"Gorilla Hail" Has Been Pounding The U.S. This Year, And It's Likely More Common Than Previously Thought

Giant hail in Wisconsin this past April.

It's been another rough year for hail storms in the United States. There's been lots of them and a few of them have been real standouts. 

Probably the most newsworthy and perhaps most extreme was the one that hit Springfield, Missouri and nearby areas on April 28. 

Baseball to softball sized hail laid wasted to probably thousands of cars. Sadly, an emu died from the hail at Dickerson Park Zoo in Springfield. Zoo workers tried their damndest to get all the zoo animals under cover. 

An emu's natural instinct is to lie down and take cover, and this emu, a 21 year old female named Adam, couldn't be coaxed indoors and died when a huge hailstone landed on his head. 

Back on March 10, a supercell that produced a destructive tornado in Kankakee, Illinois also produced immense hail that might have broken the record for the largest hailstone in Illinois history. It measured 6.616 inches in diameter and weighed 1.22 pounds. In other words, it was a little larger than a grapefruit. 

Officials are verifying those measurements before declaring it a record holder. In any event huge hailstones damaged homes in Kankakee that were never touched by the tornado.

The tornado, with maximum winds of 150 people killed three people. 

Even here in Vermont, we managed to see some rare or us golf ball sized hail on April 16 when a supercell thunderstorm crossed west to east across central Vermont. The supercell is the one that ultimately produced a brief tornado in Williamstown. 

GORILLA HAIL

Reed Timmer, one of the more popular and prolific storm chasers out there, coined the term "gorilla hail" to describe especially ferocious hailstorms with especially huge hailstones. 

Gorilla hail is generally defined as hailstones with a diameter of at least two inches, which is about the size of a lime.

Big hailstones are expensive. Replacing a hail-damaged roof can cost $15,000 or more, though homeowners;' insurance usually covers that. (On that note, a spoiler:  Look for an upcoming piece on how State Farm is allegedly doing everything they can to not pay for hail damaged roofs).

Fixing a hail-damaged vehicle can cost several thousand dollars, but if the damage is severe enough, insurers will just total the car.  

Hail costs an estimated $15 billion in damage to homes, buildings, vehicles and crops each year in the U.S. 

Hail-prone cities and their surrounding suburbs continue to expand, providing more targets for potential gorilla hail. That's helping to cause hail costs to spiral upward. 

NOT SO RARE?

It seemed fortunate that "gorilla hail," with stones the size of baseballs, softballs, grapefruit or even worse, was considered relatively rare. But maybe not. 

New research in recent years suggest "gorilla hail" has always been more common than we thought. And super giant hail might be becoming more frequent. 

It was thought that hail stones six inches in diameter or greater were exceedingly rare. But new research suggests maybe those gargantuan icy meteors aren't quite as rare as we thought.  

Per Washington Post:

"'I think six inches plus is happening on a yearly basis,' said Victor Gensini, a professor at Northern Illinois University, in a recent interview. "I think it's a matter of who's finding it, who's looking for it. When you're actually out there looking for it, four-plus-inch hail is maybe not that rare."

Most of these giant hailstones are happening in fairly remote areas, where people aren't around to observe them before they melt. Or, since such large hail is so dangerous, and maybe accompanied by ferocious, damaging winds or even tornadoes, people who would otherwise find them are wisely hunkering down in basements and storm shelters.

Besides, most big hail stones shatter upon impact. To find these hail stones, you need a road that happens to lead where the biggest hail stones landed, Gensini said. Most hail falls over open fields. Good luck finding the biggest stones before they start to melt. 

Thunderstorms that produce gargantuan hail can't actually have too much water in therm. Storms with incredible amounts of rain tend not to produce the biggest hail. Bigger hail also seems to fall when a small storm merges with a large supercell that is already producing hail.

The bad news from all this research is that future storms might produce bigger hail, thanks, once again, to climate change. 

The Washington Post tells us:

"Gensini published a paper in 2024 that suggests less hail will occur overall, ut there will be more instances of giant hail. Why? Warming temperatures in the lower atmosphere will melt some of the small hailstones. Yet big stones fall fast enough through the warmer lower atmosphere that they have little time to melt. And with more thunderstorm fuel overall thanks to a warming world, there could be more of them."

We will probably get more and more new reports of giant hail simply from better technology. At least 90 percent of hailstones shatter or break on impact, and the rest start to melt immediately.  

Researchers are starting to use photogrammetry, a technique that uses trigonometry to estimate the sizeof objects caught on camera. (And you thought there was no use for trigonometry when you were back in high school!)

A hail specialist at Penn State used the technique to estimate the size of a gorilla hailstone that fell on an Argentinian with in 2018.  He found the hailstone to be 7.4 to 9.3 inches in diameter. A woman found a 7.1 inch diameter hailstone just after the storm ended, collaborating the photogrammetry. The woman's hailstone was a bit smaller as it had already started to melt.

Gorilla hail is terrifying and incredibly destructive. You don't want to get caught in any of these storm. Here's hoping you don't experience one of those storms!