: It was the most hyped weather event in Delhi-NCR this year. So, when Tuesday’s thunderstorm that was billed to “wreak havoc” in the region passed the city by with a whimper, many people vented their anger on the Metdepartment. But here are five things you should know before putting the blame on the Met office.
One, the department didn’t get it very wrong. In its warning released on Sunday (May 6) the regional Met office had forecast “very light rain/drizzle accompanied with strong gusty winds” likely over Delhi and NCR on May 7 morning. For Tuesday, it said a spell of light rain/thundershowers accompanied with squall (wind speed exceeding 50kmph) was likely.
The word “likely” carries a 26-50% probability. The wind speed prediction of 50kmph meant it was not expected to be a severe storm. Met officials also said as much in the media. However, what weighed heavy on the minds of governments and other agencies issuing advisories was the damage wrought by severe thunderstorm events of the previous week in which 129 people had perished.
Two, thunderstorms, squalls and dust storms are very localised weather events. So, don’t expect to know exactly when a storm will hit well in advance. Typically, a single thunderstorm affects an area of 10-20sq km and lasts for up to three hours at most. “A thunderstorm is a mesoscale event caused by charging of particles due to friction. The only weather phenomenon that’s even smaller in scale is a tornado. One storm can give rise to another over an adjoining area and so on, making thunderstorms ‘travel’ over a larger area,” said M Mohapatra, DGM, India Meteorological Department.
Due to its very small scale, it’s not possible to capture the time and location of a thunderstorm one or two days ahead of the event.
Three, short-range weather forecasts, which predict weather for up to three days, give the probability of storms occurring over a wide area. IMD’s initial storm warning was based on this forecast. These were updated with shorter duration forecasts. “For the May 2 storms, which caused a lot of damage, IMD’s bulletin of April 30 had identified the potential area where the storms could strike. On May 2, we added squall to the warning. More specific district-level forecasts were also issued,” Mohapatra said.
Incompetent authorities just wanted to gain some media mileage and show the country they are also one of the Department in operation (for no good). They must have passed the entrance exams through grace marks.Parvin Sinha
Four, storms are most accurately captured in nowcasts, which predict conditions likely to develop in the next three hours using radars. The Met office had, in fact, issued nowcast alerts before the dust storms on Monday night and Tuesday afternoon. “IMD uses the services of 27 radars across the country to issue nowcasts for 399 Indian cities and towns. It’s new concept and we are getting better at it,” Mohapatra said.
Five, perhaps there is a case for IMD to use language that’s more easily understood by most people and conveys its forecasts more accurately. However, the hype and hoopla over the event was purely beyond its control.