Delhi caught napping! Rain brings the good, the bad, and the ugly as weathermen fail to gauge intensity

NEW DELHI: If the intense thunderstorm and heavy rain early Friday morning caught Delhi-NCR residents by surprise, they were not alone. Even the India Meteorological Department failed to gauge the strength of the storm and rain in advance.
As late as 2.30am Friday, IMD's nowcast for the subsequent 3 hours predicted 'light rain/thunderstorm/dust storm' in most areas of Delhi/NCR. In the event, this was the severest period of the storm, with Safdarjung recording 60mm of rain during these three hours with windspeeds gusting up to 80kmph.

With 17mm more logged in the next three hours till 8.30am, the 24-hour rainfall of 77mm was not just the second-highest for May since 1901, it was also the wettest day in the capital in over eight months since 77.1mm was recorded on Aug 29, 2024, during the monsoon season.
"We had forecast the rain spell in the region a few days in advance but we couldn't predict the intensity of the storm that struck Delhi-NCR on Friday morning," admitted IMD chief Mrutyunjay Mohapatra.
"Thunderstorms are difficult to predict in long and medium range forecasts. These are usually captured in nowcasts issued a few hours in advance. When an orange alert is issued, it should be taken seriously. It's a signal for people to be alert to possibility of extreme weather," Mohapatra said.
This time around, however, the orange alert was issued by IMD only around 2.30am, when very few people were awake to see it. Due to the sudden and complex nature of thunderstorms, their intensity is difficult to predict. Also, thunderstorms of such intensity are very rare in north India at this time of the year.
So, what led to the severe thunderstorm on Friday in north India? It was a perfect convergence of all factors that cause such an event, the expert said.
"You need four parameters to come together for a thunderstorm - a period of intense heat, sufficient moisture in the atmosphere, unstable atmospheric conditions and, finally, a trigger that sets it all off," the IMD chief said.
In this case, intense heat was seen in Rajasthan, particularly its western part. "As for moisture incursion, usually in northwest India it comes from Arabian Sea. But this time, moisture also came in from Bay of Bengal, pulled in by two cyclonic circulations over Rajasthan," Mohapatra said.
He said adding to the atmospheric disturbance were strong westerlies in the upper atmosphere at a height of 6 to 12km, blowing at over 120kmph.
"Then there was a western disturbance that acted as a trigger. The confluence of these strong factors made it a very potent storm," Mohapatra added.