IMD forecasts relief in Chennai rains from Thursday night; toll rises to 12

Red alert in 20 districts, with Chennai already having surpassed average rainfall in November during the first week of the month itself

Even as the death toll due to rain-related incidents in Tamil Nadu rose to 12, the India Meteorological Department said on Wednesday that the low-pressure area over southeast Bay of Bengal is likely to concentrate into a depression and move towards the North coastal region of Tamil Nadu giving a relief to heavy rainfalls by Thursday night.

A red alert is in place on Thursday in 20 districts of the state, as Chennai has already surpassed the average rainfall in November during the first week of the month itself. Nungambakkam Observatory has recorded a total of 464 mm of rain from November 1-9, while Minambakkam reported 369 mm against the normal of 374 mm.

“Right now the low pressure mark is there. It is likely to concentrate into a depression by today and may move towards North Coastal Tamil Nadu by Thursday morning and by evening will cross Karaikal and Cuddalore. Maybe tomorrow night we may see gradual relief for heavy rains in the state," said S Balachandran, deputy director general of Meteorology in Chennai, told Business Standard. Around 13 National Disaster Response Force (NDRF) teams are already deployed in the state with five teams focussing on Chennai.

According to Climate Trends, a Delhi-based climate communications initiative, although meteorologists have ruled out any direct linkage between the ongoing heavy rains in Chennai and adjoining areas with climate change, its contribution cannot be negated completely. It added that the coming together of three oceanic parameters-–La Nina, Indian Ocean Dipole (IOD) and MJO (Madden–Julian oscillation)-–caused the current torrential rains in Chennai and Andhra Pradesh. Around 215 mm of rainfall on November 7 is so far the second highest rainfall recorded in the span of 24 hours in the last decade, with the highest being 246.5 mm received on November 16, 2015. Meanwhile, the all-time record for 24 hours rainfall stands at 452.4 mm recorded on November 25, 1976.

“Rise in global temperatures has increased the frequency of heavy rains. The Indian Ocean is warming at a faster rate, with sea-surface temperatures (SST) soaring above average. 26.5°C is the threshold value, past which the conditions are very favourable for cyclogenesis or rapid intensification of any weather system,” a note by Climate Trends said. It added that global warming has increased sea level rise by 10 per cent to 15 per cent across the Indian seas and this coupled with heavy rainfall can amplify the damage in the region.

Chief Minister M K Stalin had blamed the erstwhile AIADMK government for the current waterlogging in the city, citing corruption in the implementation of the smart city project and Central schemes. This came after the High Court criticised the Chennai Corporation over not acting to solve the waterlogging issue for the last six years.