Researchers use hi-res satellite data to track tornadoes in unpopulated areas of Alberta

More than half of tornadoes go unreported in southern Alberta, primarily in unpopulated areas. Now, researchers are using high-resolution satellite data to track tornado damage.

"We've got satellites circling the globe now that can give us daily imagery from areas like forests," said David Sills, executive director of the Northern Tornadoes Project. 

"We can compare one day to the next and see damage that's occurred in a forest well away from any population centres and know that a tornado caused that damage."

Sills is a former severe weather scientist with Environment Canada. He told David Gray, host of the Calgary Eyeopener, that one of the characteristic signs of tornadoes is a long narrow path of damage.

"So it might be just a few hundred metres wide and then tens of kilometres long. So it's a pretty distinctive scar that you see in the forest imagery and they pop right out with this high resolution satellite imagery," Sills said. 

"So we've been finding tornadoes in lots of places that really haven't had that many reports in the past. And even as we're doing that, looking at this year's or last year's tornadoes, we're finding tornadoes from years ago that no one has reported."

Could all this research lead to some way of predicting tornadoes?

"They are difficult to predict," Sills said. "For instance, the conditions last night, you know there were large storms that caused hail to fall, and a couple of the storm chasers had seen funnel clouds. But the conditions need to be just right to get a tornado to form. And so it is very difficult to predict that." 

Sills said the computer models are getting better at predicting these things, but it's challenging. His goal is to provide a "data set of tornado occurrences" that will help verify the predictions of tornadoes — either by computer models or by forecasters when they issue a tornado warning.

Early warnings vital

"If they're issuing a tornado warning up where no one's living, they may not get any feedback or any observations back, and then they don't know if their warning was successful or not," Sills said. "So if we can provide that kind of information, it really helps to fine tune the warning process."

Early warnings are vital, Sills says, adding that Alberta gets about 15 verified tornadoes per year, but that far less than half are spotted or reported.

No reports from moose

"There's these large parts of Canada that don't have a lot of people living there," he said. "And we just don't get reports from the moose. So that's why we really are underestimating the number of tornadoes we get."

Sills said southern Alberta gets the most tornado activity because of its unique geographical conditions.

"One of the really interesting areas is to the east of the Foothills, where you get something called the 'dry line' coming off of the Rockies. A lot of storms initiate there and can produce tornadoes," Sills said.

"So there's this area west of Calgary and then going through Calgary and then Medicine Hat, that kind of area where there's there's a lot of these ... thunderstorms that can produce tornadoes. That dry line is really important, an important mechanism that's particular to Alberta through that area that really needs to be monitored — and that's what you can base your warnings on."

Sills said knowing more about tornadoes, and tornado-prone areas, is important for building codes and for knowing how and when to warn people. The program is now Canada-wide, with an aim to detecting every tornado across the country.

"We are finding that we're only detecting 30 to 50 per cent of the tornadoes that are occurring," Sills said. "It's a big country."

With files from the Calgary Eyeopener.