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Fresh rains to break out over deficit areas of Gujarat

Vinson Kurian Thiruvananthapuram | Updated on September 18, 2021

Monsoon withdrawal gets delayed in the process

The monsoon has less than a fortnight for its four-month-long run to end but its month-long withdrawal has hit a bump over the same geography it normally gets initiated in, with India Meteorological Department (IMD) predicting fairly widespread rainfall with isolated heavy falls East Gujarat, Region, Rajasthan and western Madhya Pradesh over the next three days.

Rainfall activity over Gujarat State is likely to increase from tomorrow (Sunday) and the IMD has forecast widespread rainfall with isolated heavy to very heavy rain over Gujarat and east Rajasthan until Tuesday (September 21) despite the causative weather system having weakened.

Well-marked ‘low’ weakens

Friday’s well-marked low-pressure area over north-west Madhya Pradesh and adjoining south-west Uttar Pradesh has weakened into a conventional ‘low’ that lies over north-west Madhya Pradesh and adjoining east Rajasthan on Saturday morning. It may become less marked by Sunday.

This wet cover is supported by the presence of the monsoon trough along its canonical alignment from Jaisalmer, Ajmer, the centre of the ‘low’ north-west Madhya Pradesh and adjoining east Rajasthan, Satna, Jamshedpur, Digha and thereon south-eastwards to the east-central Bay of Bengal.

This alignment is ideal for active monsoon conditions not commonly found during the month of September which normally sees rains lifting from the north-western outpost of West Rajasthan and adjoining Gujarat early in the month. This year, on the contrary, it lies south of its normal position on Saturday and may remain as such for the next five days.

Circulation in Bay of Bengal

A secondary trough runs down in from the north-west Arabian Sea off Gujarat to the cyclonic circulation associated with the ‘low’ over north-west Madhya Pradesh and adjoining east Rajasthan across Gujarat, and is capable of sustaining a rainfall regime under its footprint.

Meanwhile, to the east, another rain-driving cyclonic circulation (not amounting to a ‘low’) will persist on Saturday over the east-central and adjoining north-east Bay of Bengal. It is likely to move towards north Odisha-West Bengal coasts into the night to preside over a fresh rain spell.

The IMD has said that rainfall may increase over Odisha and the plains of West Bengal with fairly widespread to widespread isolated heavy isolated rain fall for three days from today (Saturday).

Rain for parts of North-West

An extended IMD outlook for the next week (September 23-25) predicts fairly widespread to widespread rainfall with isolated heavy to very heavy falls over Gujarat. Fairly widespread to widespread is also likely over most parts of the country except Jammu, Kashmir, Ladakh, Himachal Pradesh, Punjab, Haryana and West Rajasthan where isolated to scattered rainfall is likely.

In the meantime, fairly widespread rainfall with isolated heavy falls is likely over east Gujarat, Rajasthan and west Madhya Pradesh until tomorrow (Sunday) before it intensifies over all of Gujarat. Widespread rainfall with isolated heavy to very heavy falls is also likely over Gujarat and east Rajasthan until Tuesday.

Fairly widespread rainfall with isolated heavy falls is likely over Uttarakhand and Himachal Pradesh during this period while light to moderate isolated/scattered rainfall is expected over the rest of north-west India until midweek next week, ruling out initiation of monsoon withdrawal.

US agency concurs with outlook

The US Climate Prediction Centre has forecast above-average rainfall for Gujarat, Saurashtra, Kutch, North Konkan, West Madhya Pradesh, South-West and adjoining South-East Rajasthan and adjoining South-West Madhya Pradesh during the ongoing week (September 15-21).

The US agency goes on to indicate almost the same trend for these regions (except possibly south-west Uttar Pradesh) with a weekly total rainfall in the ‘upper third of the historical range.’ As on Saturday, the monsoon trough extended from India into South China Sea/West Pacific.

MJO stalls over Indian Ocean

The CPC also indicated that a helpful Madden-Julian Oscillation (MJO) wave has stalled over the East Indian Ocean (southern parts of the Bay of Bengal) favouring enhanced convection, clouds and precipitation. It is forecast to move ever so slowly into the Maritime Continent (Indonesia et al).

This is expected to keep the South China Sea/West Pacific storm season busy with the area around the Philippines remaining moderately favourable for tropical cyclogenesis (typhoon formation). This augurs well for the Indian monsoon so long as the backbone trough back home over land stays active.

Published on September 18, 2021

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