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Canada's Climate | Tornadoes

How the Northern Tornado Project unearths twisters

Brad Rousseau

Sunday, December 2, 2018, 3:05 PM - Canada for the most part is a cold weather country, but through the spring and summer months, we see our fair share of severe weather, including tornadoes. 

For several years research meteorologists at Environment and Climate Change Canada (ECCC) have been working on ways to improve our understanding of summer severe weather across Canada with a better understanding of tornadoes, their frequency, and where they occur. As indicated in Cheng et al. 2013, tornadoes across Canada are likely underreported, and this is farther corroborated by Doswell and Burges (1988), who point out that most tornado databases “are often biased and underreported”. 

This can be attributed to many meteorological and non-meteorological factors. In Canada, with so much of the population confined to the southern portions of the country, tornado detection across more rural and northern regions (such as the northern prairies, northern Ontario, Quebec) is quite low. It is well known that strong thunderstorms occur in these regions, but lack of population and observational network makes it difficult to detect tornado occurrence in these regions. (Sills et al. 2012)

This becomes evident when looking at the map below which shows confirmed and probable tornadoes across Canada from 1980 to 2009. Note the large gaps in events across the northern prairies, northern Ontario, and much of Quebec. 

Confirmed and probable tornadoes across Canada from 1980-2009. Note Canada's only F5 tornado occurred in Manitoba. Source: Sills et al., 2012

Sills et al (2012) and Cheng et al (2013) used statistical modeling to try and fill in these gaps. The short and simple explanation, and I encourage anyone who is more interested in the techniques applied to read the papers sourced to get the full scope of the work done, population density and cloud to ground lightning flash density were used to try and fill in the known gaps in the Canadian tornado climatology. Initial results from Sills et al 2012 show that about only 30 per cent of tornadoes in Canada are being verified and Cheng et al. 2013 showed that only about 50 per cent of tornadoes are being verified.

The next big leap in trying to improve out understanding of tornadoes in Canada is with the Northern Tornadoes Project (NTP), a collaboration between University of Western Ontario’s Faculty of Engineering and the Meteorological Research Division at ECCC. 

Initial work from NTP helped to discover Quebec’s largest tornado outbreak in recorded history and one of the largest in Canadian history, which occurred on June 18th, 2017.

The main goals of the NTP are to enhance our understanding of tornado occurrence across Canada, validate the statistical modelling, and improve the detection of tornado damage paths with an emphasis on more rural and remote regions. 

NTP does this by identifying potential tornado damage swaths and using a combination of ground surveys, drone flights, and extremely high-resolution satellite imagery. All the data are analyzed where researchers can identify damage patterns to help determine whether the damage is tornadic, or caused by straight-line winds. They can also asses path length, width, and intensity. If all evidence indicates that damage is tornadic than an EF-scale rating can be assessed. The use of the high-resolution satellite data allows the researches to see whether a damage path through heavily forested or isolated regions is tornadic or not. 

Results from the project have been rather promising thus far. In 2017 the project was able to discover 9 new tornadoes across Ontario and Quebec which led to discovering the largest outbreak in Quebec history as discussed above. But also helped improve data and analysis of 9 other events. In 2018 the project help to uncover 12 new tornadoes across Saskatchewan, Ontario, Quebec, and New Brunswick and helping to improve 10 events across the same regions except New Brunswick. 

Figure which shows the number of new and improved events from NTP from 2017 and 2018 as well as their location.

Noteworthy events from 2018 that the project worked on was the August 3rd EF-4 tornado that struck Alonsa, MB. The NTP helped improve tornado data but more importantly was able to document remote sensing-based indicators which will help with future events (Sills et al. 2018). The project also improved that data from the late season outbreak across southeastern Ontario, including the Ottawa region, and southern Quebec on September 21st, 2018. Of the six confirmed tornadoes, the NTP helped discover 1 of the tornadoes, and researches continue to sift through the data on this event to see if there are any additional damage swaths. In total over 2017 and 2018 the NTP has helped to uncover 21 new tornadoes and improved the data for another 19.

Tornado damage from Dunrobin, ON. From the September 21, 2018 outbreak.

According to Sills et al. 2018 this means the new events have increased the tornado totals by about 30-50% but as previously mentioned the statistical modelling still suggests that actual tornado occurrence could be two to three times as high as the recorded rate. The NTP is important to helping researches and meteorologists have a better understanding of summer severe weather across Canada including the frequency of tornadoes across rural regions and the group involved with the NTP say that "efforts to enhance tornado detection will be intensified in the future."

SOURCES: York University | American Meteorological Society | York University

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