The prolonged dry spell over Tamil Nadu is expected to ease in the coming days as an unusual weather system over the Bay of Bengal has intensified into a deep depression. Meteorological officials have forecast scattered to heavy rainfall across several parts of the State, particularly along the coast, for at least three days beginning Friday, January 9.
According to the Regional Meteorological Centre (RMC), Chennai, the deep depression is currently positioned over the southwest Bay of Bengal and the adjoining east Equatorial Ocean. It is located approximately 810 kilometres southeast of Karaikal and about 980 kilometres south-southeast of Chennai. The system is likely to move west-northwestwards and cross the Sri Lanka coast between Hambantota and Kalmunai by Friday evening or night.
Meteorologists have described the system as rare for this time of the year. Historical records show that since 1891, the Bay of Bengal has witnessed only 20 intense weather systems during January, underscoring the unusual nature of the current development. While such systems are not unprecedented, they occur infrequently during the winter months.
B. Amudha, Head (Additional In-charge) of the RMC, said that although January systems have formed in the past, they are typically short-lived and less intense. The present deep depression, however, is expected to trigger heavy rainfall in parts of south coastal Tamil Nadu as it tracks close to the region.
The RMC has issued orange and yellow weather alerts for several districts, warning of intense rainfall that could reach up to 20 centimetres in isolated areas. On Friday, heavy to very heavy rain is likely over delta districts and parts of south coastal Tamil Nadu. Tiruvarur and Nagapattinam are expected to receive heavy to very heavy rainfall, while Ramanathapuram, Pudukottai, Mayiladuthurai and Thanjavur may witness heavy showers.
Rainfall is expected to become more widespread on Saturday, January 10, affecting several coastal districts as well as some interior regions. Intense rainfall may occur along the coastal stretch between Chengalpattu and Ramanathapuram. Districts such as Cuddalore and Tiruvarur are likely to receive heavy to very heavy rainfall, while heavy rain may occur in isolated places across districts including Pudukottai, Chengalpattu and Ariyalur.
Explaining why the system is considered rare, Y.E.A. Raj, former Deputy Director General of Meteorology, Chennai, said the current depression is comparable to the January 2023 system that crossed Sri Lanka’s east coast. He noted that between 1961 and 2024, only 11 intense weather systems formed over the Bay of Bengal during January, most of which were short-lived and did not cross the Tamil Nadu coast. Only two January systems, in 1967 and 2005, intensified into cyclonic storms.
Meanwhile, the RMC has also forecast the possibility of ground frost in higher elevations of the Nilgiris and Kodaikanal hills on Friday, as cold and dry conditions persist over the interior regions.
The evolving weather situation is being closely monitored, with officials urging residents in vulnerable districts to remain alert and follow advisories issued by local authorities.