May temperatures to be unrelenting across north, west India

April temperatures over northwest and central India were the highest since 1900 and May too is likely to see above normal temperatures over north and west India. The rest of the country is unlikely to see levels touched in March and April, according to the India Meteorological Department (IMD).

“During May, above normal minimum temperatures are likely over most parts of northwest, central, east and northeast India. Normal to below normal minimum temperatures are likely over the south peninsular India and few pockets of northwest India,” the weather agency said in a statement on Saturday.

Heatwaves in May are likely to persist over Rajasthan, Gujarat, Delhi, Haryana, Punjab, Jammu and Kashmir, Ladakh, Mrutunjay Mohapatra, Director-General, IMD, said at a press briefing.

April this year has been India’s fourth hottest since 1901 while northwest and central India regions experienced their warmest April in 122 years. During April 1 to 28, the average monthly maximum temperature over northwest India was 35.9 degree Celsius and the same over central India was 37.78 degree Celsius, he explained.

Heatwave

A heatwave is declared when the maximum temperature is over 40 degrees Celsius and at least 4.5 notches above normal. A severe heatwave is declared if the departure from normal temperature is more than 6.4 degrees, according to the IMD. Based on absolute recorded temperatures, a heatwave is declared when an area logs a maximum temperature of 45 degrees Celsius. A severe heatwave is declared if the maximum temperature crosses 47 degrees.

Several parts of north and west India have seen temperatures routinely above 42C.

India continues to be singed by a string of heatwaves since late March, largely due to the absence of rain-bearing strong Western Disturbances, or tropical storms that bring rain from the Mediterranean over north India. Cool temperatures in the Central Pacific, or a La Nina, that normally helps rain in India too have failed to bolster rainfall.

Emerging Western Disturbance

The IMD weather models, however, suggest that there could thunderstorms from the middle of May due to an emerging Western Disturbance. “There were five Western Disturbances that formed in April but none of them were strong enough and therefore didn’t bring significant rain,” noted Mr. Mohapatra. He added that it was relatively unusual for heatwave conditions to prevail over India despite La Nina conditions.

A region of high pressure had built up that along with clear skies and reduced soil moisture meant hight temperatures.

May would also see above normal rainfall over south, central and eastern India but the base rainfall in this month being low, it would be insignificant over most of central and western India, he observed.

The IMD has forecast a ‘normal’ monsoon or 99% of the Long Period Average (LPA) of 87 cm and is expected to forecast the monsoon’s arrival over Kerala later in May.