Photos From Twitter/David Hart via Nathan Howes TWN

By Chris Brown

Canada Day tornado in Alberta rated an EF4

Jul 4, 2023 | 10:34 AM

A team of experts has classified the tornado that tore through south central Alberta on Canada Day as an EF-4. It’s the strongest tornado to hit the province in more than 35 years.

The damage survey was conducted by Environment and Climate Change Canada in collaboration with the Northern Tornadoes Project. They say winds reached an estimated 275 km/h.

The tornado developed near Sundre, moving southeast to the Didsbury and Carstairs area. The heaviest damage was reported where the tornado crossed Highway 2A between those two communities, weakening and dissipating near the QEII Highway.

“This tornado caused damage to 12 homes, of which 3 were completely destroyed and 4 were left uninhabitable,” reads the report from ECCC. “The most notable damage occurred at the farm on the west side of Highway 2A. A well-constructed home was destroyed in this location with all exterior and above-grade interior walls knocked down. The homeowner was in the house at the time and took shelter in the basement.”

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The ECCC says all homeowners its representatives spoke to received the tornado warning notification on their mobile devices and reacted accordingly, either seeking shelter in their basements or leaving the area.

The report says the tornado’s path length was 15.3 km with a maximum path width of 620 m. It estimates the tornado lasted for 30 minutes.

The last time there was an F/EF4 tornado was in Edmonton on July 1, 1987.

The EF (Enhanced Fujita) Scale is a six-point scale that ranges from zero, the weakest, to five, the strongest. It’s been used since April 2013, deemed to be an improved and more modern version of the original Fujita Scale or F Scale.

Table 1. Comparison of F-Scale and EF-Scale wind speeds (adapted for Environment Canada) associated with damage ratings. Note that for the EF-Scale wind speeds have been increased for lower ratings and decreased for higher ratings. (Image From Environment and Climate Change Canada)

Anyone with information about the tornado or to report severe weather at any time is asked to call 1-800-239-0484, email abstorm@ec.gc.ca or tweet to #abstorm.