The Hindu Business Line : Flooded tracts may fuel rain from new bay system

Floodwaters in the monsoon-affected States in the peninsula, if not draining out in time, are seen fuelling the next round of a wet spell from a brewing `low' in the Bay of Bengal basin.

Vast tracts of submerged land and plentiful supply of moisture will combine to provide the required `frictional convergence' at the ground level, which will help pump up moisture to higher levels to precipitate rain.

Ocean effect

Submerged land would be able to provide frictional convergence in much the same manner as, if not better than, the warm ocean waters, said Dr Akhilesh Gupta of the Department of Science and Technology.

Floodwater must cover more or less the same area — around 500 km in square — as the causative weather system for frictional convergence to peak. Timeframe for floodwaters to drain out from affected areas becomes crucial in this context.

Lack of required moisture feed can, however, prove counter-productive and weaken the system, Dr Gupta added.

Shifts South

The fresh Bay system is forecast to take shape by Friday. Preparatory to this, the westerly monsoon jet has shifted south to lie over South Konkan and adjoining Coastal Karnataka. Starting Tuesday, rainfall will become concentrated over South Coastal Andhra Pradesh, Rayalaseema and even North Coastal Tamil Nadu up till the time when the activity shifts to the Bay.

Conditions are favourable for the brewing `low' to intensify into a depression or even a deep depression but not necessarily a named cyclone, Dr Gupta said. The redirected westerly jet will help strengthen the flows, generating enough `spin' from lateral shear. The seasonal trough is dipping into Head Bay providing required vorticity for the system to prosper.

May retain intensity

After crossing land, the system is seen traversing much the same route as the predecessor to dump heavy rain west-northwest from Orissa, North Coastal Andhra Pradesh, interior Chhattisgarh, Telengana, West Madhya Pradesh, Vidarbha and the rest of Maharashtra.

What is significant is that the system will retain its intensity for quite some time even after crossing land. Dr Gupta also saw the possibility of a mid tropospheric cyclone organising itself over the Gujarat coast, which can further drive up rainfall over North Konkan, Goa and South Gujarat.

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