The well-marked low-pressure area over Southwest Bay of Bengal (BoB) has moved west-northwest and come closer to the coastline of Sri Lanka and Tamil Nadu. The low pressure is located over Palk Strait and adjoining parts and is supported by the cyclonic circulation up to mid-tropospheric levels. The peripherals of the system have already reached the coastline and light to moderate rainfall was recorded at Karaikal, Puducherry, Parangipettai, Cuddalore and Chennai. The rainfall will pick up force and cover as the day progresses. Powerful rains are likely over the central parts of the coastline and moderate elsewhere.
The weather system will take about 48 hours to clear the state of Tamil Nadu and only the remnant effect will be observed later. Heavy to very heavy rains are expected over Thoothukundi, Nagapattinam, Ramanathapuram, Tondi, Pamban, Tuticorin, Karaikal and Parangipettai. The flanks on either side of this stretch will have moderate-intensity showers, embedded with isolated heavy spells for brief durations. Chennai, Tiruvallur, Chengalpattu, Kancheepuram, Tambaram and Puducherry will cover the northern flank and Palayankottai, Nagercoil and Kanyakumari will lie on the extreme southern side. These locations may escape the fury of incessant and blinding rains. Yet, utmost caution needs to be exercised till the threat gets over on 13th December.
Heavy rains in the coastal parts may derail normal life. Even the interiors are also likely to have scattered heavy spells. Madurai, Thanjavur, Trichy and Sivaganga also have to watch out for heavier bouts, more so, in the next 24 hours. Localized flooding of streets and roads in many places remains a possibility. Stormy conditions with heavy lightning, thunderstorms and strong winds will last between 11th and 12th December.
Rains will be rather mild on 13th Dec for the coastline and ease out significantly, a day later on 14th December. Another wave of weather activity can be expected between 16th and 18th December 2024. Many locations can expect rainfall in excess of 20 cm at many locations including Chennai and Puducherry during the entire episode.