CHENNAI: The Regional Meteorological Centre has issued orange alert for Chennai, Thiruvallur, Kancheepuram and Chengalpattu.

Heavy to very heavy rainfall can be expected in these districts on Thursday. Other districts remain on yellow alert and heavy rainfall is expected in other areas.

The Regional Meteorological Centre officials said that the deep depression prevailing over the Bay of Bengal and adjacent South Andaman Sea areas moved in the west-northwest direction and prevailed over the Southeast Bay of Bengal on Thursday morning.

"The depression is expected to move in west-northwest direction and may intensify into a depression during next 24 hours. It will move further in West-Northwest direction and may intensify into a cyclone over Southwest Bay of Bengal by December 3rd. After that it will move in northwest direction and move towards the North East- South Andhra coastal areas on December 4th. We are trying to understand if it will weaken or strengthen further on December 4th," said Dr S Balachandran, Deputy Director-General of Meteorology of Regional Meteorological Center.

Under the prevailing weather conditions, heavy rainfall can be expected in the Chennai and neighbouring districts until December 4th. Among other districts, Thoothukudi, Ramanathapuram, Pudukottai, Thanjavur, Thiruvarur, Nagapattinam, Mayiladuthurai, Cuddalore, and Villupuram are likely to receive heavy rain until December 2nd.

Besides these districts, Thanjavur, Pudukottai, Ariyalur, Perambalur, Sivagangai, Vellore and Ranipet are also likely to receive heavy rains on December 3rd and December 4th. In the past 24 hours until Thursday, Thiruvallur received the highest amount of 19 cm of rainfall, followed by 15 cm in Chennai and 14 cm in Nagapattinam.

Meanwhile, the water outflow from Chembarambakkam lake that was initially at 6,000 cusecs in the morning, was reduced to 4,000 cusecs in the afternoon. The lake is currently at above 89 percent storage.