Large-scale thunderstorms and rough weather have been warned for many parts of the country during the weekend.

This results from the expected arrival of a huge and massive western disturbance with a reach into even South Peninsula.

MASSIVE SIZE

The size and scale are unprecedented, say weather watchers, and comes close on heels of a major predecessor disturbance.

The latter had set off heavy rain and snowfall in the hills thunderstorms and hailstorm in North-West India last week.

But this time round, hailstorm can break out even in peninsular India, particularly to the east.

Eastern parts of Maharashtra and Andhra Pradesh could bear the brunt since the causative core embedded in the disturbance is expected to sit smack over South Rajasthan/Gujarat.

This is much south to the normal position, and, hence, the weather implications for the entire peninsula.

Additionally, the long limbs of the western disturbance will cause an away-going easterly wave across the Bay of Bengal to amplify.

This would cause massive moisture incursion into the atmosphere, which would be dumped as rain over the eastern peninsula.

The US agency forecasts said rainfall up to 600 per cent above normal for the year could be expected in the region.

The India Meteorological Department (IMD) said that rain/snow would whiten Western Himalayas with heavy falls from Friday.

Rain or thundershowers would lash Central, East and adjoining Peninsular India on Saturday and Sunday.

CROP ALERT

Hailstorm may break out over the plains of North-West and Central India and even adjoining the peninsular India.

Farmers have been advised to withhold irrigation, apply fertiliser after Sunday and store the harvest produce securely from Thursday.

Rain or thundershowers has been forecast at a few places over extreme south peninsular India.

The IMD said that last week’s western disturbance had affected mainly western Himalayan region and plains of North-West India.

The amplitude of the western disturbance and associated trough would deepen to 15 deg latitude (caressing Maharashtra and Andhra Pradesh around the middle).

What triggers the rough weather is intense mixing of two different air masses (tropical and extra-tropical) over Central India. There would be incursion of moisture from Arabian Sea but very high moist air incursion would take place from Bay of Bengal.

This situation and accentuated convection is very conducive for development of high ‘atmospheric instability.’

vinson.kurian@thehindu.co.in

(This article was published on February 12, 2013)
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