At a time when many parts of the country are reeling under a sweltering heatwave, several areas in Bengaluru received heavy rainfall, accompanied by lightning, thunder and in some cases, hailstones, on Sunday.
The India Meteorological Department (IMD) has forecast rain/thundershowers for the next 48 hours in Bengaluru.
What is causing these thunderstorms amidst severe heatwaves?
“This is the season for severe heat-induced thunderstorms to occur in this part of India,” said Dr Geeta Agnihotri, Scientist-F at IMD Bengaluru, referring to the southern peninsula.
“And if large-scale weather features are present, the severity (of the thunderstorms) increases exceedingly.”
High wind speed and hailstorms are some of these weather features, she added.
Also read: Sudden showers pile misery on Bengaluru
A trough running from Vidarbha to South Tamil Nadu across Telangana and Rayalseema is adding to the severity of the thunderstorms, she explained. A trough is a long area of low air pressure between two areas of high air pressure.
Dr Agnihotri expects this weather pattern to continue for the next two days in Bengaluru and most of South Interior Karnataka.
Talking of the hailstorm, she said though the IMD’s three observatories in Bengaluru didn’t report it, they were able to verify it through crowdsourcing.
The maximum temperature, which had hovered around 36°C just a few days ago in the city, dropped by at least two degrees. At 5.30 pm on Sunday, it was 33.9°C in the city and 33.1°C at the HAL airport.
Observation data recorded by the IMD showed that the HAL airport received 26 mm of rainfall from 8.30 am to 5.30 pm. This figure was 11.2 mm for the city observatory and 5.4 mm at the Kempegowda International Airport.
As a result of the thunderstorm, there was a sharp drop in mercury.
The Kempegowda International Airport, on the city’s northern outskirts, was a tad hotter at 35.7°C, according to the IMD official.
How do hailstones form?
Hailstorms generally take place amidst thunderstorms. Atmospheric sciences scholar G. Brant Foote, explains in the Journal of Applied Meteorology that in order for hail to form there must be strong updrafts in a storm.
"In the middle levels of the storm, water droplets are carried to higher elevations by strong updraft currents. Eventually, the droplets freeze into a tiny crystal known as a hail embryo, or graupel. This process takes ten to sixteen minutes. If the storm is cold enough to freeze water, hail is likely to develop. Hail rarely forms in the warm tropics because it is typically much too warm. The more moisture present in a storm, the easier it is for hailstones to grow," Foote's theory as cited by James MacDonald says.
On social media, many residents of southern and eastern parts of the city posted photos and videos of the hailstorm. Elsewhere, it was a thunderstorm accompanied by lightning.
The hailstorm was reported from BTM Layout, Koramangala, Hosur Road, Bommanahalli, HSR Layout, and KR Puram.
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