Sunday, November 29, 2009

Colder conditions set to continue in North, central parts

Mercury is seeking new lows in North India as cold north-westerlies continued to blow across the international border on Friday.

An India Meteorological Department (IMD) update said that the cold to increasingly colder conditions are set to prevail over north, northwest and parts of central India until November 30.


A seasonal anti-cyclone (high-pressure area marked by clockwise winds, sinking air motion and clear skies) sitting smack over central India in the higher levels of atmosphere has been boosting the flow of westerlies to northwesterlies.

This anti-cyclone is seen lying extended to the east over Southeast Asia and China as well as into the Far-east over the Pacific facilitating the northern hemisphere winter.

What would expectedly reverse, if ever slightly, is the arrival of a western disturbance over northwest India by November, a remainder circulation from a large weather system that dropped heavy rains over West Asia on Thursday.

The western disturbance represents a trough of lower pressure (marked by anti-clockwise winds, ascending motion of air, presence of moisture and clouds) that warms up the atmosphere. This can help reverse the cold conditions at a given point of time.

Western disturbances often feature induced cyclonic circulations as they drift into northwest India and are known to help whip up additional moisture from the Arabian Sea to rain down over the hills and plains.

The IMD update on Friday said that maximum temperatures were above normal over parts of peninsular India, Madhya Pradesh and below normal over parts of Punjab and Bihar.

Minimum temperatures were below normal over many parts of east India, Jammu and Kashmir and Punjab. They were above normal over remaining parts of the country except over extreme south peninsular India where they are near normal.


No significant change in minimum temperatures is expected over the Indo-Gangetic plains during the next five days except a slight fall on Saturday and slight rise from Monday coinciding with the arrival of the western disturbance.

Meanwhile, towards the south, Thursday's cyclonic circulation over southeast Bay of Bengal persisted and is likely to move slowly west-northwestwards (towards Sri Lanka-India coasts). The weak northeast monsoon conditions are likely to continue over south peninsular India during the next three days as well.

But things may begin to look different from Monday with the west-northwestward-bound cyclonic circulation expected to impact coastal Tamil Nadu and Sri Lanka.

According to the US National Centres for Environmental Prediction (NCEP), the wet session marked by mainly widely separated rain or thundershowers may hold until December 4.

Its outlook for the December 5 to 13 too shows a calibrated rise in activity over the peninsular seas with a flare-up indicated close to the Tamil Nadu coast.

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