CHENNAI: The northeast monsoon gathered pace on Tuesday as a low-pressure area over the Bay of Bengal quickly intensified into a well-marked low pressure area, bringing intermittent light to moderate rain over coastal and adjoining districts, including Chennai.The intensity is likely to increase on Wednesday, with IMD issuing a red alert for extremely heavy rainfall (more than 20cm in 24hours) in four north TN districts, including Chengalpet, and an orange alert for heavy to very heavy rainfall (12-20cm in 24hours) in 11 north and delta districts, including Chennai, Tiruvallur and Kancheepuram, on Wednesday. The orange alert may continue for Chennai, Tiruvallur, Kancheepuram and Ranipet districts, along with Chengelpet, on Thursday.

B Amudha, deputy director general (addl charge), Regional Meteorological Centre, Chennai, said the system, hovering off the north Sri Lankan coast as on Tuesday evening, may strengthen into a depression over the southwest and adjoining west-central Bay of Bengal off north Tamil Nadu and south Andhra Pradesh coasts by Wednesday afternoon, and may move towards the north TN-Puducherry-south AP coast before intensifying further.“There is a chance for the system to intensify into a deep depression. Once it becomes a depression on Wednesday, we will know if it can develop into a cyclone,” she said.

‘Low pressure unlikely to intensify into cyclone’

“The pressure gradient will also determine its track, as the system will move towards regions of lower pressure,” said B Amudha, deputy director general (additional charge), Regional Meteorological Centre.On Wednesday, the city and suburbs may receive intermittent spells of moderate to heavy rainfall with thunderstorms and lightning in some areas. The sky may be generally cloudy. Maximum and minimum temperatures are likely to be around 28°C and 24°C-25°C.

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Chennai RainsWeather blogger Pradeep John said the system may approach the north TN coast on Wednesday morning, bringing heavy rain to Chennai, but is unlikely to intensify into a cyclone. “The next low-pressure system is expected around Oct 25-26, which may have a better chance of developing into a cyclone,” he said in an online post.Till 7.30pm Tuesday, rain gauges in Nungambakkam recorded 6cm of rainfall, Meenambakkam 4cm, Pamban 5cm, Tiruvarur 5cm, VIT Chennai 5cm, Kulithalai in Karur 5cm, ACS Medical College in Kancheepuram 7cm, Poonamallee 7cm and Chembarambakkam 4cm. Since Oct 1, Chennai has recorded 18cm of rainfall, about 34% above normal.