A passing western disturbance has intensified, as expected, as its southern flanks encountered the North Arabian Sea and threw up a low-pressure area (on top of a usual cyclonic circulation) over North-West Rajasthan, even as the parent disturbance has locked in over North Pakistan for now.
A late evening update from India Meteorological Department (IMD) on Thursday said the south-westerly winds from the ‘low’ and an accompanying cyclonic circulation have been fanning in lots of moisture from the Arabian Sea and will do the same over the Bay of Bengal as it travels East across East and North-East India.
Snow, showers for hills, plains
The moisture brought in by the western disturbance and the ‘low’ gets blown against the heights of the Himalayas further in North and North-East, and into the plains of North-West India cooled so far by the north-westerly winds, forming clouds. Shift in wind direction plus embedded moisture will translate into snowfall in the hills and showers/rain along the plains.
This is even as the cumulative rainfall so far for the country as a whole during the winter (January 1-February 2) logged in at 116 per cent above the long-period average, and as high as 122 per cent for North-West India alone. The latest week ending as on date signalled a break from a lean patch ending with deficits of 69 per cent and 96 per cent, respectively.
The bumper rain pattern may get to fluctuate even more into February and May as temperatures begin to look up and the country migrates into spring. However, the US National Centres for Environmental Prediction sees rains returning to parts of North, North-West and East India during the week from February 11-19.
Fairly widespread rain on Friday
The ongoing fairly widespread to widespread light/moderate rain may taper to being isolated over Punjab, Haryana, Delhi and Uttar Pradesh on Friday. The causative western disturbance and the induced ‘low’/cyclonic circulation are expected to move to the East or North-East as usual.
This phase would see its limb extending into the Bay and stirring activity with implications for weather over East and North-East India as westerlies from the western disturbance interact with southeasterlies from the Bay. Fairly widespread to widespread light/moderate rain and thunderstorms/lightning may continue to lash Bihar and Jharkhand on Friday.
A similar pattern is predicted for West Bengal, Sikkim and Odisha with possibility of isolated hailstorms on Friday. Isolated heavy rain may break out over Bihar, Jharkhand, West Bengal and Sikkim. Widespread light/moderate rain and thunderstorms/lightning may hit North-East India on Friday and Saturday.
Rains for North-East India
Isolated heavy rainfall/snowfall is forecast over Arunachal Pradesh these days; heavy rainfall over West Assam and Meghalaya and isolated hailstorms are expected over West Assam and Meghalaya on Friday. In the meanwhile, a fresh western disturbance, may troop into North-West India.
It may trigger isolated to scattered rainfall/snowfall likely over the hills of North-West India in Western Himalayan region on Sunday and Monday. Dense fog may descend over isolated pockets during night/morning hours over Punjab and and Haryana, Chandigarh and Delhi during the subsequent two days.