Incident last happened 62 years ago in 1961, confirmed IMD
The global warming effect, thanks to climate change and a trigger by Cyclone Biparjoy, is believed to have brought the monsoon to Delhi and Mumbai simultaneously on June 25, 2023, an event that has recurred after more than six decades.
On June 25, the southwest monsoon advanced over Mumbai and Delhi simultaneously, said the India Meteorological Department (IMD) in a bulletin.
Cyclone Biparajoy hit the western coast of the country on June 16. Several experts pointed out that it played a key role in the overlapping of the monsoon in Mumbai and Delhi. Some climate experts have also mentioned the El Nino factor.
“Today, June 25, the monsoon has arrived in both Mumbai and Delhi simultaneously; It previously happened on June 21, 1961,” said DS Pai, an IMD monsoon expert.
The monsoon normally arrives in Mumbai on June 11 and Delhi on June 27, according to long-term assessments by IMD. This indicates that the monsoon this year arrived in the national capital just ahead of schedule, while it was almost two weeks late for Mumbai.
“The monsoon circulation was weak in the Arabian Sea earlier, but the circulation was strong in the Bay of Bengal. However, now both have gotten stronger and have spread across the country,” pointed out Mrittunjoy Mahapatra, director general of IMD, to this reporter.
Cyclone Biparjoy had slowed down the monsoon circulation in the Arabian Sea, observed KJ Ramesh, former director general of IMD. However, the circulation was always strong in the Bay of Bengal.
The anomaly may have led to the unique situation this year, he said.
“The Arabian Sea has been warming since January as part of the global warming pattern,” explained Raghu Murtugudde, an earth scientist and weather expert attached to the Indian Institute of Technology, Mumbai and University of Maryland, on June 26.
Typhoons Mawar and Guchol were formed and Mawar became exceptionally strong for a May typhoon also because of global warming. Both typhoons pulled winds and moisture from the Indian Ocean, which delayed the onset of the monsoon, Murtugudde said.
“The typhoons also created weak winds over the Arabian Sea, which allowed cyclone Biparjoy to form very late and last very long, especially due to the Arabian Sea warming,” he said.
Biparjoy, in turn, disrupted the monsoon winds, created a delayed arrival of the monsoon over Mumbai and favoured heatwaves over central India, Murtugudde added.
“Cyclone Biparjoy also pulled the eastern part of the monsoon trough north and caused a slightly early arrival of the monsoon to Delhi on the same date,” pointed out Murtugudde.
Incidentally, at least three cyclonic systems affected the region in 1961 as well, when Mumbai and Delhi received the monsoon on the same day, according to IMD sources.
At least two frontline climate scientists observed the El Nino phenomenon might have played a role in the development as well.
“The monsoon onset was weak and the progression was delayed, an indication of the potential effect of El Nino. At the same time, there were rains in Delhi and north India early in the season owing to the cyclone remnants,” said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology.
This might have led to recycled moisture over this area, assisting the monsoon to reach there, but we need to look at it closely before drawing any conclusions, Koll said.
“It seems the Arabian Sea branch was a bit weak in the initial part of June. El Nino after three consecutive years of La Nina could be a reason but is difficult to pinpoint as yet,” said professor Subimal Ghosh at the IIT Mumbai, a climate scientist.
Ghosh is also one of the lead authors of the Working Group I for the latest United Nations climate report, Assessment Report 6, prepared by the Intergovernmental Panel on Climate Change, a scientific body under the UN.
“The southwest monsoon has further advanced into some parts of Gujarat, Rajasthan, Haryana, Punjab and remaining parts of Jammu, Kashmir and Ladakh today, June 26,” stated the IMD bulletin.
Portions of these states that have yet to receive monsoon rains would likely have them within two days, the notice added.
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