Low pressure system in Bay sets off pre-monsoon buzz

The India Met Department (IMD) has forecast the possibility of a low-pressure area forming over South-East and adjoining East-Central Bay of Bengal by Friday.

This could set off a pre-monsoon buzz in the Bay in the run-up to the onset of the South-West monsoon over the next 45 days.

Early model forecasts indicated that the ‘low’ would pick up strength, but travel away from the East coast of India (Tamil Nadu-Andhra Pradesh-Odisha) and guide itself east-north-east, eyeing the Myanmar/Bangladesh coast by April 20.

More recent forecasts (including that of the IMD) have it that the system, a depression or even a cyclone, could instead gravitate to the Bengal coast for a landfall.

These are early assessments of the likely behaviour of the system, the orientation of which would also depend a lot on concurrent western disturbances that move across North-West and East India. At least two models — from the Japanese Meteorological Agency and the UK Met Office — do not see a powerful system being initiated in the Bay any time soon.

But others do, among them the European Centre for Medium-Range Forecasts, the Navy Global Environment Model (Navgem) of the US, the Global Forecast System (GFS) of the US National Centres for Environmental Prediction, and the Canadian Meteorological Centre (CMC).

The European Centre sees the ‘low’ in South-Central Bay spinning away east-north-east to become a probable cyclone and heading towards Myanmar/Bangladesh coast.

The Navgem depicts a scenario where the ‘low’ intensifies into a powerful cyclone, barrelling its way east-north-east across the Bay towards the Bengal coast in India.

Between the GFS and the CMC, the former predicts that the ‘low’ could become a depression by April 18, by when it would have reached Central Bay, while the latter locates a full-fledged cyclone hovering in the area around the same time.

Usually in April and May, the odd cyclones form in the South and adjoining Central Bay and move initially north-west and north. They later re-curve to the North-East striking the Arakan coasts (Myanmar) in April and the Andhra-Odisha-West Bengal-Bangladesh coasts in May.

The observed pattern is that cyclones do not form in the Arabian Sea during the months of January, February and March, and are rare in April.

Most formations in the Arabian Sea move in a west-north-westerly direction towards the Arabian Gulf coast in May and in a northerly direction towards the Gujarat coast in June.

It is also to be noted that pre-and post-monsoon storms are more violent than the storms of the monsoon season.