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Chennai rain: low-pressure area forms over the Bay of Bengal, schools shut in four districts, more rain due
A low-pressure area formed off the Tamil Nadu coast early on Wednesday, and Chennai saw up to 15 cm of rain overnight. Schools are shut in four districts, 27 districts are under warning, and the department expects more rain through Friday.
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A low-pressure area has formed over the south-west Bay of Bengal, close to the Tamil Nadu coast, and Chennai has already paid for it. Up to 15 cm of rain fell on the city overnight, trees came down, streets flooded and schools were shut in four districts. The India Meteorological Department says more is coming, and a regional bulletin has put 27 districts under warning.
The department's Chennai centre said the low formed at 5:30 am IST on Wednesday, 21 October, and was still there at 8:30 am. It grew out of the previous day's upper-air cyclonic circulation off the Tamil Nadu coast, which extends up to 5.8 km above sea level. The trough that had stretched towards north coastal Andhra Pradesh has become less marked. The northeast monsoon, the department says, remains active.
Heavy to very heavy rain began on Tuesday and continued through the night. In the 24 hours to 8:30 am on Wednesday, MGR Nagar in Chennai recorded the highest total, 15 cm, and several neighbourhoods in and around the city received 10 to 15 cm. Catchment areas of the city's reservoirs, including Poondi, Cholavaram, Puzhal and Chembarambakkam, got up to 6.1 cm. Thudiyalur in Coimbatore, Sivagiri in Tenkasi, Pamban in Ramanathapuram and Rajapalayam in Virudhunagar each had 5 to 6 cm. The rain eased in Chennai by the afternoon and turned intermittent elsewhere. In the department's own scale, heavy rain means 64.5 to 115.5 mm in 24 hours and very heavy rain 115.6 to 204.4 mm, so MGR Nagar's 15 cm, or 150 mm, falls in the very heavy band. The department advised residents to remain alert.
Water stood on Taramani and the OMR stretch and in several parts of downtown T Nagar, and trees were uprooted in several areas. The Greater Chennai Corporation sent tractor-mounted pumps to Perungudi and Manali, cleared clogged causeways and channels, and said 78,161 branches had been cut and cleared as of Tuesday. It served 37,600 food packets through 103 cooking centres on Wednesday and opened camps in every zone to screen for and treat fever. Minister N Anand and Chennai Mayor R Priya inspected the work with officials. Schools were closed in Chennai, Thiruvallur, Kancheepuram and Chengalpattu. In Thoothukudi, saltpans flooded.
What the forecast says
The regional centre warned of heavy to very heavy rain at isolated places over Chennai, Thiruvallur, Chengalpattu, Cuddalore, Villupuram, Thanjavur, Thiruvarur, Nagapattinam, Mayiladuthurai and Ramanathapuram, and over Puducherry and Karaikal. A separate list of 27 districts, from Ariyalur to Vellore, was told to expect rain of a lighter kind, so the two headlines do not always match; the warning for each district should be checked against the latest bulletin.
For Thursday, 22 October, the department expects heavy to very heavy rain at isolated places in Thoothukudi, Tirunelveli, Kanyakumari, Tenkasi, Virudhunagar, Ramanathapuram, Theni, Dindigul, Madurai, Coimbatore, the Nilgiris, Sivaganga, Pudukkottai, Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai and Karaikal, with thunderstorms, lightning and gusty winds of 40 to 50 km an hour at one or two places. Friday, 23 October, brings widespread rain, with heavy to very heavy falls at isolated places over Kanyakumari, the Nilgiris and Coimbatore.
Pradeep John, a member of the state government's El Nino expert group, said the rain was likely to ease in Chennai during the day, with sunshine possible as the cloud moved north towards the Ponneri and Pulicat area. "Moderate to heavy rain is likely tonight and early in the morning," he said, and scattered showers could continue.
Beyond Friday
The department has not changed its wider outlook. Its earlier forecast said a low-pressure area would form, that it could become a depression over the central Bay of Bengal by 27 October and that it might grow into a cyclonic storm crossing north coastal Andhra Pradesh and south Odisha by the end of the month. The department has named no landfall point, and the system is still a low-pressure area, not a depression. For now the story in Tamil Nadu is rain, not a cyclone.
For residents the useful measures are the plain ones: avoid low-lying roads and underpasses after heavy rain, keep an eye on school and office notices in your district, stay away from fallen wires and trees, and look at the daily bulletin from the Chennai regional centre before travelling.
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4 min
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