The remaining foundation of a destroyed home in Sainte-Anne-du-Lac observed after a tornado on June 18, 2017. Photo courtesy of

Historic Tornado Find By Western Researchers

Tornadoes that tore up southern Québec last summer have been identified as one of the largest twister outbreak in Canadian history, thanks to the work of researchers at Western University.

Western wind engineering experts conducted an extensive ground and aerial survey following the June 18, 2017 touchdown of a cluster of tornadoes to a region, spanning more than 400 km. The supercell thunderstorms developed in southern Québec producing large hail, high winds, and damaging tornadoes.

Initially, it was believed a total of four tornadoes formed that day, but new data from Western identified seven additional twisters. The finding makes it the largest tornado outbreak in the province’s history and one of the latest ever recorded in Canada.

“Many Canadians don’t realize that we can have intense tornadoes in the northern regions of the country. The goal of our project is to identify as many of these as we can, so that we can better define the true risk in those areas,” said Greg Kopp, a Western engineering professor and the lead researcher.

Using advanced satellite imagery, researchers studied the targeted tornado region to isolate any previously unknown damage including significant tree falls in remote and heavily forested areas that are often difficult to reach on foot. The high-resolution aerial images were taken by aircraft flying over Sainte-Anne-du-Lac, Lac Noir, Lac des Cornes, Hébertville, and Lac de la Boiteuse last July. A second aerial survey was ordered over Sainte-Anne-du-Lac in January after researchers discovered the entire tracks of the storms were not captured the during the first fly-over.

Significant damage was also found to residential buildings in Sainte-Anne-du-Lac and Hébertville during ground surveys done by Western and the Quebec Storm Prediction Centre.

The strongest tornado of the day was an EF-3 in Sainte-Anne-du-Lac. It tracked 30.5 km and was 1,300 metres wide. The Hébertville tornado was rated as an EF-2, with a track length of 22.5 km and was 900 metres wide.

The project also identified two previously undetected tornadoes in northern Ontario. Both tornadoes formed in the Dryden area, one on June 14, 2017 and the other on July 25, 2017.

The survey was conducted by Kopp, Joanne Kennell, and Emilio Hong from Western’s Department of Civil and Environmental Engineering and David Sills from Environment and Climate Change Canada.