Precipitation is triggered by an offshore trough

Districts along the Western Ghats will continue receiving heavy to very heavy rainfall till Saturday. One or two areas may record extremely heavy rainfall in these districts. Avalanche recorded nearly 82 cm — the highest volume of rainfall recorded in the State’s history during the past 24 hours, according to the Meteorological Department.

The offshore trough, which is bringing rainfall to States such as Kerala and Karnataka, is influencing orographic rainfall in districts along the Western Ghats, noted Met officials.

During the past 24 hours, ending 8.30 a.m. on Thursday, many weather stations in Nilgiris, Coimbatore and Theni districts experienced very heavy rainfall. Following Avalanche, Upper Bhavani received 30 cm.

Devala in Nilgiris district and Valparai in Coimbatore district also registered 21 cm and 20 cm of rain respectively. Officials said orographic rainfall occurred in the mountain regions during monsoon.

N. Puviarasan, director, Area Cyclone Warning Centre, Chennai, said the region along the Western Ghats would continue to receive such orographic rainfall and the phenomenon would bring localised rainfall.

While a few places in the interior and southern parts of the State would receive light to moderate rainfall till Saturday, heavy rainfall would continue in Nilgiris, Coimbatore and Theni districts. One or two places may record extremely heavy rains above 21 cm.

“The taluk office in Avalanche measured rainfall through a manual rain gauge. So a team of officials will travel there next week to verify details,” he said.

“We expect rainfall to come down in the Western Ghats districts, as the monsoon trough will move to the foothills of Himalayas in a few days. Convective rainfall over other parts of the State, including coastal districts, will begin in four or five days,” he added.

The Meteorological Department has forecast light rains over Chennai in some areas till Saturday. Fishermen have been warned not to venture into sea off the Tamil Nadu and Puducherry coasts on Friday due to strong westerly winds.