Temperature in May likely to be over 42° C, predicts IMD
The India Meteorological Department (IMD)’s long-range forecast for May indicates most parts of northwest, central and east India will record maximum temperatures of over 42 degrees C in the second, third and fourth week of May.
But that may not be the case for northwest India if western disturbances (WDs) continue to affect the region as they have in March and April. There will be several cloudy days and thunderstorm activity, which will keep maximum temperatures down by 2 to 3 degrees, if the current pattern of WDs continues.
IMD scientists said the climate models used for long range forecast of seasons cannot account for the impact of WDs, which can significantly alter weather patterns in northwest India and even in other parts of the country depending on their intensity. They are highly unpredictable and are best tracked only three to four days in advance. So summer temperatures over India this year will continue to remain unpredictable.
“These models don’t factor in western disturbances. WDs usually affect only the northern part of the country in winter. This time we are seeing some intense WDs even in May, which is unusual. May and June are still there, let’s see how WDs affect the temperature in the rest of summer,” said M Rajeevan, secretary, ministry of earth sciences.
Rains over India during the pre-monsoon period from March 1 to May 4 have been 24% excess while over NW India it has been 41% excess and 174% excess over Central India. Such wet conditions over NW India during the pre-monsoon period is unusual. “We are expecting temperatures to be above normal over NW India and normal and slightly above normal over the rest of India. We can’t now talk about the impact of WDs because they can be forecast only three to four days in advance. By May, moisture is expected to reduce over NW India, which then leads to high temperatures but if there is moisture incursion from the Bay of Bengal or Arabian Sea, this will also change,” said DS Pai, senior scientist at IMD Pune. IMD uses statistical and dynamic models with various atmospheric and oceanic parameters to assess seasonal weather patterns.
Another IMD scientist who preferred not to be quoted said intense WDs have had an impact all over the country this year. This could not be captured in IMD’s seasonal forecast. “We have had only two to three occasions of heat waves in the Vidarbha region of Maharashtra. In previous years, heat waves began in early April. The combination of easterly winds, western disturbances, moisture incursion has changed everything. April and early May are cooler than normal,” he said.
WDs 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.
The IMD, in its Monday bulletin, said convergence of moist easterly winds can cause widespread thundershowers over entire northwest India over the next three days.
Thundershowers are also likely over Assam, Meghalaya, Nagaland, Manipur, Mizoram. Tripura, sub-Himalayan West Bengal and Sikkim during next three or four days. Thundersqualls (50-60 kmph) and hailstorms are also likely over parts of east India.
Experts at Public Health Foundation of India (PHFI) advised that the elderly will need extra care during extreme summer heat because of the combined threat of Covid-19 and heat stress. “Most people are indoors because of lockdown related restrictions. If power supply is ensured, this summer may be different and better. But due to less pollution, radiation will be high this year. These impacts will have to be studied,” said Abhiyant Tiwari, research associate at Indian Institute of Public Health.
The IMD, in its seasonal outlook for March, April, May, and again in an updated outlook for April to June season, had predicted that seasonal average maximum temperatures are likely to be warmer than normal by 0.5 to 1 degree C over northwest India and western peninsular India.