CHENNAI: A rare spell of 10cm rainfall in parts of Chennai in March has taken everyone by surprise. Strong gusts with thunderstorms have swept through the city and few other districts under heavy convective weather, with late evening and night showers likely to continue over the next couple of days, especially in southern Tamil Nadu, according to the Regional Meteorological Centre (RMC).
Rainfall occurred at many places across Tamil Nadu, Puducherry and Karaikal, with several areas recording moderate to heavy spells. Chennai, Pallikaranai and Varattupallam in Erode district recorded the highest rainfall of 10cm each, followed by Medavakkam and Ammapettai (9cm each), while Okkiyam Thoraipakkam, Sankaridurg and Arcot received 8cm each. Several other locations across Cuddalore, Salem, Kallakurichi, Dindigul and Chennai recorded between 4cm and 7cm of rainfall, indicating widespread convective activity across regions.
Meteorologists said the pattern of rainfall is likely to persist, particularly during late evenings to night. V R Durai, head of the Area Cyclone Warning Centre, said the state is entering a phase of increased convective activity. “Convective rainfall will start in March. Tamil Nadu, Andhra Pradesh and Karnataka have reported widespread rains in the last two to three days,” he said.
He attributed the current weather to synoptic systems over the surrounding seas. “The Bay of Bengal and Arabian Sea have anti-cyclonic systems due to which wind is being pushed, leading to more moisture incursion. There is also a trough supporting this activity,” Durai explained. He added that wind discontinuity will be more pronounced in April and May when heating increases.
Sivananda Damodara Pai, head of the RMC, pointed to wind interactions as a key trigger. “There is some kind of wind discontinuity in the southern parts. This has triggered local convective activity,” he said. “When easterly winds move from the Bay of Bengal towards the Arabian Sea, rainfall activity can occur over the southern parts.”
He added that rising temperatures are enhancing moisture availability. “Temperatures are increasing, which will increase the moisture. We had clear skies for a few days, and a temperature dip due to the trough has caused wind discontinuity,” Pai said.
Rainfall is likely to gradually reduce after March 21, with light showers confined to isolated areas, mainly along the Western Ghats and southern districts through March 25.