The India Meteorological Department (IMD) has attributed the frequent and prolonged spell of heatwave in April to absence of active western disturbances (WD) during the month.
According to the IMD, the absence of active WDs in April over north India caused highly subdued rain and very less thunderstorm activities over northwest and central parts, leading to frequent and prolonged spell of heat wave to severe heat wave days and higher-than-normal temperature over these areas on most days.
West Rajasthan, Himachal Pradesh, south Haryana-Delhi, west Madhya Pradesh and western parts of Uttar Pradesh experienced higher number of heat wave days and east Uttar Pradesh, east-central India reported lower number of heat wave days.
Overall, the month recorded six WDs (April 1-4, 7-9, 13-15, 20-22, 23-25 and 28-29).However, most of them were feeble and dry and moved across higher ridges of Himalayas. Only last three systems caused gusty winds and dust-raising winds and dry thunderstorms in some places in northwest, it said. Over Northwest India during April, the average maximum temperature was highest ever with 36.32 degrees Celsius in last 122 years against earlier record of 35.4 degrees Celsius in 2010.
The average mean temperature was highest ever in 2022 with 28.18 degrees Celsius against earlier record of 27.79 degrees Celsius in 2010. The minimum temperature was second highest with 20.04 degrees Celsius after the year 2010 (20.18 degrees Celsius). Over Central India during April, the average maximum temperature was highest with 38.04 degrees Celsius in the last 122 years for period 1901-2022 against earliest record of 37.75 degrees Celsius in 1973.
Similarly, the average mean temperature was in April 2022 highest with 31.35 degrees Celsius for period 1901-2022 and it broke earlier highest record of 31.10 degrees Celsius in 2010. The average minimum temperature was highest in April 2022 with 24.66 degrees Celsius and it broke the earlier record of 24.52 degrees Celsius in 2010. The monthly average minimum temperature over East & Northeast India for month of April over East & Northeast India was third highest with 21.94 degrees Celsius since 1901.
West Rajasthan, Himachal Pradesh, south Haryana-Delhi, west Madhya Pradesh, and western parts of Uttar Pradesh experienced higher number of heat wave days and East Uttar Pradesh, east-central India reported lower number of heat wave days.
Meanwhile, in contrast to the month of March 2022, northeast India, and southern Peninsular India, especially Kerala and Tamil Nadu, received scattered to fairly widespread rainfall and thunderstorms on many days in April 2022.
"It is mainly due to the fact that two cyclonic circulations moved from southwest Bay of Bengal to Southeast Arabian Sea across south India during 2nd and 3rd week and north-south troughs/wind discontinuities prevailed from Central India to South Peninsula in the lower tropospheric levels on many days."
Under the influence of cyclonic circulations/troughs in lower tropospheric levels supported by moisture incursion into the area there was fairly widespread to widespread rainfall/thunderstorm activity over Sub Himalayan West Bengal & Sikkim on most of the days and over Northeast India during the 1st half of the month.