Weather experts weigh in on why spring gave Delhi a miss
Delhi recorded a maximum temperature of 31.7 degrees Celsius on Saturday, Mumbai, 34.6 degrees, and Kolkata, 35.8 degrees as many parts of India experienced the hottest spring they have in years as the absence of western disturbances, cyclonic storms originating in the Mediterranean more than offset the effect of La Niña, which many experts expected to prolong the winter in the northern plains.
There might be a respite for a few days, from Sunday to the middle of next week, but it isn’t expected to be much of one, and then, forecasters say, it will heat up even more.
Since Monday (till Saturday), maximum temperatures in Delhi have read: 28.9; 31.5; 32.5; 33.2; 33; and 31.7 degrees C.
The situation is similar in most cities in the northern plains. Mumbai’s maximum temperature over the same period has ranged between 33.9 and 36.1 degrees C. These are between 5 and 7 degrees higher than normal. How unique is this? According to India Meteorological Department’s data, Delhi’s maximum temperature didn’t touch 30 degree C in 2020, 2019, 2015, 2014 and 2013 in February. There were 4 days with 30 degree C + maximum temperature in 2018; three days in 2017; and five days in 2016.
“Normally, six western disturbances impact the northern plains in January and February and about four to five in March. The north westerly winds bring pleasant spring time weather as we head to summer. That hasn’t happened this year. Only one WD each impacted the NW plains in January and February each. Rest of the WDs impacted only the upper reaches of the Western Himalayas. Warm south-westerly winds have been blowing,” said Kuldeep Srivastava, head, regional weather forecasting centre, IMD.
There is likely to be a marginal fall in maximum temperatures starting Sunday for a brief period which will not be as pleasant as spring, he said, adding: “Today the wind direction switched for a bit to north westerly (from the direction of Western Himalayas which normally brings cooler air).” The change may result in a 2-3 degree C drop in maximum temperatures over the plains till March 3. “But maximum temperatures are already 5 to 6 degree C above normal, so a 2-3 degree C drop won’t bring back spring. From March 3, maximums will rise again to 34 to 35 degree C,” Srivastava said.
According to an IMD statement on February 24, higher temperatures over northwestern plains can be attributed to absence of any weather system and prevalence of southwesterly surface winds, causing advection of heat from west Rajasthan towards the region.
Earlier, meteorologists expected winter to be prolonged this year because of La Niña, a global weather phenomenon. El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean, according to National Oceanic and Atmospheric Administration (NOAA).
ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. El Niño has a warming influence on global temperatures, while La Niña has the opposite effect. In India for example, El Niño is associated with drought or weak monsoon while La Niña is associated with strong monsoon and above average rains and colder winters.
On Friday and Saturday maximum temperatures over NW India were 6 to 8 degree C above normal. On Saturday Hisar recorded 31.5,five degree C above normal; Narnaul 33.8, eight degree C above normal; Churu 33.9 degree C, five degrees above normal; Ambala 30.3, seven degrees above normal; Pilani 33.7, seven degrees above normal; Karnal 30, six degrees above normal; Jaipur 33.8, six degrees above normal; Delhi recorded 33 degree C, seven degrees above normal on Friday and 31. 7, six degrees above normal on Saturday. Other central and eastern Indian cities are also seeing an early summer.
“The rise in maximum temperatures over northwest India is mainly due to south-westerly winds and the lack of weather systems which can bring rain. There has been snowfall and rain in the Himalayas on Friday so now temperature will fall temporarily but climatologically temperatures will continue to rise. In IMD’s terminology there is no spring. We move over to the pre-monsoon season from winter,” said M Mohapatra, director general, IMD. And some parts of India will heat up faster than the rest.
“Temperature starts rising peaking first in Odisha, Maharashtra, etc, in March and then in northwest India. So, we are also expecting temperatures to rise in Maharashtra from next week,” he added. “La Niña conditions are still moderate. But I think temperatures have gone up in northwest India due to south-westerly winds,” said DS Pai, senior climate scientist at IMD Pune said on Wednesday.