Date:22/05/2007 URL: http://www.thehindubusinessline.com/2007/05/22/stories/2007052204341200.htm

Back Brewing thunderstorms to douse heat in South

Vinson Kurian

IMD forecasts increase in rainfall activity in west coast

Thiruvananthapuram May 21 A big-amplitude western disturbance currently affecting the country is seen as being deep enough to impart some positive vorticity (circulatory motion helping precipitation) along the west coast while triggering thundershowers to douse the heat along Andhra-Tamil Nadu coasts.

The determinedly slow and eastward-moving system will take at least two days to cover an entire swath of geography extending from Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Punjab, Haryana, Rajasthan, Delhi, Chandigarh, Uttar Pradesh, Bihar, Jharkhand, Orissa and West Bengal to Sikkim.

Convective bands along the southern fringes of the massive system are seen toying with the Goan latitude to stimulate some activity along that part of the west coast. This is also expected to lift the sagging monsoon current and create some unsettled weather resulting in rainfall.

But it is a moot question whether this would help steer the monsoon flows and sustain them, sources said.

DUST STORMS

Scattered rain/thundershower activity from the western disturbance is already impacting the western Himalayan region. Isolated to scattered dust storms/thundershowers accompanied by squalls will be widely felt across the plains of northwest India during the next two to three days.

Meanwhile, the monsoon current has advanced into more parts of southeast Bay of Bengal, parts of east-central Bay of Bengal and the entire Andaman Sea. Clusters of clouds have formed over the northwest Bay, which too are expected to set off thundershowers along the southeast coast, currently under the grip of a severe heat wave.

India Meteorological Department has predicted an increase in rainfall activity along the west coast two days from now. This will be largely the result of a string of thundershowers marching down the peninsular coast prior to the actual onset of the monsoon.

The latent heat from condensation will help warm up the atmosphere and raise its moisture-carrying capacity. This will cause the westerly flows to get further established.

Arabian Sea calm

The Arabian Sea is otherwise calm, with a cluster of clouds meandering from west to the centre remaining virtually stagnant.

Current meteorological analysis suggests fairly widespread rain/thundershowers with isolated heavy falls likely over northeastern states during the next 48 hours and decrease thereafter. But indications are that the region is bracing for the onset of monsoon, pre-dating that over the southwest coast by a few days.