Wednesday, May 04, 2011
4pm, Isolated T.cell over N-E Tamilnadu, Heavy rain over S. bengal, Orissa-bengal border, Jharkand ... http://ow.ly/i/b7Yo
Heating trend may once again get briefly disrupted
Expectations of low-pressure area in the Bay of Bengal having subsided, the focus has once again shifted to the heating pattern in northwest India.
The heating in this geography has a crucial bearing on the strength and prospects of the impending southwest monsoon.
The highest maximum recorded in the country on Monday was reported from this region, but at 44.4 deg Celsius, it might just have failed to warm the cockles of hardened monsoon watchers.
The heating has admittedly been below par during the season until now and arrival by Thursday of a fresh but heat-killer western disturbance as forecast by India Meteorological Department (IMD) may pour cold water on any hopes of a smart pick-up in mercury over this region.
Sustained heating is required to set up the “heat low,” a peculiar atmospheric phenomenon special to this part of the world, that helps moisture-laden southwesterly monsoon winds march up north along the pressure gradient.
The IMD maintained its outlook for the westerly system on Tuesday morning, which would affect the western Himalayan region and adjoining plains of northwest India from Thursday.
As a result, scattered rain or thundershowers are expected to break out over the western Himalayan region, as per a short-term outlook valid until Friday.
Isolated dust storm or thunderstorm would occur over adjoining plains of northwest India during this period.
The IMD has said that no significant change is expected in maximum temperatures over northwest, west and central India. But even dust storms/thunderstorms can cap maximum temperatures by varying margins, even if temporarily.
Meanwhile, an upper air cyclonic circulation persisted over east Uttar Pradesh.
A trough from this system extended downward, but unlike until the previous day, was cut short over north coastal Andhra Pradesh. It ran through east Madhya Pradesh, Chhattisgarh and interior Orissa.
The other upper air cyclonic circulation, which was expected to father the “low” in the Bay, hung above central parts of south Bay of Bengal.
Satellite imagery early on Tuesday evening showed the presence of convective clouds over parts of east-central and south Bay of Bengal and southeast Arabian Sea.
A short-term outlook valid until Friday said that widespread rain or thundershowers would occur over Andaman and Nicobar Islands, scattered over south Karnataka, Kerala and Lakshadweep and isolated over rest of peninsular India.
Fairly widespread rain or thundershowers would occur over the Northeastern States.
Scattered rain or thundershowers would occur over sub-Himalayan West Bengal, Sikkim and isolated over the rest of east India.
An extended forecast valid until Sunday said that fairly widespread precipitation activity would unfold over western Himalayan region.
Isolated dust storm or thunderstorm could break out over the adjoining plains of northwest India.
Isolated rain or thundershowers would occur over the Northeastern States and adjoining east India.
Category:
IMD Report,
summer-11
South China Sea cyclone may launch monsoon into Bay
Global models indicate the possibility of a South China Sea cyclone helping launch the southwest monsoon into the Andaman and Nicobar Islands, its first port of call in the Indian territorial waters, around the normal date.
This is even as India Meteorological Department (IMD) has been keeping a watch for the first pre-monsoon low-pressure area to spring up in the Bay of Bengal. But a core of strong westerlies already blowing across the plains and into the Bay of Bengal may put paid to these hopes.
A fresh western disturbance is expected to check into western Himalayas and northwest India by Thursday and opposing flows from this may snuff out any chance of revival of full-fledged ‘low' in the Bay.
A weak circulation would likely be all that is left of the current churn in the Bay, which would be made to retreat east-northeast towards the Myanmar coast.
The IMD has withdrawn its watch for the “low” effective from the afternoon bulletin on Monday. It is in this backdrop that the forecast about the likely formation of a cyclone in the South China Sea by the European Centre for Medium-Range Weather Forecasts (ECMWF) assumes significance.
The “wet season” has already unfolded over Southeast Asia from Sunday (May 1), regional met agencies confirmed.
This is the usual date for the onset here and the winds would turn southwesterly as a “low” originating in the west Pacific crosses the Philippines and drifts into adjoining South China Sea.
The ECMWF expects this system to drop anchor here, and grow in strength to become a tropical cyclone by May 12, up to which its guidance is available. The US National Centres for Environmental Prediction expects this system to hurl a potent circulation into the Andaman Sea, or extreme southeast Bay of Bengal, during the week that follows.
This could also bring the southwest monsoon into Andaman and Nicobar region around the normal time for onset (May 15 to 20). It will take another fortnight for the Arabian Sea arm of the monsoon to make a splash over the Kerala coast
Category:
IMD Report,
South West Monsoon,
summer-11
Seems to be strong South west monsoon winds picking up strength over S. Bay along 5th parallel.. http://ow.ly/i/b7Fl
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