Though Chennai recorded 14% excess rainfall in Oct, it has escaped major flooding so far. Even when the outer rain bands of severe cyclonic storm Murasu brought intermittent heavy rain on Sunday, the spells didn’t trigger widespread waterlogging. Corporation workers managed to pump out water at affected places by Monday morning. But meteorologists say the most challenging phase is yet to come.Murasu brought heavy rain over north and central Chennai on Sunday night, while the rest of the city received lighter spells. Kadapakkam and Parrys recorded 15cm each, followed by Manali and Manali New Town with 14cm. Ennore, Madhavaram and Tiruvottiyur received 10cm each. Of the 22 subways within Greater Chennai Corporation (GCC) limits, only Ganesapuram subway reported waterlogging. Waterlogging on Prakasam Salai, GP Road, Dr Alagappa Road and Sanjeeva Rajan Koil Street was also cleared. On Monday, Nungambakkam received 8.8mm and Meenambakkam 3.5mm till 7.30pm, while Puzhal recorded 25mm.GCC officials said preparation and quick deployment of pumps helped prevent widespread flooding. The civic body desilted 1,670km of stormwater drains and 81km of canals, besides pruning 78,161 trees. Its drainage network is designed to handle rainfall of up to 70mm an hour.“These are the first spells in this monsoon. We must be more vigilant as it advances, since heavy downpour in a short span has been the pattern. Tonight, we are preparing for another heavy spell of rain and possibly strong winds in north Chennai,” GCC commissioner G S Sameeran said.Rain may ease on Tuesday after Murasu crosses the Andhra Pradesh coast. Chennai is likely to receive light to moderate rain, with thunderstorms and lightning in some areas.But the city’s peak rainfall activity is still ahead. Nov is Chennai’s wettest month, averaging about 37cm. Though the IMD’s long-range forecast indicates below-normal rainfall in Tamil Nadu, including Chennai, individual weather systems remain difficult to predict.V R Durai, director of the Area Cyclone Warning Centre at RMC Chennai, said easterly waves — elongated low-pressure areas moving east to west — could bring widespread moderate to heavy rain from Nov 7. “There are chances for weather systems to develop one after another in the second half of Nov and Dec as the sea surface is warm. Usually, systems that develop at the end of Nov and early Dec move towards Chennai. So, there is a chance for Nov to end with excess rainfall,” he said.IMD director general Mrutyunjay Mohapatra said three of the four or five cyclones affecting India annually typically form during the northeast monsoon. “So one cyclone or depression can bring excess rain. It could bring the entire season’s rainfall. But the prediction of such weather systems will not be accurate in the long-range forecast bulletin and seasonal forecasts we issue at the beginning of a monsoon season or every month,” he said.
