© Francis Lavigne-Theriault/Northern Hail ProjectThis record-breaking hailstone was recovered northwest of Markerville, Alta., on Monday. Its weight was recorded as 292.71 grams and its diameter as 123 millimetres.
The record breaker was found under a tree canopy near Markerville, about 110 kilometres north of Calgary, shortly after the storm had passed, with several other grapefruit- to softball-sized hailstones.
The previous Canadian record holder, collected on July 31, 1973, in Cedoux, Sask., weighed 290 grams and was 114 millimetres in diameter, said the research group based in Alberta.
"It wasn't until I returned and started sifting through the bags that I found the record-breaking stone," said Francis Lavigne-Theriault, part of the group's field team, in a news release.
"It was bagged with other stones without realizing what we had in our possession."
Julian Brimelow, executive director of the Northern Hail Project, said his severe weather colleagues from around the world maintain a database of record hailstones. Only 22 hailstones, including this one, have weighed more than 290 grams.
"Finding large hailstones like this is like hitting the jackpot. So this Markerville sample joins an elite club of giant hailstones," said Brimelow.
"This stone will also help us refine our estimate of just how large it is possible for hail to grow."
The current record holder for the largest hailstone in North America fell near Vivian, South Dakota, on July 23, 2010. It weighed 879 grams and had a maximum diameter of 203 millimetres.
'It was extremely intense'
Although the discovery is exciting, Monday's storm was quite terrifying for drivers along the Queen Elizabeth II Highway between Innisfail and Red Deer.
Matt Berry got on the road at about 6 p.m. that day, and said it was "perfect" weather.
But about 10 minutes later, the storm rolled through the area, hurling massive chunks of hail down on dozens of cars on Antler Hill.
© Matt BerryLarge hailstones fell near Innisfail, Alta., and damaged dozens of vehicles shortly after 6 p.m. Monday.
"My windshield is absolutely destroyed.... I was just scared of this thing coming in on top of me."
He managed to pull off to the side of the road and waited for the storm to pass. In all, it lasted for 10 to 15 minutes, he said.
According to RCMP, 34 vehicles were damaged Monday — down from an earlier estimate of 70 — while numerous people suffered minor injuries. Three collisions were caused by the storm, police said.
Stuart Brideaux, public education officer with Alberta Health Services, said local fire and EMS also attended the scene, arriving at about 6:30 p.m.
Although some people were hit indirectly by hail coming through windows and broken glass, he said no one required transportation to the hospital.
It's good news, considering the size of the hailstones coming down. Brimelaw said the intensity of the storm was a surprise even to his team.
"We were getting reports of grapefruit-sized hail, softball-sized hail.... Usually in an exceptional day, we maybe have tennis ball-sized hail, so six to seven centimetres. But [Monday], we had a lot of stones that were over 10 centimetres across," he said.
The Northern Hail Project team said it worked independently to confirm the record.
On Wednesday, Environment Canada said that softball-sized (10.6 cm) hail was recorded in Markerville, baseball-sized (7.5 cm) hail fell in Innisfail and Milnerton, and tennis-ball sized (6.4 cm) hail hit Sylvan Lake, Penhold and Wimborne, Alta.
Brimelow said he's not sure why the hail in this storm was so much bigger than usual, but he expects it may have something to do with an abundant amount of moisture near the ground Monday, which isn't typical in Alberta.
That element, along with the usual storm ingredients, may have come together to give more fuel to the creation of the hailstones.
"Every new data point helps inform us on what conditions are required," said Brimelow.
"Once we have measured and 3D scanned the Markerville hailstone, we can then make thin sections. The growth layers evident in those will reveal information on the hailstone's growth history in the storm."
The team may also use 3D scans to study fall behaviour and the aerodynamics of large hailstones.
Matt Melnyk, a storm chaser in Alberta, also wonders what led to the hailstones' size. He went to Innisfail Monday to assess and take photos of the storm.
"This particular storm had a very, very large rotating updraft, which kept the hail inside the storm for a long period of time," he said in an interview with CBC Calgary News at 6.
"It was extremely intense."
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