A Canadian record-breaking hailstone was recovered by Western University's Northern Hail Project (NHP) field team, following a storm earlier this week near Markerville, Alta. The record-breaker weighs 292.71 grams, eclipsing the previous title holder - a hailstone weighing 290 grams, collected nearly 50 years ago in Cedoux, Sask. on July 31, 1973.
With a diameter of 123 millimetres, the hailstone has a slightly larger span than a standard DVD (120 mm).
Led by Francis Lavigne-Theriault, the NHP field team followed a storm to Markerville (about 35 kilometers southwest of Red Deer, Alta.) and found several baseball-sized hailstones.
The team traveled farther south and approximately 20 minutes after the storm had passed (6:14 pm MDT) and recovered several larger hailstones under a tree canopy, many of which are grapefruit to softball-size including the record breaker.
Francis Lavigne-Theriault
Lavigne-Theriault and the team ultimately collected seven bags at the aforementioned location, all of which are baseball-sized hail or larger (at least 70 millimetres or 2.75 inches in diameter). The samples are currently being stored in a freezer.
"It wasn't until I returned and started sifting through the bags that I found the record-breaking stone," said Lavigne-Theriault. "It was bagged with other stones without realizing what we had in our possession!"
NHP executive director Julian Brimelow and some of his severe weather colleagues from around the world maintain a database of record hailstones. Currently, only 22 hailstones, including the Markerville one, have weighed more than 290 grams.
Julian Brimelow
"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."
Because giant hailstones are so rare, the international research community does not have a good understanding yet of what conditions are required for hailstorms to produce them.
"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 researchers can also use ice from the different layers for chemical and isotope analyses to also help them understand the hailstone's journey through the storm.
3D scans of the stone can also be used to make silicon moulds or 3D prints that the NHP team can use to make ice replicas for conducting experiments to study fall behaviour and aerodynamics of these giant hailstones.
"By any measure, Monday's storm was remarkable," said Brimelow. "If you were to ask experts where in Canada a new record largest hailstone would be found, they would probably say Saskatchewan. We were expecting significant severe hail in Alberta on Monday, but not a new national record."
The previous Alta. record hailstone fell during the Edmonton tornado on July 31, 1987. That stone weighed 264 grams with a diameter of 104 millimetres.
For comparison, the current record holder for the largest hailstone in North America is a stone that fell near Vivian, South Dakota on July 23, 2010. That stone weighed 879 grams and had a maximum diameter of 203 millimetres.
NHP is a research spinoff of the Northern Tornadoes Project, which was founded in 2017 as a partnership between Western University and ImpactWX.
This is the first-year of NHP, a five-year Western-led project based in Red Deer, Alta.
