The Canada Day tornado that rocked central Alberta on Saturday afternoon was rated an EF4 on the Enhanced Fujita scale, making it the highest-rated Alberta tornado since Edmonton in 1987..The massive tornado hit near Didsbury, 80 km north of Calgary..READ MORE: UPDATED: Tornado hits near Didsbury, homes damaged.The Enhanced Fujita Scale or EF Scale, which became operational on Feb 1, 2007, is used to assign a tornado a rating based on estimated wind speeds and related damage..When tornado-related damage is surveyed, it is compared to a list of Damage Indicators (DI) and Degrees of Damage (DoD) which help estimate better the range of wind speeds the tornado likely produced. From that, a rating (from EF0 to EF5) is assigned, with EF5 being the highest.."The survey teams found that there was enough evidence to rate the tornado damage at EF4, with a maximum wind speed of 275 km/h. The preliminary path length is 15.3 km and maximum path width 620 m," the Northern Tornadoes Project (NTP) stated in its report.."Twelve residences were hit by the tornado, three were destroyed, four were left uninhabitable, and a further five were damaged.". Alberta tornado .NTP said one of the houses that was destroyed was found to be well-built after an on-site engineering analysis.."Using the EF scale tool, DI was 'One- or Two-Family Residences (FR12)', and the DoD was nine - meaning all walls collapsed. Given the house was well built, we could use the 'expected' maximum wind speed for DoD9 of 275 km/h. The wind speed range of EF4 is 270-310 km/h. So, the EF rating is low-end EF4," NTP said.. Large tornado in Mountain View County,Large tornado in Mountain View County, ."In terms of nearby corroborating damage, various farm equipment was flipped and thrown at that property. This includes a combine weighing almost 10,000 kg that was thrown at least 50 m, and then rolled for another 50-100 m after that," NTP said.."Wind tunnel studies of another combine that was hit by a previous Canadian tornado suggest a wind speed of 230 km/h for just flipping a combine. Tree stubbing/debarking and ground scouring are also consistent with a high-end tornado.". damage from twisterA farm roughly 48 km North of Calgary. .Thankfully, due in part to timely weather alerts, there was only one minor injury (a cut to a first responder, apparently)..Climatologically, the Didsbury EF4 tornado enters some rarefied territory among Canadian tornado events, NTP added.."It is the strongest recorded tornado in Alberta since the Edmonton F4 tornado of 1987 and one of only three tornadoes rated F/EF4 in Alberta (the other hit the Grassy Lake area in 1915)," NTP said.."It is only the second tornado in Canada to have damage rated at EF4 on the Enhanced Fujita scale that was implemented in this country in 2013, with the other being the Alonsa, MB EF4 that also had a maximum wind speed of 275 km/h.".Across the country, there have been only 21 'violent' tornadoes rated at F/EF4 or higher..One of these was Canada's only tornado rated at F5 - the Elie, MB tornado of 2007. Most of the others have been in southern Ontario, although Saskatchewan and Manitoba have also experienced F4-rated tornadoes (three in SK, all 1920 and earlier; two in MB from 1977 and 1994).."Though this was a climatologically significant tornado, it thankfully won't enter the list of Canada's top ten 'worst' tornadoes due to the single minor injury and limited property damage," NTP said.
