The Hunt for Large Hail

In August, a few days before his 68th birthday, Leslie Scott, a rancher in Vivian, SD, went to the post office where he received bad news. The clerk told him his world record had been broken. That said, the hailstone Mr. Scott collected in 2010, which measured eight inches in diameter and weighed nearly two pounds, was no longer the largest on record. Some people in Canada would have found a larger one, the clerk said.

“I’ve been sad all weekend,” Mr. Scott said a few days after hearing the news. “I told everyone my record was broken.”

Fortunately for Mr. Scott, that wasn’t quite right. On August 1, a team of scientists from Western University in London, Ontario collected a giant hailstone as it chased a storm in Alberta, about 75 miles north of Calgary. The hailstone was five inches in diameter and weighed just over half a pound – half the size and a quarter the weight of Mr. Scott’s. So it wasn’t a world record, it was a Canadian one.

The Canadian hailstone was added to the list of regional records set in recent years, including Alabama in 2018 (5.38 inches long, 0.612 pounds), Colorado in 2019 (4.83 inches, 0.53 pounds) and Africa in 2020 (about seven inches long). , weight unknown). Australia set a national record in 2020 and set it again in 2021. Texas’ record was set in 2021. In 2018, a storm in Argentina produced rocks so large that it introduced a new class of hail: giant hail. Bigger than a honeydew melon.

But the record has been accompanied by increased hail damage. Despite the frequency of reported “hail events” in the United States at its lowest level in a decade, insurance claims for hail-damaged cars, homes and crops hit $16.5 billion in 2021, according to a recent report by Verisk, a risk assessment firm. Dollar – the highest ever. Hail can uproot plants and effectively damage small cars. Ten years after the record storm in Vivian, the tin roofs of some buildings are still dented. On Wednesday, a hailstorm killed a toddler in Spain’s Catalonia region.

“It’s one of the few weather hazards that we don’t necessarily build for,” says Ian Giammanco, meteorologist at the Insurance Institute for Business & Home Safety. “And it just keeps getting bigger and worse.”

Though climate change likely plays a role in these trends, a more complete explanation may have something to do with the self-fueling interplay of human behavior and scientific discoveries, weather experts say. As neighborhoods spread into areas experiencing severe hail and greater hail damage, researchers have sought out large hailstones and documented their extent, raising public interest and stimulating further study.

Julian Brimelow, the director of the Northern Hail Project, a new collaboration of Canadian hail research organizations whose team found the record-breaking hailstone in August, said: “It’s quite an exciting time to be doing hail research.”

The fixation on large hail dates back at least to the 1960s, when Soviet scientists claimed they could significantly reduce the size of a storm’s hailstones by dispersing chemicals into the atmosphere. The method, called cloud seeding, promised to save millions of dollars a year in crop damage.

In the 1970s, the United States funded the National Hail Research Experiment to replicate the results of the Soviet experiments, this time using cloud formation in hailstorms over northern Colorado. Scientists then collected the largest hailstones they could find to see if it worked.

It has not. And a decade of research showed that the Soviet effort probably didn’t work either. Both countries eventually abandoned the idea, and hailstone research stalled, although seeding of clouds to increase rain and snowfall continued — and continues to this day around the world.

During that hiatus in 1986, a hailstone weighing 1.02 kilograms – about two and a half pounds, the heaviest on record – was collected in Gopalganj, Bangladesh, during a storm that killed 92 people. All records of the hailstone – except eyewitness accounts and its alleged weight – were lost. The Gopalganj Stone became something of a fable among hail researchers with a moral: there were large hailstones, but documentation was vital.

This prompted Kiel Ortega, a meteorologist who began hail research in 2004, to start cold calling. Using Google Earth, he found companies sitting in the paths of storms and called them for up-to-date information on the spot. “As much as I like chasing storms,” ​​he said, “at some point you won’t have enough money or people to go any further.”

Weather models indicated where hail might form and what the average size of the hailstones might be, but their predictions were often far off. So, Mr. Ortega assembled a team of researchers and students to cobble together reports whenever a severe hailstorm formed in the United States. How big was the “hail swath” – the area of ​​the storm that dropped hail? How big was the largest hailstone?

Most reports of record hail are made by civilians, but accuracy is often lacking. The first thing most people do when they find a large hailstone? Take a picture. Second? Show it to your family or friends. Third? Put it in the freezer – where sublimation, the phase change from solid ice to water vapor, will shrink the hailstone over time.

Mr. Scott in Vivian kept his world record in the freezer for weeks before anyone from the National Weather Service could officially measure and weigh it. During that time, it shrank about three inches, he said. “I just didn’t know what I had,” he said. “A lot more hailstones fell, and there were bigger ones than what I picked up.”

Each hailstone has a story cryptically engraved into its shape and layers. To unravel history, scientists use mathematical models to predict where hail will fall and what it will look like; They then collect and analyze real hailstones to refine these models and piece together a stone path from storm to ground.

But some of the most basic features of the great hail remain obscure; Collection procedures are inconsistent and funding is scarce. How fast do these hailstones fall? What gives a hailstone its shape? How big can a hailstone get?

“Hail data is terrible,” said Dr. Brimelow. “It’s probably one of the worst data sets on the planet.”

Almost all hail originates in supercells, or storms with updrafts of slowly rotating rising air. Small pieces of ice called embryos are swept along in these updrafts like “a fountain of particles,” said Matt Kumjian, a Penn State meteorologist who studies the inner dynamics of storms. The embryos smash into droplets of water and become hailstones, which continue to grow until they are too heavy to stay airborne, and then fall to the ground.

In recent years, dr. Giammanco and his colleagues traveled across North America taking 3-D scans of large hailstones. Later in the lab, the team with “probably the most advanced ice machine in the world,” said Dr. Giammanco followed the hailstones to calculate their falling speed and the damage they could cause.

Mr. Ortega and his colleagues have used high-speed photography to capture large hailstones in motion. This involves sprinting in front of supercells and setting up camera systems to better understand how fast the ice is moving when it hits the ground and what shape it takes just before impact.

Every detail is a clue. A cloudy layer of hailstones indicates that the water immediately frozen on the embryo, trapping air bubbles inside. Clear ice means the water has had time to expand around the embryo before it freezes. Spherical hailstones are said to have swirled around in the supercell; Spiky shoot like comets through the storm.

The end of a hailstone’s story is often what captures the public’s attention. When ice cracks your windshield, do you really care which way it took through a supercell? But, said Dr. Kumjian, tracing hail ontogenesis can help scientists better predict where and when large hailstones will fall next.

Canada’s record-breaking hailstone was collected when the Northern Hail Project intercepted a supercell as it passed through central Alberta. The researchers used radar forecasts to predict the storm’s path, then stopped at a stretch of road about 20 minutes after the hailstorm passed. The ground was littered with baseball-sized hailstones, the researchers bagged and frozen the largest of them.

The largest hailstones “are really more of academic interest,” said Dr. Brimelow because they “fall in such small concentrations that they are not really as dangerous as golf ball-sized hail”. But, said Dr. Kumjian, the search for “the absolute worst-case scenario” can refine forecasting models and help explain the dynamics of supercells. Studying individual hailstones over time can have a tremendous impact on understanding storms. And, he said, there is the irresistible question: What is nature’s limit?

dr Kumjian and Dr. Brimelow have compiled a database of the largest hailstones recorded in the world. The two believe they have determined the maximum possible size of the hail: just over three pounds and about a foot in diameter. They will present their findings in September at the second North American Hail Research Workshop in Boulder, Colorado.

Francis Lavigne-Theriault, who coordinates storm chasing and field operations for the Northern Hail Project, said the presence of large hail in central Alberta suggests it’s likely to occur “much more frequently” than previously thought. dr Brimelow said the record was “quite remarkable” as hail forming conditions in the area were generally less “juicy” than other areas of the country.

In other words, there are many more records to be found.

When Mr. Scott was informed that his world record had not yet been broken and he was told exactly what had happened – the wires crossed, the multiple records, the grams and the pounds – he was relieved. His birthday wasn’t ruined; he could tell his friends and family that his records remained intact.

He chuckled and then said, “I’m going to get a pat on the back.”

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