Chennai could receive moderate to heavy rain from Sunday night into Monday morning as a developing cyclone over the Bay of Bengal interacts with a low-pressure area over the Arabian Sea, while the India Meteorological Department has issued rainfall alerts across Tamil Nadu.
The forecast places Chennai, Chengalpet, Kancheepuram and Tiruvallur under a yellow alert for Monday, indicating heavy rain of 6-12 cm in 24 hours. The IMD has issued a red alert for three districts along the Western Ghats on Sunday, warning of heavy to very heavy rainfall between 12 cm and 20 cm in 24 hours. Fourteen districts are under an orange alert for heavy to very heavy rain.
V R Durai, director of the Area Cyclone Warning Centre at the Regional Meteorological Centre in Chennai, said the system over the east-central Bay of Bengal could draw the Arabian Sea low-pressure area towards it. This interaction may intensify rainfall over Chennai and neighbouring districts on Sunday, according to the report.
A trough extending from the cyclonic circulation linked to the Arabian Sea system towards north coastal Tamil Nadu could further enhance rainfall. The trough is expected to continue bringing rain until October 26 before gradually weakening, Durai said. After that, dry weather may prevail over Chennai for a few days.
On Sunday, Chennai and its suburbs may receive moderate to heavy rain accompanied by thunderstorms and lightning in some areas. Partly cloudy conditions are expected, with maximum temperatures of 31-32°C and minimum temperatures of 25-26°C. The forecast could affect road travel and routine urban movement during the Sunday night and Monday morning period, particularly in areas experiencing intense short-duration spells.
The weather system is expected to move towards the south Andhra Pradesh-north Odisha coast before turning northwards towards Gangetic West Bengal, with landfall expected during that progression. From October 27 to around November 3, moisture is likely to remain concentrated around the cyclone, allowing drier conditions over Chennai and a slight rise in daytime temperatures.
Durai said temperatures were unlikely to become excessively high because the Sun had moved south of the equator. Blogger Pradeep John also said the heavier spells could occur from Sunday night to Monday morning, followed by a break in rainfall.
Chennai has already recorded 278.8 mm of rain since October 1, around 69% above normal, according to the report. Kancheepuram has received 163.8 mm, around 28% above normal, while Chengalpet has recorded 145.2 mm, around 4% below normal. Tiruvallur has received 198.9 mm, around 48% above normal. The current alert period will run through October 26, after which the forecast indicates a likely temporary break in rain over Chennai.
