CHENNAI: The deep depression, a remnant of Cyclone Ditwah, over the southwest Bay of Bengal has recurved towards the south and moved southeast, inching closer to the East Coast. This movement has prompted a red alert for four northern Tamil Nadu districts. The India Meteorological Department (IMD) on Tuesday warned of extremely heavy rainfall over Chennai, Kancheepuram, Chengalpattu, and Tiruvallur until 10 am.Read also: Cyclone Ditwah Live UpdatesAccording to the IMD, the weather system is now positioned at a minimum distance of about 35 km from the north Tamil Nadu–Puducherry coasts. “It is very likely to recurve slowly southwestwards and weaken into a depression during the next 12 hours,” the department said.Parts of north and central Chennai recorded heavy rainfall in the past 24 hours. Nungambakkam registered 17.1 cm, followed by Ennore with 16.6 cm, Puzhal 15 cm, and Nandanam 12 cm. South Chennai remained relatively less affected, with Meenambakkam receiving 8.5 cm.Weather blogger Pradeep John (Tamil Nadu Weatherman) said the system remained close to the Chennai coast for nearly 24 hours, resulting in intense rainfall in parts of Chennai and Tiruvallur. “It is expected to remain close to the Chennai coast for the next 18 hours and then cross the coast south of Chennai around the Kalpakkam belt this evening or night as a weakened system,” he said.John noted that since the system did not move north of Chennai’s latitude, cloud bands continued to stream over the city. He added that moderate rainfall was likely over Madurai, Virudhunagar, Sivagangai, Pudukkottai, the Delta districts, and isolated pockets of Puducherry, Cuddalore, and Villupuram. Ranipet and Tiruvannamalai are expected to receive rain once the system makes landfall.