Monsoon begins to exit Rajasthan, signals churn in Bay

A seasonal anticyclone marked by higher pressure and dryness has developed over the western parts of North-West India causing substantial reduction in moisture content and rainfall, and signalling the start  of the withdrawal of the monsoon.

India Meteorological Department (IMD) said on Wednesday that the South-West monsoon has exited from parts of West Rajasthan and parts of  Gujarat with a delay of almost 20 days in a trend that has become a new normal in recent years.

Exit to gather pace

The withdrawal line passed through Bikaner, Jodhpur, Jalore and Bhuj on Wednesday. The IMD assessed that conditions are becoming favourable  during the next 3-4 days. In the past five years, the earliest date of withdrawal from West Rajasthan was  September 15, in 2016, followed by September 27 in 2017; September 28 in 2020; September 29 in 2018; and the elaborate process was delayed most in 2019 when it got into motion as late as on October 9.

Bay of Bengal in a churn

As South-West monsoon began its long withdrawal march from the North-West, the Bay of Bengal is shaping up to the monsoon in reverse (North-East monsoon) as the anticyclone entrenches and associated north-easterly to easterly winds sweep East India, the Bay and Peninsular India, in that order.

Hastening the process is a likely low-pressure area building over the North Andaman Sea in the next four days (by October 10) with a phalanx of easterly to north-easterly winds which will strengthen as the anticyclone weighs in over the northern half of the country with associated easterly winds.

IMD expects the low-pressure area to become ‘more marked’  and move along a typical West-North-West track towards the rain-weary South Odisha and North Coastal Andhra Pradesh coast during the subsequent 4-5 days (mid-October).

The US Climate Prediction Centre has pointed to the ‘imminent’ possibility of a tropical storm  cyclone across upstream South China Sea during October 6 to 12 which may track slowly, flooding Hainan Island and/or parts of Vietnam.

Another storm may form just East of the Philippines which models take for a trek further upstream across the West Pacific  between October 13 and 19. Enhanced cloud-building, model guidance and climatology favour an increased chance of a storm development over the Bay by mid-October.

The axis of heaviest rainfall is expected to shift north across South, South-East Asia along with  West Pacific in next two weeks, the US agency said, with India likely being a beneficiary.

Resident circulation over TN

Back home, the IMD has already been tracking a potent cyclonic circulation over the Tamil Nadu coast, complete with a trough in easterlies originating from it to the North Konkan across central parts of Tamil Nadu, North Kerala and Coastal Karnataka instigating a persisting and sustained wet spell. Isolated heavy rainfall will continue over Kerala and coastal Karnataka until October 10; over Tamil Nadu on Thursday, over interior Karnataka until Friday.

Isolated very heavy falls were forecast over south Interior Karnataka, Tamil Nadu, and Kerala on Wednesday.

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