Some call it as an impact of global warming, others describe it as vagaries of weather. But in any case, temperatures this winter, barring the first week of January, have constantly been 2-3 degrees above the normal in Northern and Central/Western India so far this winter, barring the hilly states of Kashmir and H.P.
According to the IMD, this year we have been receiving a steady stream of cyclonic circulations in January and February, which made the weather warm and at times cloudy but since moisture feeding has not been sufficient, the clouds have not precipitated into rains. But we can expect some change in the climate from Wednesday evening, with the advent of the W.D.
There are four weather systems at present hovering over north India. While a western disturbance has entered Rajasthan, secondary cyclonic circulations have been spotted over south Rajasthan and Uttarakhand . The movement of these four systems would determine whether it will rain and in which regions. Rains may occur in some parts of the plains of North India, if these systems move over Punjab and westwards towards Delhi and UP, and get sufficient moisture feed.
These western disturbances and cyclonic circulations are responsible for heavy snowfall in Kashmir and Himachal Pradesh. Leh recorded a minimum of -11.6c and Kargil -18c on the 1oth..
Normally, after causing rains or snowfall, these systems fizzle out and move away, to allow dry westerly winds to sweep plains, leading to cold wave in Central and Western regions.. However, during their short life period, these systems cut off the flow of icy winds to plains. It is only after these systems get weak that wind pattern changes and the chill sets in.
But this year, formation of cyclonic circulations have been more frequent and without any break in comparison to normal behaviour. As a result of which, dry icy winds did not get enough opportunity to lash the regions south of the regions of the W.D. Moreover, in the states of Punjab and U.P. since the moisture feeding was not sufficient, the successive secondary cyclonic circulations, could not generate enough intensity to precipitate into rains.