The rain over the weekend was only the prelude. India Meteorological Centre has issued an orange alert for Tuesday (November 9) forecasting thunderstorms with heavy rain in the city and many districts triggered by a low pressure system.
The Nungambakkam weather station (city), with 141cm so far this year, has already surpassed its annual normal rainfall of 140cm, while Meenambakkam (132cm so far) is inching towards its quota of 138cm.
The rain forecast for November 9 may increase on November 10 and 11 with heavy to very heavy and isolated extremely heavy spells.
The city, private forecasters said, may get a break from heavy rain on November 9 before it picks up pace on November 10 and continues through November 11. For the next 48 hours, thunderstorms with moderate rain, heavy at times have been forecast over some city areas and the suburbs with the skies remaining generally cloudy. Maximum and minimum temperature will be around 26 degrees C and 24 degrees C.
“The system is approaching the coast as a depression,” said N Puviarasan, director of IMD’s Area Cyclone Warning Centre.
The low pressure area is likely to form under the influence of a cyclonic circulation over southeast Bay of Bengal and adjoining south Andaman Sea extending up to 5.8km above mean sea level. “It is likely to move west-northwestwards, concentrate into a depression and reach north Tamil Nadu coast by November 11 early morning,” IMD said.
IMD has forecast rain of varied intensity over some southern, interior and delta districts on November 9. Intensity may increase on November 10 and 11 with rainfall ranging from extremely heavy to heavy over many parts of the state including Chennai and neighbouring districts.
On Monday, Nungambakkam and Meenambakkam recorded 14.5mm and 14.8mm till 7.30pm. The northeast monsoon has so far left 632.2mm and 520.4mm in the two stations since October 1, an excess of 226.4mm and 116.9mm. Tamil Nadu recorded 346.1mm against a normal of 241.2mm in the same period. Chennai subdivision registered 547.9mm against 392.5mm (40% excess), while neighbouring Kanchipuram recorded 17%, Tiruvallur 31% and Chengalpet 34% excess.
Mahesh Palawat, Skymet Weather chief meteorologist, tweeted that Chennai got 415mm between November 1 and 8, against the average of 374.4mm for November, the wettest for Chennai.
Blogger Pradeep John said models showed the system may move a few hundred kilometres into the land before losing strength. “There won’t be any break in rainfall. We will continue to receive rain even after the system fizzles out because of weak northeasterly winds. But they may be mostly light spells,” an IMD official said.