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What’s the likelihood of an EF5 tornado in Canada?


October 10, 2018   by Jason Contant


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Following the EF3 tornado that struck Dunrobin, Ont. on Sept. 21, should insurers worry about the potential for a powerful EF5 strike on a major population centre in Canada?

Probably not. But they should be concerned about tornadic storms in major centres, although not necessarily EF4s or EF5s, said Glenn McGillivray, managing director of the Institute for Catastrophic Loss Reduction (ICLR).

Environment Canada officials inspect the damage in Elie, Manitoba, on Saturday, June 23, 2007 following Friday’s tornado. The tornado destroyed at least four homes and damaged several others, but there were no reports of injuries. (CP PHOTO/John Woods) CANADA

EF4s (wind speeds of 270-310 km/h) and EF5s (wind speeds greater than 315 km/h) are extremely low probability, but high to very high impact events.

The only F5 ever recorded in Canada occurred in Elie, Man. on June 22, 2007. The twister destroyed or damaged several homes, totaled several vehicles, but took no lives. Insured damage came in at about $20.5 million.

“In my view, insurers should be more concerned about a strike from a well-placed lesser tornado which, statistically, is more likely and which could have fairly serious consequences,” McGillivray wrote in a blog published Oct. 2. “Such an event could be of particular concern to a small local/regional writer that may have concentration issues in a given area and a cat reinsurance program that may not be up to the job.”

So, while insurers must always be cognizant of the potential for extremely low probability/high impact events (an EF5 tornado), “they cannot and should not lose site of the fact that a lesser event with a higher probability of occurrence but lower impact could, in some circumstances, be almost as painful.”

What needs to be reinforced, McGillivray said, is that you don’t need an EF4 or EF5 to incur total losses of homes and other structures. As was illustrated in Vaughan, Ont. in Aug. 2009 (where two F2s struck, one in Woodbridge and one in Maple) and Angus, Ont. in June 2014 (also an F2), all you require for a total loss is to lose the roof. “When this happens, the home loses its structural integrity and must be razed and rebuilt.”

(Up until the 2012 tornado season, Environment Canada used the Fujita Scale to measure tornadoes. It switched to the Enhanced Fujita Scale – considered to be a more modern and improved version of the original scale – on April 1, 2013.)

Of the roughly 500 homes damaged in the pair of Vaughan tornadoes, about 25 had to be bulldozed. In Angus, ten of 100 homes had to be razed due to roof loss. “A roof torn from a house is as good as the entire home being wiped from its foundation,” McGillivray said. “There are no degrees of death.”

Between 1980 and 2009, a total of 1,843 tornadoes were recorded in Canada. The vast majority (91.9% were F0 or F1 tornadoes). F2 tornadoes accounted for 6.5%, followed by 1.3% for F3s, 0.27% for F4s and 0.0054% for F5s. Essentially no new trends have been observed regarding number of tornadoes and location.

“Canada gets about 62 tornadoes a year, the second highest occurrence of tornadoes in the world after the U.S.,” McGillivray told Canadian Underwriter Tuesday.

Most tornadoes occur in central/south central Alberta and Saskatchewan, southern Manitoba, southern Ontario and down through the St. Lawrence Valley.

“However, tornadoes are not restricted to this area, as we have experienced tornadoes in every province, including northern portions of provinces, and in two of three territories,” McGillivray said. “We have also experienced tornadoes in every month of the year, including January and December, though most occur from about May to August.”