Weather system brews in Bay of Bengal; heavy rainfall warning for Chennai

According to the Indian Meteorological Department (IMD), a low-pressure area has formed in the South West Bay of Bengal, off the Sri Lankan coast on Saturday (15th Nov). In the coming days, the system is expected to move west-northwestward, causing rainfall along the Tamil Nadu coast.

In meteorology, a low-pressure area is one where the atmospheric pressure is lower than the surrounding areas. It is associated with cloud formation, increased humidity and rainfall. It causes moderate rain, cloudy skies. A depression is an intense low-pressure area that brings moderate to heavy rainfall, thunderstorms, and gusty winds.

For the weekend, a heavy rainfall warning has been issued for at least eight districts of Tamil Nadu. They include Mayiladuthurai, Nagapattinam, Tiruvarur, Thanjavur, Pudukottai, Ramanathapuram, Sivaganga, and Villupuram.

Owing to this weather system, rainfall has been forecast for several districts of coastal Tamil Nadu over the next few days. Notably, heavy rain is forecast for Chennai city and adjoining districts, and other coastal districts of Tamil Nadu on Monday, Tuesday. Rainfall activity in parts of Tamil Nadu is expected to continue until Wednesday, 19th November.

The period between mid-October and mid-December is the Northeast monsoon season which is the second major rainfall season in India, and is crucial for large parts of Tamil Nadu, Andhra Pradesh, Puducherry.

The Northeast monsoon caters for about 50% or more of the annual rainfall in Tamil Nadu and coastal Andhra Pradesh. This season is known for cyclonic storms or weather systems that form in the Bay of Bengal, which can lead to very heavy rainfall and potential flooding in parts of Tamil Nadu and coastal Andhra Pradesh. These rains are also crucial for recharging the water table and the reservoirs.