Look Out Below!
Imagine that a chunk of ice the size of a cantaloupe fell on your head. Not a pleasant thought. But hailstones can get that big. In 2018 a hailstone that was probably close to nine inches in diameter landed in the city of Villa Carlos Paz, Argentina. Why “probably”? Well, hail is difficult to measure. It starts melting pretty much as soon as it hits the ground (or your car, or whatever), and bits of it break off when it hits. So determining the size of hailstones takes a bit of sleuthing. After a report of large hail, meteorologists interview witnesses to the hailstorm and examine evidence such as dents in cars, holes in windshields, and, in at least one case, a hole in the roof of a house where a hailstone ripped through.
Documenting the size of hail is easier than it used to be, though. Thanks to social media, most people, armed with cell phone cameras, are eager to snap pictures and record videos of giant hailstones and share them with the world. That happened in Villa Carlos Paz, when a nasty supercell thunderstorm dropped an especially large chunk of hail. A local teenager saw the whopper, took some photos and videos, and posted them on the internet. Then she stashed the stone in the freezer. When scientists from the University of Pennsylvania saw the pics, they rushed down to have a look. In addition to examining the remains of the stone (which had shrunk a bit in the freezer), they used a technique called photogrammetry to calculate the size of the hail based on the photos and videos. It was a real meteorological CSI. And the evidence indicated that when the stone landed, it was at least 7.3 inches and probably closer to nine inches in diameter. A record-breaking chunk of hail.
Photographing hailstones — especially with a ruler in the picture — is a good way to document their size. But taking photos in the middle of a hailstorm is not safe. Hailstones much smaller than the one in Villa Carlos Paz have killed people. It’s best to wait until the storm has passed to take your measurements, even if that means your data won’t be as accurate.
And get this. There’s a technical name for whopper hail stones (those larger than six inches in diameter): Gargantuan. I wonder how big they have to get to be officially designated “ginormous”?
’til next time,
Avery
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