Freak weather dumped widespread, unprecedented extremely heavy rain in 39 places in southern districts, the highest being 95 cm in Kayalpattinam in Thoothukudi district. An upper air circulation dumping such a mind-boggling amount of rain in 24 hours was rare in the region, meteorology experts said.
While questions were raised on insufficient forewarnings about the extremely heavy rainfall in the region on Sunday (December 17), officials of the Regional Meteorological Centre (RMC) said they had warned of the probability of very heavy rains since December 14. The forecast was upgraded to extremely heavy rains (which is above 21 cm) in isolated places, ahead of 24 hours. However, the downpour was intense and widespread in southern districts particularly in Tirunelveli, Thoothukudi and Theni.
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Even as Chennai and neighbourhood are struggling to return to normalcy, torrential rain pummelled southern districts on Sunday. During the past 24 hours ending 8.30 a.m. on Monday, 39 places recorded extremely heavy rain, 33 places received very heavy rain up to 20 cm and 12 registered heavy rain.
Besides Kayalpattinam that received a whopping amount of rain, Tiruchendur and Srivaikuntam in Thoothukudi district received 69 cm and 62 cm of rain respectively. Some of the other places that recorded intense downpour include Moolaikaraipatti (61 cm), Manjolai (55 cm) - Tirunelveli district; Kovilpatti in Thoothukudi (53 cm), Gundar Dam in Tenkasi district (51 cm), Oothu (50 cm), Nalumukku (47 cm) and Ambasamudram (43 cm).
Tiruchendur -Thoothukudi belt that normally has a semi-arid climate received its annual rainfall in a day. Palayamkottai that had recorded 44 cm of rainfall had previously registered 20 cm of rain on December 10, 1931.
Variability of weather phenomenon
S. Balachandran, Additional Director General of Meteorology, Chennai, said the RMC gave forecasts in rainfall range and red coloured warning was provided for areas where rains were expected to be above 21 cm. “The exact amount of the rainfall expected is not given as of now due to limitations and variability of the weather phenomenon and science. Majority of international practices also don’t specify amount and prefer only rainfall probability range,” he said.
A weak weather system like an upper air circulation is not expected to bring such enormous amount of rain during north-east monsoon. Multiple factors helped the slow-moving weather disturbance that remained stagnant near Comorin area bring torrential downpour over southern districts. It moved at a speed of 4 km from Sri Lanka to Comorin area. Besides good moisture influx, lower level convergence of winds, divergence at upper level and equatorial Rossby waves that moved in the region also aided the extreme weather event.
“With climate change, we have to prepare for such extreme rainfall events in southern peninsular region during the north-east monsoon,” he said.
Tamil Nadu’s rain deficit, changed to 5% excess overnight. The RMC has forecast heavy rain to continue in Kanniyakumari, Tirunelveli, Thoothukudi and Tenkasi on Tuesday, December 19, 2023.
