Researchers investigating a 2018 hail storm have found one hailstone likely measured between 7.4 and 9.3 inches across, potentially setting a new world record.
The supercell thunderstorm pelted a city center in Argentina with hailstones so large scientists suggested a new category to describe them: gargantuan hail.
The current record belongs to a hailstone that measured 8 inches across, or about the size of a volleyball, that fell near Vivian, South Dakota.
“It’s incredible,” says Matthew Kumjian, associate professor in the meteorology and atmosphere science department at Penn State. “This is the extreme upper end of what you’d expect from hail.”
The scientists propose hail larger than 6 inches should get “gargantuan” classification, and say more awareness of these events, while rare, could help piece together a better understanding of the dangerous storms.
“Anything larger than about a quarter in size can start putting dents into your car,” Kumjian says. “In some rare cases, 6-inch hail has actually gone through roofs and multiple floors in houses. We’d like to help mitigate the impacts on life and property, to help anticipate these kinds of events.”
Gargantuan hail on social media
The storm in heavily populated Villa Carlos Paz, Argentina offered scientists a rare opportunity to study a well-documented case of gargantuan hail. As the storm unfolded, residents took to social media, posting pictures and videos.
Researchers followed up on the accounts a year later, interviewing witnesses, visiting sites where damage occurred, collecting photogrammetric data, and analyzing radar observations. Using photogrammetry—taking measurements from photographs—and video evidence, the scientists estimated one hailstone may have set a world record.
“Such a well-observed case is an important step forward in understanding environments and storms that produce gargantuan hail, and ultimately how to anticipate and detect such extreme events,” Kumjian says.
Hail typically occurs during severe storms, which produce strong, sustained updrafts. The winds hold hailstones aloft long enough to grow in sub-zero temperatures high in the atmosphere. But predicting hail size remains challenging, scientists say.
‘Crazy, high-impact events’
Graduate student Rachel Gutierrez, a coauthor of the paper, found a connection between a storm updraft’s rotational velocity, or how fast it is spinning, and larger hail size, but much remains unknown about the relationship.
The data, especially from a storm outside the United States, is invaluable, she says.
“There typically isn’t a lot of data from storms outside the US. Having this shows us these crazy, high-impact events can happen all over the world,” Gutierrez says.
Gargantuan hail events may be more common than once believed, but researchers need volunteers willing to report hail and provide accurate measurements, either by including a common item for scale, or a ruler, Gutierrez says.
The findings appear in the Bulletin of the American Meteorological Society.
Additional researchers are from the Bureau of Meteorology in Australia, the University of Illinois at Urbana-Champaign, the National Center for Atmospheric Research, the Pacific Northwest National Laboratory, the Centro de Investigaciones del Mar y la Atmósfera in Argentina, and Penn State. The National Science Foundation and the Insurance Institute for Business and Home Safety partly funded the work.
Source: Penn State