Heavy rainfall likely over delta, coastal belts for four days, signalling return of monsoon’s active phase

The prevailing weather system over the Bay of Bengal is expected to bring intense downpour over the delta and coastal districts between November 16 and November 19, signalling the return of Northeast monsoon’s active phase after a lull.

The system caused sporadic, sudden showers over parts of north coastal areas, including Chennai, on Thursday. The Regional Meteorological Centre has forecast an increase in rainfall over the State from Sunday onwards, which may be heavy in four delta districts, including Thanjavur and Mayiladuthurai, and the Karaikal area on Sunday.

Intense rainfall would cover 11 delta and coastal districts, including Tiruvarur, Villupuram, Nagapattinam, Cuddalore, and Puducherry and Karaikal area on November 17. Chennai and its surrounding districts too may receive heavy rainfall on Monday. It will then be the turn of extreme south coastal TN- Thoothukudi, Tirunelveli and Kanniyakumari districts- to get heavy showers on November 18.

Rainfall is expected to spread to many places in the State on November 19, with isolated heavy showers in four districts, including Tiruvarur. Officials of the RMC noted that an upper air cyclonic circulation persisting over southwest and adjoining Southeast Bay of Bengal, which is expected to move westwards, will cause wet weather.

The dry weather and rainfall confined to a few areas this month have brought the State’s seasonal rainfall to 25.3 cm, slightly below the average of 26.6 cm since October 1. However, officials pointed out that the NE monsoon sometimes is punctuated by long dry spells and any shortfall could be offset by a rainspell lasting a few days.

B.Amudha, Head, (Additional in-charge), RMC, said the system, which may persist for a few more days, is likely to bring rainfall across TN. It is expected to revive the active monsoon phase.

It was the same system that brought sporadic, sharp showers in a few places close to coast, including Chennai, on Thursday morning. “When moisture is dragged towards the weather system, wind stability may occur and trigger isolated rainfall like the one on Thursday morning,” she said. Various other local factors could also contribute to such sporadic rainfall events, which can be predicted only through nowcast.

Oothu in Tirunelveli received the heaviest rainfall of 9 cm during the 24 hours ending 8.30 a.m. on Thursday. Light to moderate rainfall continued in various places, including Pamban in Ramanathapuram district (5 cm), Pallikaranai (2 cm), Taramani and Meenambakkam in Chennai and Thoothukudi and Villupuram districts till 6 p.m. on Thursday.

The RMC has forecast some areas in Chennai may get light rainfall on Friday.