Central Alberta has become a focal point for unusually violent convective storms this summer, with residents and researchers alike examining why so many powerful cells have formed across the region.
Supercells, long residence time and big hail
Last weekend a supercell near Edmonton produced hailstones described as roughly the size of tennis balls and left vehicles with shattered windshields. Photographs and video shared by a Parkland County resident place that event roughly 50 kilometres west of Edmonton on July 25. The images show hail with layered, lobate structure — an indication the stones spent extended time cycling through the storm’s core.
Researchers point to the structure and strength of supercells as key to producing unusually large hail. Simon Eng, a research meteorologist with the Northern Hail Project at Western University’s Canadian Severe Storms Laboratory, explains that hail growth depends on how long ice particles remain suspended in cold upper-level updrafts.
“Looking at things that maximize residence time, they include how wide the updraft is. And when you have a supercell, you’ve also got rotation, so while hailstones are rising, they’re rotating around like a merry‑go‑round.”
Storm counts and intensity: a striking summer
So far this season Alberta has seen a notable spike in tornadic activity. The province has recorded 27 tornadoes this summer — more than twice the long‑term figure of 11.2 per year. The Prairies have also experienced an unusually high number of severe tornadoes, with three EF‑3 events reported compared with the typical expectation of one.
| Indicator | This summer (Alberta) | Long‑term/typical |
|---|---|---|
| Number of tornadoes | 27 | 11.2 |
| EF‑3 tornadoes | 3 | 1 |
Why Alberta?
Experts say several pieces must line up to create such extreme storms. A broad and vigorous updraft increases the time ice particles spend in supercooled regions, allowing hail to accumulate layers and reach large sizes. Rotation within a supercell helps keep hailstones aloft longer, further lengthening their growth period.
Localised conditions can make the difference between a routine thunderstorm and one that produces destructive hail or a tornado. That explains why massive hail and tornadic activity remain spatially limited even within a generally stormy period, yet can cause disproportionate damage where they hit.
- Supercell structure: rotation and wide updrafts favour long hail residence time.
- Local dynamics: even brief, isolated cores can create very large hail if conditions align.
- Seasonal anomaly: Alberta’s tornado count and number of intense tornadoes are well above typical figures.
Although the most recent hail episode was relatively isolated in space and time, the force of falling stones was sufficient to cause vehicle and property damage. The Northern Hail Project’s sampling and analysis of these events will continue to inform understanding of how convective storms in the Canadian Prairies are changing in frequency and intensity.
For residents, the results underline the importance of heeding severe‑weather warnings, securing vehicles and property where possible, and maintaining awareness during summer storm setups that can evolve rapidly into destructive supercells.
As investigators catalogue damage and analyse storm structure, meteorologists caution that isolated but intense events can strain emergency services, insurers and communities — even when the larger region receives only brief, scattered impacts.
The combination of photographic evidence, lab analysis and ongoing field research by groups such as Western University’s lab and the Northern Hail Project will be central to refining forecasts, warnings and resilience strategies for future severe‑weather seasons.
