IMD flags twin low pressure systems, warns of extreme rain in Tamil Nadu and Kerala

The India Meteorological Department (IMD) on Tuesday warned of "extremely heavy rainfall" over Tamil Nadu and Kerala as two well-marked low-pressure systems-one over the southeast Arabian Sea and another over the southwest Bay of Bengal-intensified under the influence of the northeast monsoon.

In an alert posted on X, IMD said: "Weather Warning! Two Well-Marked Low Pressure Areas one over the southeast Arabian Sea and another over the southwest Bay of Bengal are likely to bring heavy to very heavy rainfall (7–20 cm) across South Peninsular India (Oct 21–24). Extremely heavy falls (≥21 cm) expected over Tamil Nadu (Oct 21–22) and Kerala (Oct 22)."

Rain lashed several districts of Tamil Nadu on Tuesday. Chief Minister M K Stalin reviewed the situation with officials and instructed immediate precautionary measures. 

B Amudha, Director of the Regional Meteorological Centre (RMC), Chennai, said the low-pressure system over the Bay of Bengal had intensified into a well-marked low-pressure area located approximately 400 km from Chennai. "By noon tomorrow, there is a possibility that the system will strengthen into a Depression. This is expected to occur off the coasts of north Tamil Nadu, Puducherry, and south Andhra Pradesh," she said.

Explaining the evolving system, Amudha noted: "While intensification up to the deep depression stage is forecast, the possibility of it developing into a cyclone or storm can only be stated with some certainty after it has become a depression. Right now, the system that was a Deep Low-Pressure Area over the southeast Arabian Sea on October 20 is persisting with the same intensity."

According to her, a red alert was issued for eight districts—Villupuram, Cuddalore, Mayiladuthurai, Nagapattinam, Tiruvallur, Thanjavur, Pudukottai, and Ramanathapuram—while an orange alert was sounded for Chennai. Similar alerts were issued for the Union Territory of Puducherry.

Amudha added that "Chennai recorded an average of 60mm rainfall today, with a high of 100mm in Medavakkam." Between October 1 and October 21, Tamil Nadu, Puducherry, and Karaikal recorded 160mm rainfall—59 per cent higher than the normal average of 100mm for the same period.

Fishermen have been advised not to venture into the Arabian Sea, Bay of Bengal, and South Andaman Sea from October 23 to 26, as "squally winds reaching speeds of 45–55 km/h, gusting up to 65 km/h, are expected."

For October 22, IMD forecast "extremely heavy rain in four districts—Chengalpattu, Villupuram, Cuddalore and Mayiladuthurai—as well as Karaikal and Puducherry. Orange alert for Chennai tomorrow, too," Amudha said.