India Meteorological Department (IMD) has assessed that a cyclonic circulation is likely to form over the North Andaman Sea around Monday/Tuesday and move towards the country’s East Coast (Tamil Nadu-Andhra Pradesh). It is likely that it may intensify as a low-pressure area by Thursday over the South-East Bay of Bengal, away from the Tamil Nadu coast.

There is moderate probability that it would concentrate into a depression over the West-Central Bay (off Andhra Pradesh) during the week October 20 to 26. To the opposite side, a circulation may form over East-Central and adjoining South-East Arabian Sea (off Karnataka coast) around by Tuesday and intensify into a ‘low.’ But easterly winds during the transitioning monsoon may push it farther out into the sea.

Advancing area of dryness

The progressively thinning belt of active rainfall seems to have shifted entirely towards the Andaman and Nicobar Islands and along an almost straight line to the South Peninsula as the South-West monsoon readies to withdraw from more parts of North-West India, West and East India during the next two to four days.

Almost the entire northern half of the country remained cloudless, indicating the influence of the advancing area of dry air associated with the delayed monsoon withdrawal. The IMD said on Friday the 2022 season has exited entire Uttarakhand, Uttar Pradesh and Gujarat; most parts of Madhya Pradesh and some parts of Bihar, Jharkhand, Chhattisgarh and Maharashtra. The large anticyclonic circulation (dry air and higher pressure) is establishing its presence over North-West India and adjoining Central India, which will encourage the retreating but moisture-laden seasonal easterlies from across the South China Sea and the Bay of Bengal to blow towards the South Peninsula.

North-East monsoon

The withdrawal line of the predecessor South-West monsoon and the easterly winds towards the southern flanks of the anticyclone will seamlessly merge into the moist easterlies from across the Bay, gradually precipitating the North-East monsoon (NEM, or monsoon on retreat), so named due to the origin and direction of the wind flow. Numerical models of the India Meteorological Department (IMD) continue to predict that the north-easterly wind regime may not achieve the desired level and strength until October 20.

Rains to continue over South

Fairly widespread to widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning over Tamil Nadu, Puducherry, Karaikal, Kerala and Mahe until Tuesday; over South Interior Karnataka until Monday; North Interior Karnataka until Sunday; over Telangana and Coastal Karnataka on Saturday; and over Lakshadweep on Tuesday. Isolated very heavy rainfall is also likely over Tamil Nadu, Puducherry, Karaikal, Kerala and Mahe on Monday and Tuesday. Fairly widespread to widespread light to moderate rainfall with isolated heavy falls are over the Andaman and Nicobar Islands from Saturday to Tuesday.  

Bay may stay animated

Towards father East of the Bay and beyond the line where India’s territorial jurisdiction ends, activity is building over the South China Sea and the adjoining West Pacific. This will likely rub off on the Bay and trigger the formation of helpful circulations over these ocean basins. Global models on Friday pointed to three such systems lining up one after the other over the South China Sea and towards the East of the Philippines. IMD’s numerical models suggest the Bay will remain animated into this week and next week.