Rain deficit stays at 10% despite wet cover over Central India

Vinson Kurian Thiruvananthapuram | Updated on August 30, 2021

Negative Indian Ocean Dipole phase is believed to have impacted the monsoon

All-India rain deficit was unchanged at 10 per cent as of Sunday even after a late burst of August rainfall powered by a delayed low-pressure area began lashing parts of Central and East India as well as the West Coast. Most of August so far had delivered less than expected rain for the country as a whole.

This went against the grain of forecasts by most weather models, after August saw monsoon intermissions enforced on three occasions impacting the rain spread, watched by a negative Indian Ocean Dipole (IOD) phase. A negative IOD does not augur well for a concurrent Indian monsoon.

Fewer low-pressure areas

In the absence of credible explanations to the contrary, the negative IOD phase is believed to have impacted the monsoon. It could have cut into the upstream monsoon flows that normally head into the Bay of Bengal, in turn restricting the number of helpful low-pressure areas forming in the basin.

Meanwhile, the US National Centres for Environmental Prediction has indicated enhanced rainfall for East and Central India as also the West Coast until into the middle of September, the last monsoon month. But it is also the month when the monsoon starts retreating first from West Rajasthan.

Also read: At 58% deficit, Gujarat desperately awaits rains

On Monday morning, India Meteorological Department (IMD) said that a fresh low-pressure area emerging from the Bay of Bengal has entered inland and set up a perch over South Chhattisgarh. It is likely to move West-North-West across Central and West India during the next 3-4 days.

Helpful monsoon features

Other monsoon-friendly features include the monsoon trough that lies to South of its normal position (and hence active) and likely remaining so for the next 3-4 days. But its eastern end is likely to shift north of its normal position from September 3 and the western end thereafter, the IMD said.

As much is indicated by the US National Centres for Environmental Prediction which sees a pick-up in rainfall not just along the Himalayan foothills during the week of September 6 to 14 but also over Central India and the West Coast, likely triggered by a follow-up low-pressure area in the Bay of Bengal.

On Monday, the east-west shear zone of monsoon turbulence ran along a latitude South of Panaji to Ballari and North of Nellore, which will sustain for next two- to three days. To the South-West, the offshore trough that receives the monsoon flows first, ran down from Karnataka to Kerala coast.


Widespread rain seen

The IMD has forecast fairly widespread to widespread rainfall with isolated heavy falls over Chhattisgarh on Monday; Vidarbha from Monday to Wednesday; East Madhya Pradesh on Monday and Tuesday; and West Madhya Pradesh and East Gujarat on Tuesday.

Fairly widespread to widespread rainfall is forecast over Saurashtra and Kutch on Wednesday; Konkan and Goa from Tuesday to Thursday; and East Rajasthan, Madhya Maharashtra and Marathwada until Wednesday. Isolated very heavy falls are likely over Konkan and Goa (Mumbai included) and East Gujarat Region on Wednesday and over the rest of Gujarat on Thursday.

Rain for Northeast, South

Rainfall is likely to enhance over Northeast India and the plains of West Bengal and Sikkim from Wednesday. Fairly widespread to widespread rainfall with isolated heavy falls is likely over the South Peninsula until Tuesday. Isolated heavy to very heavy falls are likely over Telangana today.

As for Northwest India, rainfall will be scattered along both the hills and over the adjoining plains during next four days. Isolated heavy falls are forecast Uttarakhand on Monday and over Uttar Pradesh on Monday and Tuesday.

Published on August 30, 2021

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