Chennai, Oct 19:
An intense spell of rainfall lashed Chennai on Saturday evening, with several parts of North Chennai receiving more than 6 cm of rain within an hour. The sudden downpour, which inundated roads and disrupted traffic, was linked to an active weather system over north Tamil Nadu and adjoining coastal Andhra Pradesh as the northeast monsoon gathered strength.
According to the Regional Meteorological Centre, an upper-air cyclonic circulation over north Tamil Nadu and coastal Andhra Pradesh, along with a trough extending from Lakshadweep to the southwest Bay of Bengal, contributed to the rainfall. Such systems can draw moisture-laden air into the region and create conditions favourable for the rapid development of rain-bearing clouds. When these clouds produce intense convection over a limited area, rainfall can be exceptionally heavy within a short period.
The concentration of rain over North Chennai made the spell particularly severe. Tondiarpet recorded 7.3 cm between 6 pm and 7 pm, while Coronation Nagar received 7 cm and Thiruvottiyur 6.9 cm during the same hour. Private weather forecaster Pradeep John described the spell as cloudburst-like, with around 10 cm of rain reported in parts of North Chennai within an hour. Such a description indicates the intensity of the downpour and does not, by itself, mean that an officially confirmed cloudburst occurred.
The timing and intensity of the rainfall also exposed the difficulty of managing sudden water inflows in a densely built-up city. When large volumes of rain fall in a short time, stormwater drains and local channels may struggle to carry the water away quickly, particularly in low-lying areas and stretches where drainage is restricted. This can lead to temporary waterlogging, traffic congestion and difficulties for pedestrians and motorists.
The Regional Meteorological Centre said the northeast monsoon had entered an active phase, with rain expected across Chennai and several other districts. A yellow alert was issued for 17 districts, including Chennai, Tiruvallur, Chengalpattu, Kancheepuram and Cuddalore, warning of heavy rainfall. The episode underlined the need for timely weather alerts, effective drainage maintenance and rapid civic response as intense, localised rain spells become a major challenge during the monsoon.
The meteorological explanation and reported rainfall figures are based on reports published after Saturday’s downpour.