Vinson Kurian
Thiruvananthapuram, Feb 16 Weather-making western disturbances bound for northwest India are set to take a break with an ‘exchange of guard’ across the border by semi-permanent parent weather systems. A resident trough (low-pressure area) over Pakistan/Afghanistan has been setting off a train of rain and snow-producing western disturbances into northwest India during the best part of the month.
CPC DATA This is corroborated by the data put out by the Climate Prediction Centre (CPC) of the US National Weather Services showing precipitation estimated by satellites and expressed as a percentage of the seasonal normal. According to the CPC, precipitation recorded during February 1-13 has been above normal over north Konkan, parts of central Gujarat, eastern flanks of Jammu and Kashmir, north and east Rajasthan, Punjab, Delhi, east Uttar Pradesh and parts of east India adjoining the North-East.
The weekly statistics as on February 11 put out by the India Meteorological Department (IMD) is more or less in agreement. But rainfall was in deficit over most parts of the region during entire January which saw mercury climb up to unprecedented levels at many places.
During that month, above normal rains were confined to a narrow swathe along a northwest-southeast axis across Jammu and Kashmir and appearing to link Punjab and west Uttar Pradesh as well.
BREAKING UP The shift in fortunes in February was attributed to the building of the semi-permanent trough, which may be breaking up now. International models see a weak ridge (high-pressure area) area building around Afghanistan that would repel inbound westerly systems. But even this ridge formation is destined to die out over the next five days, if model forecasts are to be believed, which should once again make the way clear for western disturbances.
The first such system is forecast to roll in around February 19/20. Late on Sunday evening, the IMD too concurred with this outlook. The wet and cold/dry weather are shown to alternate, thereafter, and stay as such until the month-end.
MERCURY FLARE Meanwhile, a narrow strip where mercury is likely to flare up has been indicated eastward from west central India during the rest of the month. The maximum temperature level is expected to touch 40 deg Celsius over this stretch.
The ‘hot spot’ should get progressively concentrated to east-central (mainly the Andhra Pradesh-Orissa belt, and occasionally testing the fringes of east Madhya Pradesh, Vidarbha, Chhattisgarh and Jharkhand).
On Sunday, the IMD expected minimum temperatures to fall by 1-3 deg Celsius over northwest to adjoining west and central India as a prevailing western disturbance exits the region over a period of the next three days.
An induced cyclonic circulation traced to over central Pakistan and adjoining Punjab had since moved into over Punjab and neighbourhood. This is currently holding up the minimum mercury level over the northwest. It is expected to move away into the northeast, helping colder northwesterlies to fill the plains.
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