Midwest’s Giant Hailstones: How Did They Form?

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Violent thunderstorms across Nebraska and Iowa this week generated 80-to-100 mile-per-hour winds. But the really scary part for Midwesterners was being pelted with wind-propelled giant hailstones, which in some locations were as big as baseballs.

The meteorological fusillade smashed the windows of buildings and homes, tore holes in roofs and battered cars so badly that some had to be totaled, the Lincoln Journal Star reported.

“Basically, anything on the north side of a house or business is gone," explained Wilber, Neb. resident Scott Hayek.

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It wasn’t just buildings and cars that were damaged. In Friend, Neb., a farmer named Scott Spohn told TV station KLKN that his fields full of corn plants were shredded to pieces by the massive hail, destroying the entire crop.

The video above shows how bad it got in the town of Norfolk, Neb.

So where did these icy projectiles come from, and why did they get so big? According to the National Oceanographic and Atmospheric Administration, hail forms when the updrafts inside a thunderstorm pick up water droplets and carry them into extremely cold areas of the atmosphere, where they freeze into ice.

The late science writer Barbara Tufty wrote that the size to which hailstones grow is determined largely by the speed and strength of the updrafts. The longer that they keep the icy pellets suspended in the clouds, the larger they tend to grow.

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For those fascinated with hailstones, there’s a website, Hail.org, which dutifully records the number and location of hailstorms across the nation each day, and even tracks the reported size of the hailstones. The National Weather Service also offers a handy chart showing what objects compare to hailstones of various diameters.

A hailstone only a quarter of an inch in diameter is pea-sized, for example, while a baseball-sized hailstone is 2.75 inches, and a specimen that’s 4 inches in diameter is classified as grapefruit-sized.

The biggest hailstone ever recorded fell in Vivian, S.D. in July 2010. At 18.62 inches around, it was roughly the size of a volleyball, and weighed one pound, 15 ounces.