Northeast monsoon likely to reach Tamil Nadu around October 17, RMC says

The Northeast monsoon is expected to set in over Tamil Nadu around October 17 or 18, bringing much-needed rainfall to a state managing water deficits after months of transition.

According to the Regional Meteorological Centre in Chennai, the arrival depends on the full withdrawal of the southwest monsoon from peninsular India by October 15, which will clear the way for seasonal winds to shift into northeasterlies.

What the weather models show

Meteorologists are watching two successive developments over the eastern seas. An upper air cyclonic circulation is due to form over the Andaman Sea around October 11, which should then seed a low-pressure area across the southeast Bay of Bengal by October 13.

V.R. Durai, who heads the Regional Weather Forecasting Centre at the RMC, said forecasters are tracking the path and strength of that circulation closely. If the system tracks towards the mainland or edges closer to the Tamil Nadu coastline, it will speed up the wind reversal needed to declare the monsoon's arrival. Current numerical models suggest the system will not intensify beyond a low-pressure area, but its presence should be enough to pull moist easterly winds across the coast.

Heat before the rain

Until the monsoon takes hold, daytime conditions across several districts remain harsh. A transitional weather phase has kept skies clear enough to drive up mercury levels, particularly across north interior Tamil Nadu, where above-normal temperatures are expected to persist until October 14.

Over the weekend, Erode and Madurai airport shared the state's highest maximum temperature at 37 degrees Celsius. Several other monitoring stations logged readings roughly two degrees above their seasonal averages.

A separate atmospheric feature over the Gulf of Mannar and neighbouring south Tamil Nadu continues to generate sporadic relief. Light to moderate showers are forecast to hit southern and interior districts through October 16. Even with that moisture around, forecasters noted that the lack of continuous cloud cover means localized heat will linger until widespread rainfall establishes itself.

What happens next

The RMC projects a steady dip in day temperatures across Tamil Nadu starting October 16, as cloud cover thickens and easterly air currents push deeper inland. Once winds establish a firm northeasterly pattern following the southwest monsoon's October 15 exit date, regular seasonal rain should commence across coastal and interior belts.