You might think that tornadoes should be easy to spot. They reach out like gnarled fingers in the heat of storms, pulling trees out of the ground and pulling cars off the road, picking up Kansas farms and transporting them to the land of Oz.
But things are not so simple in Canada, or in any sparsely populated region. Canada is huge—it’s the second largest country in the world by land area, after Russia—but most of its residents live near the US border. As a result, many Canadian tornadoes end up touching down in areas without witnesses, leaving the country’s tornado census notably incomplete.
Until just a couple of years ago, the average number of confirmed Canadian tornadoes per year was around 60 (enough to earn its place as the country with the second most tornadoes in the world, behind the United States, which averages around 800 a year), although scientists calculated that the actual number should be closer to 150.
Such paucity of data is both unsatisfactory and dangerous. Tornadoes can be deadly and their property can be expensive. Their frequency, location, and severity are not always well understood and may also be changing. “If we’re ever going to pin down how climate change is really affecting these things, we need a precise quantification of not just how many tornadoes occur, but also where,” said Ian Giammanco, a meteorologist at the Insurance Institute for Business and Business. Home security. He added that knowledge of tornado trends could help warn people of future storms and guide building and infrastructure codes.
Recently, a group of meteorologists and weather scientists from the Northern Tornado Project at Western University in London, Ontario have been trying to address this deficiency. Using social media and eyewitness reports, satellite imagery, drone footage and downed trees, the group has tracked more Canadian tornadoes than ever before. In 2021, a record for the most confirmed tornadoes in one year was set: 117. In 2022, that record was tied; 80 of those tornadoes were verified by the Northern Tornado Project alone.
Such a drastic increase probably does not reflect an upward trend in the number of Canadian tornadoes, the scientists said, but rather the additional scrutiny they are receiving.
“We’re putting a lot more effort into finding these things,” said David Sills, a meteorologist and director of the group. “We are trying to have an impact.”
The first step in tornado detective work is figuring out where to look. Tornadoes form when cold air pushes down against warm, rising air under the right conditions. This can happen in many different types of storms, although the largest and most destructive tornadoes come from supercell mesocyclones—tall columns of rotating updrafts in large thunderstorms. Precipitation in the storm cloud pushes the mesocyclone downward, and as its parts become pressurized and exposed to different temperatures, a funnel is created. When this funnel hits the ground, it is classified as a tornado.
The tornado recipe is most likely to work in places where there is a constant supply of cold air (often from the mountains) and warm air (often from the tropics). A classic example takes place in the Great Plains of the United States, where the humid and warm air of the Gulf of Mexico meets the cold and dry air of the Rocky Mountains. More tornadoes occur there than anywhere else on Earth.
In Canada, most tornadoes appear in Alberta, Saskatchewan and Manitoba, the so-called Prairie Provinces, and Ontario. Scientists with the Northern Tornadoes Project are keeping an eye on the weather radar in those regions and another on social media, looking for reports of strange weather events.
Much of the work, then, is retrospective, using evidence on the ground to reconstruct a storm after it has passed. What were the wind speeds? Which path did the storm take?
Tornadoes are often confused with downbursts, columns of wind that push toward the ground and spread out radially. Downbursts can precede tornadoes and form in similar weather conditions, but usually do much less damage; confusing one with the other can skew the data.
Satellite images sometimes do not help in these cases; a single pixel in a satellite image corresponds to nine square meters of land, enough resolution to determine just that some type of high-velocity wind event passed through the area. “You have to get a plane or a drone,” said Connell Miller, a weather scientist with the Northern Tornadoes Project.
This is the key step for tornado detectives. Dr. Miller said details of each storm appeared in high-resolution photos captured by drones and aircraft. Trees falling on each other indicate a tornado, while trees falling in the same direction indicate an outburst. A long thin path of destruction: tornado. A wide path of destruction: downburst. Two parallel paths? A multi-vortex tornado. Roof tiles ripped from barns, crops torn from the ground, billboards blown up in the woods—all of this information helps scientists reconstruct the tornado, understand how it formed, and what kind of risk it posed, or would pose, to people and infrastructure.
Dr. Sills said that even in unpopulated areas, tornadoes can destroy power lines and start wildfires, so their impact is palpable. But the main goal is preventive. “People want to increase the resilience of their communities,” he said. Better research manifests itself in revised building codes and warning systems: every storm counts.