A deep depression forming over the Bay of Bengal is expected to bring widespread heavy rainfall, thunderstorms, and strong winds to Tamil Nadu, Puducherry, and Karaikal. The weather system, which intensified from a low-pressure area on January 5, is forecast to move west-northwestward and further develop over the southwest Bay of Bengal. Coastal and interior regions are anticipated to experience significant rainfall, with specific alerts issued for districts like Mayiladuthurai, Nagapattinam, Thanjavur, Tiruvarur, and Pudukkottai.