Chennai, Dec 19 (IANS): The Regional Meteorological Centre (RMC) has downgraded the heavy rainfall alert for Chennai and neighbouring districts, including Kancheepuram, Chengalpattu and Tiruvallur, for Thursday.

The latest forecast indicates that light to moderate rain is likely to occur in many parts of North Coastal Tamil Nadu and at isolated places in other parts of Tamil Nadu, Puducherry, and Karaikal.

The low-pressure area over the southwest Bay of Bengal has intensified into a well-marked low-pressure area.

It is expected to move northwestwards towards the north Tamil Nadu and south Andhra Pradesh coasts over the next 24 hours and subsequently move northwards along the Andhra Pradesh coast within the following 24 hours.

Tamil Nadu has recorded 14 per cent excess rainfall during the ongoing northeast monsoon season, with 447 mm of rainfall against an average of 393 mm.

Chennai registered 845 mm of rainfall, which is 16 per cent above average, while Coimbatore saw a significant 47 per cent increase.

Heavy rain since the onset of the northeast monsoon (October 1 onwards) brought Tamil Nadu's reservoirs close to full capacity.

The state's reservoirs are just 12 per cent short of their total capacity of 224.297 thousand million cubic feet (TMC).

The Tamil Nadu Water Resources Department (WRD) reported that 12 reservoirs (three in the Coimbatore region, seven in the Madurai region, and two in the Chennai region) have reached full capacity.

The WRD said that 18 reservoirs have storage exceeding 90 per cent of their capacity while 23 reservoirs have water levels between 70 per cent and 80 per cent.

The cumulative water storage across Tamil Nadu's reservoirs stands at 195.455 TMC, leaving it 24.824 TMC short of full capacity.

Heavy rain during the past two and a half weeks of the active northeast monsoon phase has significantly boosted water inflows into the state's 90 reservoirs, raising storage levels by 10.68 percentage points - from 76.46 per cent to 87.14 per cent.