Extreme downpour in Chennai; Parrys records 36 cm rainfall

CHENNAI: An upper air cyclonic circulation over north Tamil Nadu and adjoining south coastal Andhra Pradesh enhanced wind convergence and moisture transport, fuelling deep cumulonimbus clouds that brought intense, widespread rainfall over Chennai and adjoining areas in the wee hours of Sunday.

The rainfall was so extremely heavy that Parry recorded 36 cm, followed by Kathivakkam with 34 cm, Chennai Central with 27 cm, and Tiruvottiyur and Ennore with 22 cm each in just 24 hours ending 8.30 am on Sunday.

According to the Regional Meteorological Centre (RMC), Chennai, an upper air cyclonic circulation lying over north interior Karnataka and its neighbourhood, and a low-pressure area formed over the southwest Arabian Sea on Sunday under the influence of an upper air cyclonic circulation over the same region, are likely to bring more rains in the coming days.

Surprised by the intensity of the rainfall, many described it as a cloudburst. However, not all experts concur. A cloudburst is conventionally described in India as 100 mm or more of rainfall within one hour over a small area of about 20 to 30 square km. Based on the observed rainfall pattern, the Chennai event appears to have resulted from organised, widespread convective activity linked to the cyclonic circulation, rather than an isolated, highly localised cloudburst, said weathermen.

Heavy rain was also recorded at several other places in and around Chennai. MGR Nagar recorded 19 cm, while CD Hospital in Tondiarpet and Perambur recorded 18 cm each. Tondiarpet logged 17 cm, and Vadapalani and the Chennai Collector Office recorded 16 cm each. Basin Bridge, Nungambakkam, YMCA Nandanam, Meenambakkam and Alandur recorded 15 cm each, while Ice House recorded 14 cm. Meenambakkam and Madhavaram received 13 cm each. Manali, Madipakkam, Manali New Town and Saligramam recorded 12 cm each, and Valasaravakkam, Gummidipoondi in Tiruvallur and Marakkanam in Villupuram received 11 cm each.

On Monday, heavy to very heavy rain with thunderstorms and lightning is likely at isolated places over Chennai, Tiruchy, Coimbatore and the Nilgiris districts, with gusty winds of 40-50 kmph at one or two places. Heavy rain with similar conditions is likely over Chengalpattu, Kancheepuram, Tiruvallur, Dharmapuri, Krishnagiri, Salem, Tirupur, Dindigul, Theni, Virudhunagar, Tenkasi, Tirunelveli, Kanniyakumari, Thoothukudi, Ramanathapuram, Madurai, Sivaganga, Pudukkottai, Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai, Cuddalore, Karur, Perambalur, Ariyalur, Villupuram, Vellore, Ranipet, Tiruvannamalai, Kallakurichi, Tirupattur, Erode, Namakkal, Puducherry and Karaikal area.

On October 21, heavy to very heavy rain is likely at isolated places over the Nilgiris, Coimbatore, Madurai, Theni, Kanniyakumari, Tirunelveli and Dindigul districts. Heavy rain is likely over Chennai, Kancheepuram, Chengalpattu, Erode, Namakkal, Salem, Tirupur, Virudhunagar, Tenkasi, Mayiladuthurai, Nagapattinam, Thanjavur, Tiruvarur, Pudukkottai, Tiruchy, Ariyalur, Perambalur, Sivaganga, Ramanathapuram, Thoothukudi, and Karur districts, and Karaikal area.

On October 22, heavy rain is likely at isolated places over the Nilgiris, Coimbatore, Tirupur, Dindigul, Theni, Virudhunagar, Tenkasi, Tirunelveli, Kanniyakumari, Thanjavur, Ramanathapuram, Madurai, Thoothukudi, Tiruvannamalai, Salem, Namakkal, Ariyalur, Perambalur, Tiruchy, Erode, Pudukkottai, Karur and Sivaganga districts.

The maximum temperature on Monday is expected to be 32 degrees Celsius, with the minimum dipping to 24 degrees Celsius.

According to RMC data, the northeast monsoon rainfall across the State between October 1 and October 18 was 18 per cent higher than normal, standing at 96.8 mm compared to the average 82.3 mm.