A red alert indicates a downpour of over 204.4 millimetres in 24 hours; Chennai received 215 mm rainfall on November 7
Chennai received 215 mm rainfall on November 7, the second-highest 24-hour rainfall during the decade. Photo: Twitter / @ChennaiRains
The India Meteorological Department (IMD) has issued a red alert for Chennai and five other districts of Tamil Nadu from November 10-12 morning, indicating heavy to extremely heavy rainfall in the city and surrounding areas owing to the northeast monsoon.
A red alert indicates a downpour of over 204.4 millimetres in 24 hours.
The city saw heavy to very heavy rainfall on November 7. Chennai received 215 mm rainfall in one day, the second-highest 24-hour rainfall during the decade, according to Skymet Weather.
The highest ever 24-hour rain recorded was 452.6 mm witnessed on November 25 in 1976.
Four stations reported ‘very heavy’ rainfall and 23 stations reported heavy rainfall, according to 24-hour accumulated rainfall data as of November 8 morning.
The intensity came down later during the day.
The five districts the IMD issued a red alert for from 8:30 am on November 11 include Tiruvallur, Kancheepuram, Chengalpattu, Viluppuram and Cuddalore.
It issued a red alert on November 10 for Kallakurichi, Cuddalore, Perambalur, Ariyalur, Mayiluduthurai, Tiruvarur, Thanjavur and Nagapattinam, and Karaikal.
During this extremely heavy spell over Tamil Nadu, southern parts of coastal Andhra Pradesh may also see extremely heavy rainfall. Besides, adjoining sub-divisions of Kerala and Rayalaseema may also see isolated heavy rainfall on one or two days. Kerala is likely to receive isolated heavy rainfall during the next five days, an IMD briefing said November 8.
A low-pressure area is likely to form over southeast Bay of Bengal, which will intensify into a depression and will move towards Tamil Nadu coast, according to forecast by IMD.
The cyclonic circulation over southeast Bay of Bengal and adjoining south Andaman sea, extending up to 5.8 km above mean sea level, persisted there at 8:30 am November 8.
“Under its influence, a low-pressure area is very likely to form over south east Bay of Bengal and neighbourhood during next 24 hours. It is likely to move west-northwestwards, concentrate into a depression and reach near north Tamil Nadu coast by the early morning of November 11,” the IMD said.
This will lead to another spell of heavy to very heavy rainfall over Chennai and nearby areas on November 10 and 11.
Meanwhile, according to media reports, the Karaikal and Chennai radars of the meteorological department have gone offline due to technical snags. This has made nowcasting difficult in this cyclone season.
The IMD also advised the fishermen not to venture into areas in east central and adjoining west central Arabian sea.
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