Heatwave to affect parts of country over the weekend
Clear skies almost all over the country, a change in wind patterns following cyclone Amphan as well as hot, dry north-westerly winds blowing over Peninsular India have made conditions favourable for heatwaves after an unusually pleasant spell of weather due back-to-back western disturbances, according to India Meteorological Department (IMD) scientists.
IMD on Thursday said there will be a 2-4 degrees Celsius rise in maximum temperatures over the country’s northwestern, central and western parts in the next two to three days. It has warned of heatwaves in Rajasthan (May 21-25); western Madhya Pradesh, Vidarbha and Telangana (May 21-24); coastal Andhra Pradesh, Yanam, north interior Karnataka, Tamil Nadu, Puducherry and Karaikal (May 21-23); eastern Madhya Pradesh, Rayalseema and Uttar Pradesh (May 22-25).
A heatwave is declared when the maximum temperature hits 45 degrees Celsius or is above 40 degrees Celsius in summer with a variation of five degrees or more above the normal temperatures.
IMD said a feeble western disturbance on Friday is likely to bring rain and thundershowers to Jammu & Kashmir, Himachal Pradesh and Uttarakhand and light thundershowers to Haryana, Punjab and Delhi. It added maximum temperatures, however, are likely to rise in the northern plains.
Western disturbances are low-pressure systems that generally originate over the Mediterranean region and are known to bring winter rain in India. Their intensity reduces in summer when they move to upper latitudes.
At 44.1 degrees C, Palam recorded the maximum temperature in Delhi on Thursday. It was the highest this season. At Safdurjung, the temperature was recorded at 42.7 degrees C, three degrees above normal.
According to private forecaster Skymet Weather Services, heatwave conditions are likely over Delhi and Haryana also after 2 to 3 days.
National Weather Forecasting Centre head K Sathi Devi said two important factors are responsible for the rise in temperatures. “...one is there is no clouding. There are clear skies almost all over the country except where the cyclone or depression is. The other reason is there is advection; wind patterns have changed after the cyclone.” Devi said hot, dry north-westerly winds were blowing even over the Peninsular India, which makes conditions favourable for heatwaves. “East MP [Madhya Pradesh], Rajasthan, UP [Uttar Pradesh], parts of Peninsular India are all likely to develop heatwave like conditions now. There is no major weather system that can cause clouding. The impact of western disturbances will also gradually reduce now leading to higher temperatures in northwest India including Delhi.”
Barmer (Rajasthan) and Aloka (Maharashtra) recorded the highest temperatures in the country on Wednesday (44.2 degrees C).
Sunita Devi, the in-charge of cyclones at IMD, said, “Because of the cyclone, all the moisture is concentrated around it while dry, north-westerly winds are blowing over the rest of the country, which causes temperatures to peak gradually.”
Even June is expected to be very hot in parts of the country. “If there is no western disturbance, NW [north western] India will be hot even in June. Hot winds from desert regions will heat up the region as wind patterns have changed after Amphan,” said D S Pai, a senior scientist at IMD, Pune.
Amphan led to an early onset of the monsoon over the Andaman and Nicobar Islands on May 17. A low pressure before the formation of Amphan made conditions favourable for the advancement.
The onset of the monsoon over Kerala is likely to be delayed by four days and is expected to arrive on June 5, IMD said last week. It marks the beginning of the four-month rainy season when India receives 70% of its annual rainfall. IMD’s south-west monsoon forecasts provide information to at least 700 million people in India, who are dependent on agriculture for livelihood. The delay could have implications for farmers impacted by an economic slowdown associated with the Covid-19 pandemic and the lockdown.
The monsoon is crucial for the yield of rice, wheat, sugarcane, and oilseeds in a country where farming accounts for about 15% of the economy but employs over half of its people.
M Mohapatra, director-general, IMD, said after a cyclone passes, the atmosphere is disturbed. “It takes time to come back to normal. Monsoon advancement can begin normally only when normal atmospheric and wind conditions are restored. The westerly hot winds also impact most parts of the country.”