Not a single ‘cold wave’ this time: Delhi experiences one of its warmest winters in a decade
With hardly any rain, not a single ‘cold wave’ or ‘cold day’, and higher than normal average day temperatures, Delhi is currently experiencing one of its warmest winters in the past decade.
Experts said this is because of lack of western disturbances that bring rain in the plains and snow in the hills.
The Indian Meteorological Department’s (IMD) data shows that while the average day temperature of January 2018 (till January 17) is the highest in 10 years, December 2017 was the second warmest December month since 2008 after December 2016.
“The IMD stated in its long range winter forecast that the maximum and minimum temperature will be higher than normal this year particularly for the northern states, including Delhi. There would be fewer cold waves,” said a senior official of the National Weather Forecasting Centre (NWFC).
The average day temperature of December 2017 was 24.08 degrees Celsius, while that of December 2016 was 24.5 degrees Celsius. “Last time Delhi witnessed such high average day temperature in December was in 2008 when it was recorded at 24.5 degrees Celsius,” said a senior official of the Regional Weather Forecasting Centre (RWFC).
The average day temperature of January 2018 (till January 17) was 21.7 degrees Celsius, while that of January 2017 was 21.1 degrees Celsius. Last time the average day temperature in January was so high was in the year 2009 when it touched 21.7 degrees Celsius.
“It is usually the plummeting maximum temperature that gives us the chilly wintery feeling during day time. We hardly get to feel the night temperature as it is recorded before sunrise,” said Kuldeep Srivastava, a senior scientist with the RWFC.
When the maximum temperature falls at least 4.4 degrees below the climatic normal then it is termed as a ‘cold day’. If it falls more than 6.4 degrees from the normal, it is termed as a ‘severe cold day’.
“Delhi did not witness such cold days in December 2017 or December 2016. In January 2017, Delhi witnessed a few spells of ‘cold waves’ — a condition when the night temperature drops below four degrees Celsius. But this January we are yet to see any cold wave,” said a senior official from the MeT department.
Western disturbances and chilly winds
The official attributed the comparatively higher temperature this winter to fewer number of western disturbances, which trigger rain in the plains of northwest India and snow in the hills.
“Usually northwest India receives around 2-3 such disturbances in December and 3-4 in January. But this time there was just one in December which triggered rain on December 11. The mercury dropped by around five degrees. In January, however, Delhi has not received any such storms till now,” said Srivastava.
In December and January, Delhi usually receives around 9.4 mm and 19.3 mm of rain respectively triggered by western disturbances. But this time while there was around 7.8 mm of rain in December and it has not rained yet in January.
Moreover, most of the hills stations in Himachal Pradesh and Uttarakhand hardly received snow.
“Delhi usually gets the chill when the snow melts in the hills and the northerly winds bring in the icy cold winds. But with less snow this time, Delhi missed the chill,” Srivastava added.
MeT officials said that a western disturbance is likely to trigger rain and thunderstorm on January 23 which could result in a drop in temperature. “But it could be the (first and) last time that Delhiites get to feel the chill as the temperature will start shooting up from February,” said a senior MeT official.