30 years since Alberta's deadliest tornado

Monday, July 31, 2017, 12:38 PM - July 31, 2017, marks 30 years since a powerful tornado tore a path of destruction through one of Canada's largest cities.

The Edmonton Tornado, also called the Black Friday Tornado, was one of the most powerful twisters to ever touch down in Canada, boasting winds up to 420 km/h, or F4 strength. It was on the ground for about an hour, as it ripped through Strathcona County and the eastern part of the city, leaving a damage path 40 km long and up to a kilometre wide in places.

The death toll was enormous by Canadian standards. 27 people lost their lives due to the twister, with hundreds more injured. That made the Edmonton Tornado the second-deadliest in Canadian history, behind only the so-called Regina Cyclone of June 30, 1912, which killed 28 people.

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Environment Canada says around 300 homes were destroyed, and the total economic cost topped $330 million in damages.

Four other tornadoes touched down in Alberta that day, according to Environment Canada, though none matched the intensity of the one that ripped through Edmonton.

The disaster forced a rethink of public alerting during destructive severe weather events. A lookback by Environment Canada, linked to below, gives a sense of how quickly the situation escalated:

Radar and satellite indicated rapid intensification of the line of thunderstorms as it moved toward Edmonton at 70 km/h (43 mph). A "severe weather warning" was issued at 1445 hours, with as yet no reports of severe events being reported from weather stations or weather watchers. By 1445 hours a new thunderstorm cell developed explosively near Leduc, ahead of the previous line of storms. At 1455 hours a tornado dropped to the ground from this cell briefly and retracted. It struck again near Beaumont as the "Edmonton Tornado" and remained on the ground for an hour over a 40 km (25 mile) path. At 1459 hours, a call reporting a tornado was received, the source being a member of the general public. A tornado warning for Edmonton was issued.

Severe weather alerting has improved considerably Canada-wide since the Edmonton Tornado, as well as the 1985 tornado outbreak in Ontario which killed 12 people. Alberta led the way on revamping alerting systems, establishing the Alberta Emergency Public Warning System soon after.

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