Severe cold in N-W may trigger ground frost

Ongoing cold to very cold spell over North-West and Central India is now fraught with an associated risk of ground frost over Jammu & Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, Punjab, Haryana, Chandigarh, Delhi, West Uttar Pradesh, Rajasthan and Madhya Pradesh during the next two days.

The cold spell will also be accompanied by strong surface winds speed reaching 10-20 km/hr adding to the frigid conditions. The wind chill factor would, in turn, lead to severe cold wave conditions during this period, said an India Meteorological Department (IMD) update on Friday.

Low mercury, ground frost

Dense fog combines with lingering moisture left behind by a western disturbance, which can either drift as thick fog or settle on ground as frost as temperatures take a dip after the western disturbance yields space to colder westerly to north-westerly winds from across the international border with Pakistan.

While low temperatures are good for the Rabi wheat crop, fog that persists for a week to 10 days could prevent radiative heating of the plant. This would make it vulnerable to pest attack and diseases. Farmers need to be wary of these conditions, more so if the low temperatures lead to ground frost.

‘Cold day’ (when maximum temperatures are 16 deg Celsius or below) to ‘severe cold day’ (wind chill factor coming into play) conditions may prevail over parts of Punjab, Haryana, Chandigarh, Delhi and West Uttar Pradesh until Saturday. A ‘cold day’ may prevail over the Jammu division, Himachal Pradesh, Uttarakhand, East Uttar Pradesh, Rajasthan and West Madhya Pradesh.

Dense fog in East

Dense fog is forecast over Himachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura on both Saturday and Sunday. While no significant change in day/night temperatures is expected over the North-West during the next 2-3 days, they may trend up during the subsequently, the IMD said.

Prevailing westerly winds would push the cold spell to Central and East India during this period. Night temperatures may fall by 2-3 deg Celsius over Maharashtra till Monday and rise thereafter. Shallow to moderate fog is expected over isolated pockets in Bihar, Odisha, Jharkhand, West Bengal and Sikkim.

North-East monsoon active

Meanwhile in the South, the North-East monsoon has been active over Tamil Nadu, Puducherry and Karaikal — thanks to prevailing easterly wave activity, the southerly counterpart of the western disturbance in the North, though operating in the opposite direction (East to West as against West to East).

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