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The Hunt for Big 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 some bad news. His world record was broken, the clerk told him. That is, 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 had found a bigger one, the clerk said.

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

Fortunately for Mr. Scott, this was not quite right. On August 1, a team of scientists from Western University in London, Ontario, collected a giant hailstone while hunting for a storm in Alberta, about 75 miles (75 km) north of Calgary. The hailstone was two inches in diameter and weighed just over half a pound—half the size and a quarter of Mr. Scott’s weight. So it was not a world record, but a Canadian one.

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

But the record-setting has come with increased hail damage. While the frequency of reported “hail events” in the United States is the lowest in a decade, according to a recent report by Verisk, a risk assessment firm, insurance claims on cars, homes and crops damaged by hail reached $16.5 billion in 2021 — the highest ever. Hail can strip plants down to the stem and basically make small cars total. Ten years after the record storm in Vivian, the tin roofs of some buildings are still dented. Hail storm on Wednesday killed a toddler in the Catalonia region of Spain.

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

While changing climate likely plays a role in these trends, weather experts say, a more complete explanation could have something to do with the self-generating interplay of human behavior and scientific discoveries. As neighborhoods extend into areas of heavy hail and greater hail damage, researchers have tracked down large hailstones and documented their sizes, sparking public interest and prompting further investigation.

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

The big-hail fixation dates back to at least 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 in crop damage per year.

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

It didn’t. And a decade of research demonstrated that the Soviet effort probably hadn’t worked either. Both countries eventually gave up on the idea and hailstone investigations ground to a halt, though cloud seed increased rain and snowfall continued – and continues to this day – all over the world.

During that silence, in 1986, a hailstone Reportedly Weighing 1.02 kilograms – about two and a quarter pounds, the heaviest ever recorded – was collected in Gopalganj, Bangladesh, during a storm that killed 92 people. All data on the hailstone – with the exception of eyewitness accounts and the claimed weight – was lost. The Gopalganj stone became something of a fable among hail researchers, with a moral attached to it: there were large hailstones, but documentation was vital.

This prompted Kiel Ortega, a meteorologist who started hail research in 2004, to call too cold. Using Google Earth, he found businesses in the path of storms and called them for on-site updates. “As much as I like to chase storms,” ​​he said, “at some point you don’t have enough money or people to keep going out.”

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 undergraduate students to compile reports when a severe hailstorm formed in the United States. How big was the “hail track” – 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 their family or friends. Third? Put it in the freezer – where sublimation, the phase change from solid ice to water vapor, can 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 by about two inches, he said. “I just didn’t realize what I had,” he said. “Many more hailstones fell, and there were bigger ones than the ones I picked up.”

Each hailstone has a story cryptically etched into its shape and layers. To decipher the story, 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 those models and piece together a stone path from the storm to the ground.

But some of the most basic features of great hail remain shrouded in mystery; research 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 in the world.”

Almost all hail is created in supercells, or storms with ascending air currents that rotate slowly. Tiny bits of ice called embryos get swept up in that updraft like “a fountain of particles,” says Matt Kumjian, a meteorologist at Penn State University who studies the internal dynamics of storms. The embryos fall into water droplets and become hailstones that continue to grow until they are too heavy to linger and then fall to the ground.

In recent years, Dr. Giammanco and his colleagues have been traveling across North America to create 3D scans of large hailstones. Later in the lab, using “probably the most advanced ice machine in the world,” said Dr. Giammanco, the team recreates the hailstones to calculate their fall speed and the damage they can cause.

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

Every detail is a clue. A cloudy hailstone layer indicates that the water immediately froze on the embryo, trapping air bubbles in it. Clear ice means the water had time to expand around the embryo before it froze. Spherical hailstones are thought to have tumbled into the supercell; spiky shoot like comets through the storm.

The end of a hailstone story often draws public attention. If some ice breaks your windshield, do you really care which path it took through a supercell? But, said Dr. Kumjian, tracing the ontogeny of hail could help scientists better predict where and when large hailstones will fall.

Canada’s record 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 about 20 minutes after the hail trail passed to a stretch of road. The ground was littered with baseball-sized hailstones, the largest of which the researchers put in a bag and froze.

The largest hailstones “are actually more of academic interest,” said Dr. Brimelow, because they “fall in such low concentrations that they are not really as dangerous as golf ball-sized hail.” But, said Dr. Kumjian, looking for “the absolute worst-case scenario” can refine prediction models and help explain the dynamics of supercells. Studying single hailstones over time can have too great an effect on understanding storms. And, he said, there is the irresistible question: what is the limit of nature?

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

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

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

When Mr. Scott learned that his world record hadn’t been broken after all, and heard exactly what had happened—the crossed wires, the multiple records, the grams and the pounds—he was relieved. His birthday was not ruined; he was able to tell his friends and family that his record remained intact.

He grinned, then said, “I’ll get a pat on the back.”