A weakening and away-going depression from the Bay of Bengal along the Myanmar-Bangladesh side is unlikely to have any significant direct impact on mainland India. But the atmospheric transition accompanying monsoon withdrawal is expected to keep the South Peninsula wet through the rest of the week.
The European Centre for Medium-Range Weather Forecasts (ECMWF) indicates a spread of rain and seasonal thunderstorms across the peninsula as the south-west monsoon is set to give way to its north-east counterpart. India Meteorological Department (IMD) outlook broadly concurs, forecasting rainfall ranging from isolated and scattered spells to fairly widespread and widespread activity across different parts of the region.
Rain, thunderstorms
Almost on cue, an upper-air cyclonic circulation has parked itself over north coastal Tamil Nadu this (Wednesday) morning. A north-south trough extended from South Interior Karnataka across Tamil Nadu to the Gulf of Mannar. The circulation and trough are expected to provide the focus for rain and thunderstorms over the peninsula during the remainder of the week, even as their position and orientation change.
Kerala and Mahe are likely to receive fairly widespread to widespread rainfall for six days from tomorrow (Thursday), while coastal Karnataka is expected to see similar activity on Thursday and Friday. South Interior Karnataka is likely to remain under fairly widespread to widespread rain today and on Thursday.
Wider rain spread
The rain footprint will be broader but more intermittent elsewhere. Isolated to scattered rainfall is likely over Coastal Andhra Pradesh and Yanam; Lakshadweep; North Interior Karnataka; Rayalaseema; and Tamil Nadu, Puducherry and Karaikal during the next seven days. Coastal Karnataka could see such activity today and again for four days from Saturday, while South Interior Karnataka is likely to receive isolated to scattered rain for four days from Friday. Telangana could also see such spells on Friday and Saturday.
Change of regime
The transition will also carry a familiar signature of the changing monsoon regime: thunderstorms, lightning and gusty winds. These are likely over Tamil Nadu, Puducherry and Karaikal for three days from today, and over Kerala and Mahe for three days from Thursday. Elsewhere, the weather map remains active without any immediate indication of a fresh system capable of delaying monsoon withdrawal. A western disturbance was present as a cyclonic circulation over north Haryana, with an associated trough aloft, while another cyclonic circulation persisted over south-east Uttar Pradesh and adjoining Bihar.
The South-West monsoon’s withdrawal has been held up for several days for now, with the retreat line remaining virtually anchored along Gurdaspur; Chandigarh; Muzaffarnagar; Aligarh; Dholpur; Udaipur, Deesa; and Naliya. A succession of depressions moving in from the Bay had kept the atmosphere unusually wet along and ahead of the withdrawal corridor, delaying the monsoon’s final retreat.
Last monsoon day
With the first depression having dissipated and the second losing its organisation after drifting eastward, the withdrawal process could gather pace from today, the official final day of the four-month South-West monsoon season. The retreat is expected to advance across East and North-East India and Central India, setting the stage for the seasonal transition to the North-East monsoon over the South Peninsula from around mid-October.
The IMD said the latest depression over the Bay had weakened into a well-marked low-pressure area over North Myanmar and adjoining south-east Bangladesh; Mizoram; and the north-east Bay. The system is expected to move towards Mizoram; Tripura; and adjoining south-east Bangladesh before weakening further into a conventional low-pressure area by Thursday, before it weakens further and becomes unimportant.
Published on September 30, 2026
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