IMD predicts cold wave in north India for next two days
A cold wave is likely over some parts of Punjab, Haryana and northern Rajasthan in the next two days, India Meteorological Department warned on Monday. It will be the first cold wave this season. The weather office declares a cold wave when the minimum temperature drops below 10 degrees Celsius or is 4.5 degrees lower than the season’s normal for two straight days. A cold wave is also declared when the minimum temperature is less than 4 degrees in the plains.
The minimum temperature in Delhi fell to 9.6 degrees on November 17, and 9.8 degrees on Sunday, 3 degrees below normal on both instances. “Minimum temperatures are likely to dip in Delhi but cold wave is not likely. Cold wave may be recorded in Haryana and Punjab,” said RK Jenamani. On Monday, the minimum temperature was 11.4 degrees. Hisar in Haryana recorded 7.2 degrees on Monday, 4 degrees below normal.
“There are two ways by which the temperature falls. One is a clear sky, which leads to the warmth radiating back quickly from the surface. It’s called radiational cooling. There are clear skies over northwest India now,” explained DS Pai, scientist and head of climate research and services at IMD Pune. “The other reason for cold setting in is that northwesterly cold and dry winds are blowing over the region from the Himalayas. There is a low pressure area over Arabian Sea which also indirectly helps in incursion of northwesterly winds over the entire northwestern region. This happens during winter. Consecutive low-pressure areas have formed over the Arabian Sea,”
A cyclonic circulation is lying over southeast Bay of Bengal and its neighbourhood in the lower tropospheric. It is likely to move west-northwestwards towards the Tamil Nadu coast in the next 4-5 days. A trough (line of low pressure) is running from the cyclonic circulation over southeast Bay of Bengal and its neighbourhood to the Tamil Nadu coast. In association with the cyclonic circulation, moderate to heavy rainfall is likely over Karnataka, Kerala, Mahe, Tamil Nadu, Puducherry and Karaikal during the next five days, IMD predicted.
“We are expecting cold air incursion. In Delhi, there may not be a cold wave condition, but minimum temperatures will fall to about 8 to 9 degrees, around 3 to 4 degrees below normal,” said RK Jenamani, senior scientist at IMD. “In rural pockets, cold wave conditions are likely to set in.”
Currently, weak La Niña conditions are prevailing over equatorial Pacific Ocean. Latest weather forecast is indicating that La Niña conditions are likely to strengthen and peak to moderate conditions during winter. Thereafter, La Niña conditions are likely to start weakening to reach to cold ENSO neutral conditions during second quarter of the next year, according to IMD’s ENSO bulletin for November.
“La Nina conditions are associated with colder winters over northwest India,” said Pai. El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across equatorial Pacific Ocean, according to the National Oceanic and Atmospheric Administration (NOAA).