Early onset of summer in NW India despite La Nina’s cooling effect?
Summer seems to have arrived in many parts of northwest India. The maximum temperatures have started nearing and, in some cases, breaching the 35 degree C (°C)mark, 6 to 7 degrees higher than normal.
On Thursday, Delhi recorded 33.2°C, 8 degrees above normal; Narnaul recorded 34.5°C, 8 degrees above normal; Hisar 32.3°C, 6 degrees above normal; Churu 35.3°C, 6 degrees above normal; Narnaul 34.5°C, 8 degrees above normal; Ambala 31.1°C, 7 degrees above normal and Bikaner 34.6°C, 6 degrees above normal. According to the Thursday bulletin of India Meteorological Department (IMD), above normal temperatures will prevail across the country for the next 2-3 days.
On Wednesday, Phalodi, for example, recorded 35.8 degree C (°C), 6.8 degrees above normal; Bikaner 34.2°C, 7.2 degrees above normal; Churu 35.6°C, 7.6 degrees above normal; Pilani 34.5°C, 8.5 degrees above normal; Narnaul 34.5°C, 9.5 degrees above normal; Delhi recorded 32.5°C, 7.5 degrees above normal.
According to an IMD statement, higher temperatures over the north-western plains is mainly attributed to absence of any weather system, and prevalence of south-westerly surface winds which is causing advection of heat from West Rajasthan towards the region.
Interestingly, earlier meteorologists had projected that winter conditions could be prolonged this year because of La Nina, 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 the 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 Nino is associated with drought or weak monsoon while La Nina is associated with strong monsoon and above average rains and colder winters.
“La Nina conditions are still moderate. But I think temperatures have gone up in northwest India due to south-westerly winds. Northerly winds bring cool air. The maximum temperatures can drop again marginally and temporarily when the wind direction changes,” said DS Pai, senior climate scientist at IMD, Pune.
“Yes, there seems to be early onset of summer this year. The La Nina’s cooling effect has started diminishing. We have seen 30°C+ temperatures in the last week of February in the past also but this time the average maximum temperature is definitely higher. Normally, there are six Western Disturbances in January and February but this time, there was one Western Disturbance which affected between January 3 and 6 and another around February 4 which also impacted the northern plains. The impact of the rest of the WDs has been limited to upper reaches of Western Himalayas. There are clear skies and low wind speed which is leading to rapid heating in the day,” explained Kuldeep Shrivastava, head, regional weather forecasting centre.
“We are almost in summer. IMD considers March, April and May to be pre-monsoon season. The reason we are seeing a sudden shift to hot weather is because there is no weather system bringing rain. There is rain and snowfall only in the Western Himalayas. The wind direction is variable but mostly easterly. Whenever there is abundant sunshine there will be heating. We are preparing to issue our outlook for summer season next week,” said K Sathi Devi, head, national weather forecasting centre.