A tornado damaged multiple homes, an RV and grain bins on July 18, 2022 / Photo: CHAT News Today

By Meghan Cobb

‘A long, narrow path and evidence of rotation’: tornado and downburst to blame for storm damage

Jul 25, 2022 | 4:17 PM

MEDICINE HAT, AB – Environment and Climate Change Canada has confirmed a tornado touched down in Cypress County, followed by a downburst in Redcliff causing significant damage on July 18.

A team from Northern Tornadoes Project came to Cypress County to gather data and analyze the damage to figure out what actually occurred.

“It wasn’t clear what caused the damage initially,” said Dr. Dave Sills, executive director of Northern Tornadoes Project. “The critical piece of information it turned out, was to get an aerial drone image for the damaged areas to be able to look at it in real detail.”

The team programmed a drone to gather images from a grid pattern allowing for a high-resolution view of the damaged areas. The data from the image produced made it clear a tornado had touched down 10 km south of Redcliff before the storm changed.

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“We could really pick out that it was a tornado that caused the damage in the Cypress County area, but it was a downburst that caused the damage in Redcliff,” Dr. Sills said. “The storm had transitioned from a tornadic storm to a storm that produced a downburst later on.”

Analysts expect to see a long, narrow path of damage from a tornado, sometimes being able to see evidence of rotation in the damage. Damage from a downburst is lighter and more spread out.

“With our drone footage we could see both a long narrow path, and evidence of rotation,” said Dr. Sills. “You could see some of the debris, big pieces of farm equipment and that kind of thing were dragged in a circular motion. It was very clear there was rotational motion around that part of the storm.”

Dr. Sills says it is not uncommon to see storms change from tornadoes to downbursts. Intense updrafts and intense downdrafts rotate around each other, with the updraft causing the tornado to develop. The downdraft winds cause the downburst – a downward and outward wind – which can also cause damage.

The tornado has a preliminary rating of EF-2 with 190 km/h winds, while the downburst is rated as EF-1 with 150 km/h winds.

“There’s a whole list of damage indicators that corresponds to degrees of wind speed,” Dr. Sills explained. “Once you have that wind speed value, then we look at our ranges of EF-1, Ef-2, and so on, and where they fit in there, and then say ‘okay, that was an EF-2 tornado’.”

Dr. Sills says while the ratings are preliminary, it is unlikely they will change. The final assessment comes later on once there is no more data coming in for the analysis.

Dr. Sills says the organization does rely on photos and videos from the public during its investigations, encouraging anyone with footage of the weather event to send it to storm@ec.gc.ca.

So far nothing has been submitted with an image of the actual tornado.

“That’s not uncommon,” said Dr. Sills. “There are a lot of tornadoes that occur that end up being wrapped by rain and then it’s impossible to see them as it’s occurring.”

Data collected by Northern Tornadoes Project for all of its investigations is available to the public through its website.