As per IMD Regional Metrological department, Under the influence of the cyclonic circulation over southeast Bay of Bengal & neighborhood, a low-pressure area has formed over the same region. Associated cyclonic circulation extends up to 4.5 km above mean sea level. It is very likely to concentrate into a Depression over Southwest & adjoining Southeast Bay of Bengal during next 36 hours. It is likely to move west–northwestwards and reach near north Tamil Nādu coast by the early morning of 11th November 2021. Yesterday’s trough now runs from the cyclonic circulation over southeast Bay of Bengal & neighborhood to Gulf of Mannar extending up to 5.8 km above mean sea level.
On 9th Nov 2021, Thunderstorm with Extremely heavy rain is likely to occur at isolated places over delta districts, Pudukkottai, Ramanathapuram and Karaikal area. Thunderstorm with Heavy to very heavy rain is likely to occur at a few places over Thenkasi, Tirunelveli, Thoothukudi, Cuddalore, Madurai and Sivaganga districts. Thunderstorm with heavy rain is also likely to occur at a few places over Chennai, Tiruvallur, Kancheepuram, Chengalpattu, Ariyalur, Perambalur, Tiruchirapalli, Villupuram districts and Puducherry. Moderate rain is likely to occur at most places over rest districts of Tamil Nādu.
On 10th Nov 2021, Thunderstorm with extremely heavy rain is likely to occur at isolated places over delta districts, Cuddalore, Villupuram, Pudukkottai, Sivaganga, Ramanathapuram and Puducherry & Karaikal. Thunderstorm with Heavy to Very heavy rain is likely to occur at a few places over Chennai, Tirunelveli, Kanyakumari, Thenkasi, Virudhunagar, Madurai, Ariyalur, Perambalur, Kancheepuram, Tiruvallur and Chengalpattu districts. Thunderstorm with Heavy rain is also likely to occur at a few places over Nilgiris, Coimbatore, Erode, Salem, Vellore, Ranipettai, Tirupattur, Tiruvannamalai, Thoothukudi, Kallakurichi and Karaikal area. Light to moderate rain is likely to occur at most places over rest districts of Tamilnadu.
Reference: http://imdchennai.gov.in/tn_fc.pdf
http://www.imdchennai.gov.in/hrw_district.htm