Rogue Arabian Sea storm may stop short of striking Gujarat coast

Amid reports of heavy overnight rain in southern Tamil Nadu, the Arabian Sea has expectedly thrown up a rogue low-pressure area with implications for the North-East monsoon.

The ‘low’ has started nibbling away at the moisture build over south peninsula, likely compromising the cloud build-up that sustains the North-East monsoon.

A passing Madden-Julian Oscillation (MJO) centred over tropical Indian Ocean wave in the upper air has been a benign presence for the North-East monsoon.

Periodical eastward movement of the MJO wave from West Africa to the Pacific across the Indian Ocean is a major enabler of cloud building, storm activity and rain for India, especially during the two monsoons.

An Australian Bureau of Meteorology said that the dislocated MJO is what has brought the typhoon activity over the Pacific to a halt currently.

All tracking models keep the MJO over Africa and the western Indian Ocean for the rest of the week, which will help the ‘low’ in the Arabian Sea to gather strength.

By the weekend, most models indicate the MJO will be too weak to influence tropical activity, which would hit the fortunes of the North-East monsoon as well.

The European Centre for Medium-Range Weather Forecasting suspected that the building storm may track towards the north-east Arabian Sea, and move close to Porbandar in Gujarat over next seven days.

It will careen along a trough that links it with the Maharashtra coast, as depicted in the charts. India Met Department agrees, but doubts if the system will grow beyond a depression.

Still, it will have enough nuisance value for the North-East monsoon, more or less leading to ‘shutout’ of upstream Bay of Bengal until early next week.

Normally the Bay should purr with activity during this phase of the North-East monsoon, sending rain waves towards East Coast.

But what is now on view is the prospect of a high-pressure area (sinking motion of air unlike in a low-pressure area, where it ascends) sitting over the Bay, suppressing rain activity.

Meanwhile in the North, a western disturbance is forecast to bring rain to the hills as also adjoining plains (north Rajasthan, Punjab, Haryana, Delhi, Uttar Pradesh and Bihar).