The World’s Heaviest Hailstone Weighed Over A Kilogram – How Do They Get So Big?

On April 14, 1986, the Gopalganj district in Bangladesh was hit by a deadly hailstorm that would kill 92 people. According to the World Meteorological Organization’s World Weather and Climate Extremes Archive, the hailstones that fell from the sky that day weighed as much as 1.02 kilograms (2.2 pounds), earning the giant balls of ice a grim world record.

Giant hailstones still fall today, and we could expect more in future as climate change brings with it a higher frequency of extreme weather events. To help the world prepare for extreme hailstorms in the future, a new study looked at giant balls of ice that fell from the sky during a deadly storm in Catalonia in 2022, to see if they could work out how they develop to be so large.

Fortunately for science, local residents in Catalonia stored some of the giant hailstones in their freezers. The biggest of these behemoths were as much as 12 centimeters (4.7 inches) in diameter, and they gave the team the opportunity to use a new technique for studying hail.

“We wanted to use a technique that would provide more information regarding the internal layers of the hailstones, but without breaking the samples,” said senior author Professor Xavier Úbeda, a researcher at the University of Barcelona, in a release. “We didn’t expect to obtain as clear imagery as we got.”

The new approach peered inside the hailstones by using computed tomography (CT) scans and reviewing the resulting images. Doing so revealed that even perfectly spherical hailstones have irregular layers of development internally, with their core, known as the embryo, rarely sitting in the center.

“CT scans provide information related to the density, which allows us to identify the different stones’ layers associated with the growth stages of the hailstorm,” added co-author Professor Javier Martin-Vide, a researcher at the University of Barcelona. “They also help us understand the processes that contributed to its formation.”

The non-invasive approach is a first for science, and may help us to predict when deadly storms like the one that rocked the Iberian Peninsula in 2022 are coming.

“We show that the CT scanning technique enables the observation of the internal structure of the hailstones without breaking the samples,” concluded lead author Carme Farnell Barqué, a researcher at the Meteorological Service of Catalonia. “It is the first time that we have a direct observation of the entire internal structure of hailstones, which can provide clues to improve hail formation forecasting.”

The study is published in Frontiers in Environmental Science.