Heavy rainfall in a short span common in the national capital for the last couple of years, says IMD’s regional head
Western disturbances were responsible for heavy to very heavy rainfall in Delhi in the first fortnight of July 2023. Photo: Vikas Choudhary / CSE Heavy to very heavy rainfall in a short span of time has become the new normal during monsoons and national capital, Delhi, has also been affected this time. On July 26, 2023, 110.5 millimetres (mm) of heavy rainfall was recorded at India Meteorological Department’s (IMD) SPS Mayur Vihar station in just three hours — 5.30 am to 8.30 am.
Rainfall between 65 mm and 125 mm is classified as heavy by the IMD.
Rainfall was also recorded at other parts of the city, but at much lower quantities. A total of 53.5 mm of rain was recorded at Delhi's Mungeshpur station over seven hours, 2.30 am to 8.30 am. Safdarjung, the base station for Delhi, saw 36.5 mm rain from 5.30 am-8.30 am.
Two weather systems could be behind the disproportionate amount of rain in the east Delhi region, Kuldeep Srivastava, head of Delhi's regional India Meteorological Department, told Down To Earth (DTE).
The monsoon trough (extended low air pressure area) was spread from Ajmer, Rajasthan in the south to Madhya Pradesh on July 26, 2023 and spread towards the east. The easterly winds present in the monsoon trough carry a lot of moisture, which causes rainfall, said Srivastava.
At the same time, a western disturbance was also present around 70 degree and 32 degree latitude. Both these weather systems caused heavy rainfall in Delhi, especially in east Delhi and west Uttar Pradesh.
“The trend of receiving heavy rainfall (65 mm to 125 mm) in a very short time has been seen frequently in Delhi during the monsoon season,” Srivastava told DTE.
The monsoon trough is still active and remains in the south, which may move north in the next two days, said a July 27, 2023 press release by IMD. The centre of the low pressure area crosses Bikaner, Kota, Raisen, Durg and extends east-southeastwards to east-central Bay of Bengal and up to lower tropospheric level.
There may be another western disturbance in the future as well, which may lead to more rain in Delhi and surrounding areas.
Western disturbances are weakening in the winter, while their instances are increasing in the summer. They were responsible for heavy to very heavy rainfall in Delhi and including the hills, in the first fortnight of July this year as well.
However, local weather factors were responsible for the rainfall on July 26, Akshay Deoras, meteorologist and researcher at the Department of Tropical and Himalayan Meteorology at the University of Reading, United Kingdom, told DTE. “There was no effect of a western disturbance for the rainfall,” he said.
Deoras said the rainfall was normal. The deluge that happened early in the month, on the other hand, showed the effect of a western disturbance.
A strong local convection was passing through Delhi on July 26, which is now moving towards National Capital Region-western Uttar Pradesh, said SK Kant of IMD. “The convection led to the rain,” he said.
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