which recorded 54.1 cm until Thursday, 61% more than the its average of 34 cm.
