The India Met Department (IMD) on Wednesday formally put out a watch for a potential cyclone developing in the Arabian Sea, after it advanced by a day the formation of a low-pressure area in the basin.

According to the IMD’s evening bulletin, the ‘low’ would form by Friday, concentrate into a depression by Sunday, before going on to become a tropical cyclone away from India’s West Coast.

Bay, too, under watch

Global models have been pointing to the possibility already, which they have now extended into the Bay of Bengal as well, after a persisting circulation off the Tamil Nadu-Sri Lanka coast started engaging their focussed attention.

Some of these models indicated that this circulation could take advantage of the westerly flows that it would share with the Arabian Sea system and intensify into a storm in the Bay.

They see this system, in combination with a westerly trough (western disturbance) traversing the North Arabian Sea around the same time, likely altering the track for onward movement of the prospective Arabian Sea cyclone.

The IMD has initially projected a north-westward track that should take it away from the West Coast and the Lakshadweep Islands. The altered course could re-orient it towards the Karachi-Gujarat coasts and adjoining South-West Rajasthan.

Westerly trough

The IMD’s extended outlook also portends to the movement of a westerly trough with a limb extending into the North Arabian Sea that could hold the cyclone on its tracks. This ‘limb’ could scoop up the cyclone from over the mid-Arabian Sea and put it in line with the movement of its parent — the westerly trough — and force it recurve.

The US National Weather Services agency, which was among the first to pick the north-west track towards Oman, now sees the system being propelled towards the Karachi-West Gujarat coasts.

The US Navy Global Environmental model and the UK Met model too agree with the outlook that the prospective cyclone may not go the distance to touch base over the Oman coast.

Heavy rain outlook

Meanwhile, the IMD has warned fishermen not to venture into the South-East and Central Arabian Sea from Saturday (October 6) onwards. Those in the deep-sea areas have been advised to return to coast before Saturday.

It has also said that a low-pressure area is likely to form over the South-West Bay around Monday (October 8) but has not indicated the possibility of strengthening or the track of movement. Global models say the Chennai-South Andhra Pradesh coast may be hit.

Tamil Nadu and Kerala may witness fairly widespread rain/thundershowers with heavy/very heavy rains during next five days in the run-up to formation of the Arabian Sea ‘low’ and its intensification.

The Ghat areas of Tamil Nadu and adjoining parts of Kerala are likely to experience isolated extremely heavy falls around Sunday. Isolated to scattered thundershowers are also likely over parts of Maharashtra on Thursday and Friday.

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