The Hindu Business Line : Storm may survive landfall to last a while

It will have slowed down significantly on its tracks by then but not before driving up enough rain to drench parts of Orissa and even further east, according to model projections by the European Centre for Medium-Range Weather Forecasts (ECMWF).

This only goes to vouch for the potency of the Bay system that has caused some record-breaking rainfall all along its course, said Dr Akhilesh Gupta of the National Centre for Medium Range Weather Forecasting (NCMRWF).

Forecast put out by the NCMRWF spoke about the possibility of widespread rainfall with heavy to very heavy falls to continue at a few places over north Tamil Nadu, coastal Andhra Pradesh and Rayalaseema over the next 48 hours as well. Isolated heavy rainfall may also occur over the rest of Tamil Nadu, Karnataka and Telangana during the next two to three days.

Some other models show the system pumping itself up to become a severe cyclone before making landfall, stopping on its tracks for some time and re-curving its way back to the sea where it will dissipate. But, Dr Gupta ruled out the prognosis saying specific atmospheric features would not allow the system to curve back into the sea.

He also did not agree with predictions that weather disturbances over the Bay of Bengal will be comparatively toned down during November. This is because the Inter-Tropical Convergence Zone (packing some of the heavy rain belts in the tropics) now extended right from the Arabian Sea eastwards into the central Pacific.

Weather systems forming in the Pacific and South China Sea have been showing a tendency to move west-northwest during this season and this had opened up a route into India's territorial waters and into the Bay of Bengal. Any remnant of the Pacific/South China Sea systems crossing over would have some well-developed dynamics associated and reach the Bay waters to set up storms, even cyclones.

Conditions obtaining over the Bay are just right for this to happen, since the prevailing anti-cyclone has settled into the best possible slot at around 22 deg N. It has a core of easterlies to the south and aids the development of the northeasterlies of the monsoon system.

The typical `low wind shear' (change of winds with height) values associated with the northeast monsoon will act as a catalyst in the process. The shear zone is an elongated one due to the presence of a weaker counterpart system to the east over the Arabian Sea.

This `east-west shear zone' is another factor that has been instrumental in causing the widespread precipitation till now during the season.

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