The northeast monsoon is expected to arrive in Tamil Nadu, bringing heavy rainfall to Chennai and 21 other districts, with a yellow alert issued

MADURAI/CHENNAI: Heavy rainfall over city and several other districts may mark the arrival of the northeast monsoon on Thursday. IMD has forecast heavy rain (yellow alert) of 6cm to 12cm in 24 hours in Chennai and 21 other districts, including Kancheepuram, Tiruvallur, Chengalpet, and very heavy rain (orange alert) of 12cm to 20cm in four southern districts. Private forecasters said much of the intense rainfall may be over interior districts, while coastal districts could see moderate rain for at least the next five days.“The northeast monsoon rainfall is likely to commence over Tamil Nadu-Puducherry-Karaikal, KeralaMahe, south interior Karnataka, south coastal Andhra Pradesh, and Rayalaseema during the next 24 hours,” said an IMD bulletin on Wednesday.The northeast monsoon is crucial for Tamil Nadu and Chennai, bringing 48% of the state’s annual rainfall and 63% of the city’s, about 45cm and 87cm respectively.On Thursday, the city and suburbs may receive a few spells of moderate to heavy rain with thunder and lightning over some areas. The maximum temperature may be around 31°C and the minimum between 24°C and 25°C.Between Oct 17 and 20, heavy rain activity is expected to shift to western and southern districts.Mahesh Palawat, chief meteorologist, Skymet Weather, said the heavy rainfall over interior Tamil Nadu may be due to an upper air cyclonic circulation over the Comorin area. “For the next four to five days, coastal areas may receive moderate intensity rain. This northeast monsoon season will bring good rainfall to Tamil Nadu,” he said.Since Oct 1, Chennai has recorded 7 cm of rainfall, around 5% below normal, while Tamil Nadu logged 9cm, about 34% above normal. Kancheepuram recorded 10 cm (34% above normal), Tiruvallur 9cm (34% above), and Chengalpet 5cm (34% below).