Cold wave conditions expected again in North India! After a small respite from the dropping night time temperature, the national capital is again expected to receive another phase of cold wave in the coming days. The minimum temperature during the night had suddenly dropped between November 16 and November 24 breaking the 17-year old record by reaching 6.3 degree celsius, the Indian Express reported. However, for the last four days, the mercury has risen up in the city but the weather department has said that Delhites should brace another bout of cold wave in the coming days.
What are the reasons for such recurrent cold waves?
One of the dominant reasons for the dip in the temperature is the occurence of snowfall in the hilly states of Himachal Pradesh, Jammu and Kashmir, and Uttarakhand in the recent days. Cold winds blowing from these regions is bringing the chill in the entire North Western Plains including the national capital. Heavy snowfall has been reported in the high altitude regions beginning from November 15 which explains the drop in the temperature in the North-Western plains of the country including Delhi.
According to the meteorological experts, the snowfall in the hilly states has been caused due to a Western disturbance(also known as extra tropical storm) which had also brought sudden drop in the temperature, cloudy skies along with a shower in Delhi on November 15. The cloudy skies hinders the path of the sunrays and reduces the insolation of heat on the ground further reducing the day time temperature.
What defines a cold wave?
IMD declares a period as a coldwave when there is a sudden drop in the night time or minimum temperature of an area. For regions lying in the plains, the IMD’s criteria for declaring a coldwave is the dip in the minimum temperature up to or below 10 degree celsius along with departure from normal minimum temperature by 4.5 degree celsius or more for two consecutive days. Except two days namely-November 16 and November 17- the night time temperature in the national capital has remained below normal for the entire November month this year.
Meteorologists have also said that the development of the La Nina climate pattern has also contributed to the chill in this year’s temperature. La Nina is an event during which large-scale cooling of the surface water of the central and eastern equatorial Pacific ocean is recorded which brings changes in the wind, pressure and rainfall in the surrounding regions.
In addition to the national capital, the regions in the vicinity of snowfall prone states such as Punjab and Haryana are also expected to experience a substantial drop in the temperature, according to the IMD forecast.