Heavy rainfall likely in S. Peninsula
Thiruvananthapuram, Oct. 12
The outlook on the arrival of northeast monsoon has been largely maintained, with the crucial `shear zone' of atmospheric turbulence becoming better organised over the peninsula.
Both the National Centre for Medium range Weather Forecasting (NCMRWF) and India Meteorological Department (IMD) are in agreement that the ongoing rainfall activity over extreme south peninsular India is likely to increase during the next two to three days.
Mr J.V. Singh of the NCMRWF sought to confirm this, saying that the `retreating monsoon' is expected to break in during this period. The shear zone is oriented along an east-northeast to west-southwest alignment from the Bay of Bengal to the Arabian Sea. But given the high vertical wind shear, it's unlikely that a tropical cyclone will develop in the Bay at least over the next five days.
Wind shear is the abrupt rate of change of wind velocity (direction and/or speed) per unit of distance and is normally expressed as vertical or horizontal wind shear.
The Bay has been known to erupt into northeast monsoon mode with a signature cyclone during this time of the year. But high wind shear blows away the top of a cyclone in formation.
The prevailing strong westerly winds may also have stopped the westward movement of the persisting `low', and guided it into northeast Bay. Model predictions suggest that this is likely to step up rainfall activity over West Bengal and the North-eastern States during next 24-48 hours. Predictions support a scenario where an easterly pulse from the South China Sea drifts into the Bay to prospectively grow into a low. This is expected to happen by mid-week next week.
The rain-driving offshore trough from South Konkan to Kerala coast persists. Fairly widespread rainfall is likely over Konkan, Goa, Coastal Karnataka and Kerala during next 24 hours.
Forecasts suggest that rain/thundershowers are likely at many places over Andaman and Nicobar Islands, Coastal Karnataka, Lakshadweep and Kerala; and at a few places over south interior Karnataka, coastal Andhra Pradesh, Tamil Nadu and Puducherry.