The India Met Department (IMD) has formally notified the possibility of a low-pressure area forming over West-Central and adjoining North-West Bay of Bengal in the next four to five days.

A US National Weather Services forecast had last week alluded to this event being precipitated in continuum with the approach of destructive West Pacific super typhoon Mangkhut towards the Philippines, Hong Kong and South-East China.

Trough to shift

As if on cue, the eastern end of the monsoon trough across the plains of North India that lies currently nestling along the Himalayan foothills, would slide down South and dip into the Bay.

The trough opens itself up to any system developing in the Bay to receive the monsoon easterlies and drive in accompanying rains into the hinterlands of East and Central India.

In the prolonged absence of systems in the Bay, the trough migrates to the North, as it did last week when the monsoon went into a weak phase except over the North-East and along the foothills. The IMD said that the trough continues to run close to foothills and may stay as such during the next two days. But the eastern end may shift southwards from Saturday.

May intensify?

Meanwhile, the US model forecasts said that the ‘low’ in the Bay could intensify into depression strength and cross the Odisha and North Andhra Pradesh coast after September 20.

It would take shape over the East-Central Bay adjoining the Myanmar region and travel west-north-west towards the coast. The IMD more or less agreed, but indicated that the ‘low’ would be driven South over land towards Central India.

This movement would be overseen by the opposing northerly flows from an advancing anticyclone from Rajasthan, signalling the delayed withdrawal of the South-West monsoon from the region.

Elsewhere, the North-Eastern States and the hills of Bengal may witness widespread to widespread rainfall with isolated heavy falls until tomorrow due to due to downstream convergence of westerly winds with the southerlies from the Bay. Subdued rainfall may prevail over the rest of the country during the next three days. But the Western Himalayan region and Punjab are likely to witness enhanced precipitation with the arrival of a western disturbance.

Western disturbance

Arrival of the disturbance is another signal of the weakening of the monsoon, with winds likely turning gradually anti-cyclonic (which consolidats dry weather) over the Rajasthan region into next week.

The IMD said that winds over the Andaman Sea, East-Central Bay and South-West Bay would strengthen from Sunday ahead of formation of the ‘low’ on Tuesday.

In view of the likely adverse sea conditions, fishermen are advised not to venture into these areas on Sunday and Monday. They may plan their trips into the deep seas based on further updates only.

An extended outlook valid from September 19 to 21 said that widespread rain is likely over Andaman and Nicobar Islands while being scattered to fairly widespread over the northern parts of Peninsular India and adjoining Central India.

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