CHENNAI: North Chennai bore the brunt of an intense spell of rain on Saturday, with several neighbourhoods receiving over 150 mm in a few hours and two rainfall stations crossing the 300 mm mark since the onset of the northeast monsoon (NEM), the first such instance in Tamil Nadu this season.
Hourly rainfall data from the Greater Chennai Corporation’s Integrated Command and Control Centre and TN Disaster Risk Reduction Agency showed that Zonal Office 1 at Kathivakkam recorded the highest cumulative rainfall of 310.2 mm by midnight, with half of the total rainfall occurring within a one-hour period between 9.30 pm and 10.30 pm. Similarly, Parrys station also crossed 300.9 mm, followed by Sathangadu (234.4 mm). Thiruvottiyur recorded 198.6 mm, while Ennore and Kargil Nagar received 192.4 mm and 180 mm, respectively.
The rainfall intensified after 9 pm. A total of 26 weather stations, of which 20 are in Chennai, recorded over 100 mm. Chennai typically witnesses such rains towards the end of November and in December. The extreme rainfall is attributed to nearly stationary upper-air circulation over Chennai and intense thunderstorm activity. Several areas have reported waterlogging. According to the corporation, seven water-stagnation complaints were reported on Saturday, and most of them were cleared.
Orange alert issued for nine districts in TN
However, localised waterlogging was reported in Perambur and Thiruvottiyur, with officials expecting the affected locations to be cleared by Sunday morning.
Other affected stretches included Perambur High Road near Julian Nursing Home in Jamalia, areas near Perambur railway station, Perumal Koil Street in Kadirvedu, Bunder Garden in Perambur, Arthoon Road and Shaik Maistry Street in Royapuram, and parts of Navalur.
Weather blogger Pradeep John attributed the extreme rainfall spell to three factors: an upper-air cyclonic circulation (UAC) that kept winds converging over north Tamil Nadu and Chennai, unusually warm sea surface temperatures off the Tamil Nadu coast, and the heat that built up over the region during the preceding 25 rainless days, providing the energy needed for storms.
The Regional Meteorological Centre has forecast heavy rain at isolated places across several districts on Sunday, including Chennai, Tiruvallur, Chengalpattu, Villupuram, Cuddalore, Kancheepuram, Salem, Krishnagiri, and the Nilgiris. An orange alert has also been issued for heavy to very heavy rain at isolated places on October 20 in the Nilgiris, Coimbatore, Tiruppur, Dindigul, Theni, Tenkasi, Virudhunagar, Tirunelveli, and Kanniyakumari districts.
Meanwhile, an upper-air cyclonic circulation over the southwest Arabian Sea is likely to lead to the formation of a low-pressure area over the region by Monday.
In Erode, persistent rain contributed to the collapse of a nearly 60-year-old, three-storey private building on Subramaniyar Kovil Street on Saturday afternoon. The unused structure reportedly began tilting before collapsing onto the road, damaging a nearby electricity pole and temporarily disrupting power supply. No injuries were reported.