The India Meteorological Department (IMD) has upgraded the outlook for a pre-monsoon depression over the South-West Bay of Bengal to that of a tropical cyclone, which it expects to materialise by Saturday.

A preparatory low-pressure area is expected to take shape by Thursday, before undergoing gradual strengthening into a powerful cyclone likely headed for Tamil Nadu, past East Sri Lanka, over the next three to four days.

Rough seas warned

The IMD has warned that this could result in ‘very rough’/‘high sea’ conditions over the South Bay and squally/gale force winds with speeds reaching up to 80 km/hr along and off the Tamil Nadu coast and the Comorin area from Sunday to Tuesday.

It has forecast widespread rainfall with isolated very heavy to extremely heavy rain for Tamil Nadu and adjoining Andhra Pradesh. This would suggest a landfall of the cyclone just to the South of Chennai, as some models are forecasting.

Fairly widespread rainfall with isolated heavy falls and squally winds are also likely over Kerala and Coastal Karnatakaon the three days, the IMD said. However, there are some models that do not agree with the north-west track of the cyclone towards Sri Lanka-Tamil Nadu. Instead, they chart a diagonal path for it across the open Bay towards Bangladesh/Myanmar.

This should worry Tamil Nadu since rains from the cyclone, which would otherwise fill its reservoirs, would be wasted out at sea, even while appreciating the devastating impact it has on life and property.

The IMD said that the Bay is prone to cyclonic development during the pre-monsoon months of April and May.

Cyclone patterns

Usually, cyclones form in the South and adjoining Central Bay and move initially north-west, north, and then recurve to the north-east.

This track takes them towards the Arakan (Myanmar) coasts in April. But in May, they could head towards India’s East Coast — Andhra Pradesh-Odisha-West Bengal — or the adjoining Bangladesh coast.

On the other hand, cyclones do not form in the Arabian Sea during January, February and March, and they are rare in April, July, August and September.

They generally form in the South-East Arabian Sea and adjoining Central Arabian Sea in May, October, November and December, and in the East-Central Arabian Sea in June.

Some of them originate in the Bay, travel across the peninsula, weaken, and emerge into Arabian Sea as low-pressure areas where they may re-intensify as fresh cyclonic storms.

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