Western experts talk tornadoes: predicting, mapping, protecting people and property

On May 21, 2020, tornado and extreme weather experts Greg Kopp and Dave Sills took part in a webcast to discuss the upcoming tornado season and how to best detect tornado occurrence throughout Canada. Topics included predicting severe and extreme weather, mitigating damage, implications due to climate change and the role of citizen scientists in these changing times. Sarah Dawson, Western Alumni Career Coach, was host of the webcast and also relayed viewers’/listeners’ questions to the experts.

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Sarah Dawson: Good afternoon everybody. Welcome to today’s webcast on the Northern Tornadoes Project. I’m Sarah Dawson from Western Alumni.

The Northern Tornadoes Project is a partnership between Western University and ImpactWX, which is a Toronto based social impact fund, with a mission to enable organizations like Western and through scientific understanding and public awareness, work to improve people’s response and safety during severe weather events. The Northern Tornadoes Project does just this: it actively works to develop new methods and tools to inform the field of severe storms research. Constantly striving to be a community endeavor, the Northern Tornadoes Project believes it will take the efforts of the full severe-weather community of scientists, storm enthusiasts and media outlets to ensure the project’s success across the country, especially now during the pandemic.

We’re joined today by two of Canada’s leading research experts on tornadoes and extreme weather, Greg Kopp and Dave Sills.

Greg Kopp is the ImpactWX Chair in Severe Storms Engineering at Western’s Department of Civil and Environmental Engineering. His research is focused on mitigating damage to structures during extreme windstorms such as tornadoes and hurricanes.

Our next panelist is David Sills, the Executive Director of the Northern Tornadoes Project. Before coming to Western last year, Dave worked for more than 20 years in the severe-weather science area with Environment and Climate Change Canada, conducting research on Canadian tornadoes, severe nowcasting and massive scale meteorology.

Thank you both for joining us. I’m going to start off with something basic: tell us what a tornado is.

Frank Neufeld // Western NewsDavid Sills is Executive Director for the Northern Tornadoes Project based at Western.

David Sills: A tornado is a violently rotating column of air that is in contact with the surface, either water or land, and in contact with the storm’s updraft. It can be over water, like a lake or an ocean, and that’s usually called the waterspout. Or it can be over land and we generally call that a tornado. Often, the rotating circulation lowers the temperature and pressure in that vortex and generates a funnel cloud.

Sometimes this funnel cloud extends partway to the ground, sometimes fully to the ground. So you can have a combination of a funnel cloud aloft and all kinds of dust and debris and damage occurring at the ground, or that big cone funnel that everybody’s used to seeing from the cloud right to the surface.

Sarah Dawson: Tell us a little bit about why it’s important to detect and identify every tornado in Canada.

Greg Kopp: It’s important because of risk modeling that we do as engineers. When we look at risk, we need to know where tornadoes happen and if we’re missing a large number, then we don’t have a true picture of the risk. Some of the most severe tornadoes seem to happen in outbreaks and if we don’t get a picture of the true number of them, we’re not going to have a good handle on how much risk we have.

Sarah Dawson: Do you find that you are identifying more tornadoes with this project than would have been identified in the past?

David Sills: Sure, that was the goal. We assumed that we were missing a lot of tornadoes because most of the tornadoes that were reported in the past had been in the areas with cities and towns, and a lot of Canada is forested or crops. And when we started really looking in the last few years, we discovered more than 100 tornadoes that otherwise wouldn’t have been documented.

In the first couple years of the project, 2017 and 2018, we focused mostly on Ontario and Quebec and we tripled the number of tornadoes that were counted in those two provinces. So, it’s been quite eye-opening to see how many more tornadoes are occurring than we would have normally discovered.

Sarah Dawson: If these tornadoes wouldn’t have otherwise been discovered, what kinds of tools and technology are you using to discover them now?

David Sills: Well, it’s a process that begins well before the tornadoes form. We have a team of meteorologists that try to forecast conditions for tornadoes, even a couple days out, just to be aware of that possibility and also to alert our team that we may need to jump on a plane and go do a damage survey.

Obviously, that’s not happening right now but that’s generally how we use the forecast. It allows us to pinpoint an area of interest. Then as the event is going on, we can monitor radar, which is becoming an increasingly useful tool with the new radars being installed across Canada, and also monitor the flow of information that comes in over social media channels to tell us exactly where the action is happening with these storms.

Once we know roughly where the storms have occurred and if there may have been a tornado or may have been damage, then we can start using our more high-tech tools like the high-resolution satellite imagery that can really detect tornado scars in forests and tornado damage in cities sometimes. When we’re able to get out, we can launch drones and they pick up very high-resolution data to the point where we’re seeing every tree, which way it was found, what the soil conditions were, and that gives us a really good idea of whether this was a tornado that occurred and caused the damage or if it was a downburst, or straight line.

Sarah Dawson: Many people really enjoy watching a storm roll in. A tornado feels a bit scarier, certainly more ominous. How far out you can predict a tornado and with what kind of accuracy?

David Sills: Well, the ability to predict tornadoes is increasing. Over the last decade, there’s been a lot of advances, and especially in numerical weather prediction and computer modeling or computer simulation of the weather. And, while that doesn’t give us a precise time or location of a tornado, it gives us an idea that the conditions that will produce a tornado, the instability in the atmosphere, the wind shear and the jetstream and so on, will be in just the right place to produce tornadoes.

So that’s how the NTP forecasters can look out a few days ahead and say, ‘Oh here’s an area that looks like it’s going to produce a tornado,’ because those ingredients are coming together. At it gets closer to that day, the forecast tends to get better so you can pinpoint that area and get a smaller area of interest. And then on the day of, it’s a matter of looking at high-resolution satellite imagery and the radar imagery to get a sense of where storms are occurring, and which ones might be able to produce a tornado.

Sarah Dawson: Are you able to make predictions seasonally? Would you for instance be able to determine, based on the predictions about the weather in the coming months, we think we might have a summer where we have a high risk of tornadoes?

David Sills: There’s been quite a bit of research on that in the United States, where they’ve looked at the teleconnections like El Niño and La Niña, and another teleconnections that are global weather patterns and how they might affect the upcoming tornado season. There’s been some success just in the last few years with being able to predict that – the seasonal forecast of a tornado. We haven’t really looked at our data to see if there are these connections yet but that’s something that we can do in the future.

Sarah Dawson: Your viewers really want you to do that right now.

David Sills: Note taken.

Sarah Dawson: When you think about the impact that your research has on how we build structures to withstand tornadoes, Greg, could you speak a little bit to that in terms of what we’re looking at with winds and how we can identify and determine wind speeds in tornadoes?

Greg Kopp

Frank Neufeld // Western NewsEngineering professor Greg Kopp is Project Lead for the Northern Tornadoes Project, based at Western.

Greg Kopp: The first part of that is, can we do anything about tornadoes? Part of our detailed damage surveys includes taking note of how our buildings perform during tornadoes. Houses aren’t designed for tornadoes so when they go through these super events, it’s not surprising that there’s damage. But we can learn from that damage, and we’ve been doing that for a number of years.

Some of the fixes can be pretty easy. One of the most vulnerable parts of a house is the roof. And we typically think of a strong house as one where the walls are strong, and you don’t want the roof to fall in on you. But in a windstorm, you do the opposite, you have to hold the roof down. And we can do that. There’s technology to do that for hurricanes in South Florida and we can apply that to houses in Canada and keep the roofs on. If you keep the roof on, you eliminate a lot of the damage.

We have a project right now with some builders in St. Thomas implementing our findings on that, and we’re learning from the builders how to do it in a more cost effective, efficient way. And we believe we can design houses for 90-95 per cent of the tornadoes, to keep the roof on and keep the structure intact, for only a few hundred dollars per house.

Your second question about the wind speeds is related to that damage. When we observe this damage, as engineers, we can work out how strong a structure is. We can do wind tunnel testing and learn about the aerodynamic forces and when we put all that together, we can estimate the wind speeds that caused the failure.

So, when the media reports wind speeds of 200 kilometres an hour, no one measured that wind speed, we estimated it from the damage that was observed.

And that’s what the EF scale is, which has these damage indicators and different levels of damage, and from that we estimate the wind speeds that would cause that damage. So, you can think of them as a good guess but as engineers, we think of them as a pre-calculation.

Sarah Dawson: Today marks a significant weather day in history here in Southwestern Ontario: nearly 67 years ago, one of our nation’s most violent outbreaks took place. Can you speak about this storm and how has detection and prediction changed since this incident?

David Sills: So, that was the May 21, 1953 event. And it started just across the border in the States, an F4 tornado that went right through Sarnia. But throughout that day, there were three more F4 tornadoes, another that was an F3, another that was an F2. And putting all that together, it was the most violent tornado outbreak that we’ve had across Canada. But because it didn’t hit a lot of highly populated places, the amount of damage and fatalities and injuries weren’t as high as some of the other big tornado events in Canada that show up on “top 10” lists. But as far as just the sheer number of violent tornadoes in one event, that’s the top end.

It did cause a lot of damage in and around Sarnia and initially it was thought that the damage was due to just a couple tornadoes. We reanalyzed that and found that was due to two more tornadoes, so we’ve got four F4 tornadoes now, plus the F3 and F2. And if today we went out and did that survey again, we would probably find that many weaker tornadoes also occurred. Because with these outbreaks you tend to get quite a few strong tornadoes, but then a bunch of weaker tornadoes around that are hard to pick up. And back in 1953, there wasn’t a lot in the way of satellite imagery, or anything like that to help us; the data was mostly taken from newspaper articles.

Sarah Dawson: What constitutes an F4 tornado? How do you distinguish?

David Sills: Well, you estimate based on the damage caused. In the case of an F4 tornado, you’d expect that a house would be destroyed, basically. The roof comes off at F2, some of the external walls come down at F3, by F4 all the walls are down. And if you go even higher than that, to F5 which is the highest on the Fujita scale, then the entire house is swept away from the foundation and there’s nothing left.

Just to be clear, for those historical tornadoes, we used the Fujita scale. But since 2013, Canada has adopted the Enhanced Fujita scale. It’s the same damage associated with the same category, 1-2-3-4-5, and it’s just the wind speeds that have changed associated with those particular F-scale categories.

Sarah Dawson: In Southwestern Ontario, there appears to be more severe weather and tornadoes in the July-to-October timeframe, versus 30 to 40 years ago when it seemed the March-to-June timeframe was more dangerous. Do you have any ideas of possible reasons for the change?

David Sills: It’s interesting that question came up because I’ve got a summer student working on that very question right now. And that has been something that the forecasters at the Ontario Storm Prediction Centre have noticed as well. In 2018, the big events in Ontario were late September, so what’s going on here? Connor, my student, and I are going through all of the Ontario data back to 1792, and looking to see if there’s some kind of pattern and if we can use that pattern to predict what will happen in the future.

Sarah Dawson: Can you explain why, when a tornado comes through an area, it might take out one house completely but the one standing next to it appears to be untouched?

Greg Kopp: We see that in events. Remember the outbreak in 2009 that hit suburbs of Toronto and there was one house that lost its roof and right beside it, the neighbours had lost the few shingles and the whirlybird off the roof? There are a number of causes for that.

One part of it could be that houses are not engineered, and they’re built by builders so if you look at the structure underneath each of them, they’re all a little bit different. And those details matter, quite a lot. Sometimes the performance in this particular event in Vaughn, what happened was the front door blew in, and it kind of pressurized the house and it blew the roof off with it, and the neighbour’s house, the door didn’t go in and that was probably why the roof didn’t go off.

The other part of it is the nature of turbulence. Tornadoes are turbulent – there’s gustiness and all of that occurs differently. You and I could be standing a few feet apart but the wind we feel is going to be a little bit different. Tornadoes have a complex structure: some tornadoes are made up of multiple little vortices spinning by, others are one single large vortex spinning around. So, you get this different behavior just by those subtle differences and when you add them up, you see some strange things happening.

Sarah Dawson: I think public perception of tornadoes and severe storms is influenced by things we’ve seen in the movies like The Wizard of Oz. What do we need to know about the conditions necessary for a tornado, and do those make it more likely for something to happen at a particular time of the day?

David Sills: The conditions that typically lead to tornado formation are those that are present usually in the late afternoon/early evening, when you’ve got the maximum heating of the day, all the solar input into the atmosphere, and a lot of the energy is getting released through this big thunderstorm and then the strong updrafts that drive a tornado. So, most of our tornadoes occur during the dinner hour.

Obviously, there are examples where they occur at other times – they can even occur overnight. Sometimes it’ll just be the timing of a cold front that’s coming through and generating all this strong thunderstorm activity overnight. And so, you’ll get a big tornado occurring overnight and those are more terrifying because you can’t see them.

And sometimes tornadoes are what’s called rain wrap where there’s a lot of rain generated by a thunderstorm, and the rain wraps around the tornado itself through the rotating motion of the thunderstorm and then you can’t see the tornado. But, again, they mostly happen around the dinner hour but they can happen at any time.

Sarah Dawson: Is there a geographic place in Canada where tornadoes are more prevalent?

David Sills: That would be Southern Saskatchewan. That’s what we believe. As I mentioned before, there’s all kinds of places in Canada with not a lot of population but we know they get severe thunderstorms. So, a while back, we did some statistical modeling to try and fill in the gaps and determine where tornadoes are really occurring. And part of what we’re doing with NTP is trying to validate that model and confirm that tornadoes are occurring in these areas. The model showed that the maximum should be in southern Saskatchewan. And judging by the number of storm chasers that spent time in Saskatchewan in July, I would say that’s probably correct, that Saskatchewan probably gets a lot of tornadoes in the July/August period.

David Sills // Special to Western NewsDavid Sills, Northern Tornadoes Project Executive Director, shot this photo of a bolt of lightning in an angry sky across a field of ripening canola.

It’s funny in the prairies, the season starts slowly, and then in July and August, there’s a lot of activity basically on par with what you’d see in Tornado Alley in the United States and then it shuts down pretty quickly. Whereas in the United States, there are places that start their tornado season in February, March, and go through the year so it’s no surprise they get more tornadoes because their season’s so much longer. But when our season is in full swing, it’s every bit as strong and intense as parts of the States.

Sarah Dawson: How does Western research detect tornadoes in uninhabited parts of Canada?

Greg Kopp: Well that’s part of our research. I was going to respond to the last question too. If the tornado doesn’t hit anything, then the rating is low, we just know that there was a tornado. So, you can have a very intense tornado but if it doesn’t hit anything, we don’t have a way of rating it. So, we’re trying to find other indicators.

In 2018, the most powerful tornado in North America happened in Manitoba, in a town called Alonsa, and one of the things we saw there was that we could see the track of the tornado in some areas really clearly through the grassland. And when our students were there doing the damage survey, we had them go and try to find what was wrong on the ground. It was just some dead grass and it comes out really clear in the satellite imagery, but it’s hard to see on the ground. So, we’re trying to use information like that – how the grasslands are affected, how crops are affected, how trees are affected. And we’re working on ways to get better estimates of the intensity of them, not just how they broke, but the patterns that might have emerged and relate those to wind speeds. Now those like Alonsa, when you have an event like that, then it goes over house but also its adjacent grassland, we can find ways to correlate that information. So, we’re trying to develop tools to do that but it’s a really challenging problem.

Sarah Dawson: How can citizen scientists help you with your research?

Greg Kopp: If they can tell us what they see and report that, that’s fantastic. On our website, you can enter information and you provide details about what you saw. We also have Twitter hashtags @WesternuNTP and we do extensive searches of social media to identify events so if you use our hashtags, we see them really quickly, and we can use that to contact people and find out more information. That’s a good way of reaching us.

Sarah Dawson: The powers of observation are valuable in your research.

Greg Kopp: They are. And as Dave said, in southern Saskatchewan where there’s not a lot of things that can break but there are a lot of storm chasers, they become an important conduit to us for when tornadoes are happening. We won’t be able to get their intensity, but we can at least note that they happened.

Sarah Dawson: Is there a safe distance from which you can observe tornadoes and severe storms?

David Sills: Well, as someone who has storm-chased and tornado-chased, both for pleasure and for work, it’s inherently dangerous. And even if you think you’re far enough away, the storm can change direction on you and suddenly you’re in trouble. So, it’s not something I recommend, unless you know what you’re doing out there as far as understanding storm structure, how to interpret radar and all that kind of thing.

But, if you are well educated as far as how storms behave and keep your distance, you can see some interesting things regarding the whole storm structure. And use that zoom lens to get in close to the tornado, there’s no need to be right next to it. Some chasers want to be right there, but you can chase and get close to the tornado without even getting wet.

I did a program in the United States, Vortex2, where there was a bunch of instrumented vehicles, and each of us had a task around the tornadic thunderstorm where we were to drive in, do sampling and drive out. And my partner, Neil Taylor, and I decided we were going to take the safe route and stay on the inflow side of the storm where there was no big hail and we could see things at a nice distance. Some of the younger graduate students and staffers were much more excited to be right in the core of things and you’d see them disappear into the hail core and then they come out the other side with their windshield all smashed, a two-by-four through the window and they’re like ‘yeah, alright!’ I mean, we’ve got families at home, we’re not interested in that. So, there’s a real range of how much trouble you can get into when you get close to one of these things.

Sarah Dawson: Is there any trend that you see in terms of the colour of the sky before a tornado touches down?

David Sills: Many people report that the sky changes colour and for sure with the tornadic storms that I’ve seen, they tend to have shades of green and brownish-yellow sometimes. Sometimes that’s due to the sun angle if these storms are occurring in the evening. The sun can get underneath parts of the cloud and change the look of the storm. But the green part, a lot of people see that even with storms that don’t have tornadoes. This brilliant green or sometimes bluish color is often due to sun filtering through hail before it gets to your eye. And so that’s a giveaway that you’ve got a strong and severe thunderstorm, but it doesn’t necessarily mean that you’re going to get a tornado.

Sarah Dawson: What are the early signs that people could look for as the storm is approaching?

David Sills: The strongest tornadoes tend to occur with what’s called supercell thunderstorms. These are storms where all the action is at the back end. You’ll see a storm approaching and you might get light rain initially, and with big dark clouds on the horizon, the rain gets heavier and then all of a sudden you’re into hail, then very large hail and then all of a sudden there’s silence and everything stops. That’s the danger zone. That’s where the updraft of the storm is and if there was going to be a tornado, it would be in that area. If you pay attention to that progression, if you’re getting hail and suddenly there’s quiet, be on the lookout for a tornado at the back of that storm.

The other type of storm that generates tornadoes is more like a line of storms, and in this case the storms, the tornadoes form along the leading edge of the storm. So you’ll see a big shelf coming, called shelf cloud, with kind of dark cloud and a horizon with kind of fingers dangling down, and sometimes you’ll get rotation developing along that leading edge and that rotation gets sucked up into the updraft and intensifies to a tornadic strength. Those tend to be weaker, but they still can cause damage. And so again, they’re at the beginning of the storm, not the end of the storm.

And there is one other kind, which is a big thunderstorm forming and explosively developing and right as it’s developing that updraft is strong and happens to have some rotation underneath it that gets stretched. And kind of like a skater bringing in their arms, getting faster and faster, that initial surge in the updraft can lead to the development of tornado at the surface. Again, those tend to be weaker tornadoes and they’re called land-spout tornadoes because they look like what a waterspout looks like over water.

So, there’s several different ways tornadoes can be generated. But the most significant tornadoes, the ones that generate the F4s and F5s are almost always supercell tornadoes, these ones with all of the activity at the back of the storm, and those are the ones to really watch out for.

Sarah Dawson: Last year, a rather visible tornado touched down in Ottawa on June 2. The supercell appeared to be relatively low-topped. Has the set up for this storm been uncovered and could this have been a cold-source setup?

Northern Tornadoes Project // Special to Western NewsDamage from an EF3 tornado in Dunrobin, near Ottawa, in September 2018. It was the strongest of a cluster of six tornadoes that day.

David Sills: Sometimes we do get these low-top storms. You expect in a summer storm that you’ve got lots of warm and lots of moisture and lots of instability, and the storm grows very tall and looks very impressive, but sometimes the conditions that lead to a storm aren’t quite like that. They’re less vigorous as far as the convection, there’s less moisture feed and the storms don’t get that tall. But depending on the wind shear, how the wind changes with height in the atmosphere, those can be dangerous as well, you can get a low-top supercell thunderstorm and again get that rotation. So, I’m not particularly sure about the event he’s talking about but definitely we can get those types of events, it all depends on where the storm develops relative to say a low-pressure system or disturbances in the upper atmosphere.

Sarah Dawson: What’s the most surprising information that you’ve discovered in your research?

Greg Kopp: Well, when you do damage surveys you do see strange, strange things. When you see a two-by-four going through a concrete barrier, that always kind of surprises you. You see the walls sucked out of the side of a house and the pillow and the bedding are still perfectly in place, it always surprises you. We try to uncover why those kinds of things happen but you see some fun things and some, well, some sad things.

Sarah Dawson: Is this mostly a wind engineering in climatology project or are you investigating the physics of tornadoes in the tornado lifecycle?

Greg Kopp: I would say we’re doing both. It’s a collaboration between engineers and meteorologists and data scientists and all sorts of different parts of our team. So, my perspective is on the engineering and capturing all the data that we can from the storm. Dave obviously is working on the meteorology and we have a team of meteorologists as part of the team looking at the forecasting. We have a longer-term vision to develop and improve nowcasting techniques for Southern Ontario and perhaps the rest of the country as well.

Western Libraries are involved to host all our data, we have literally terabytes of data that are being stored and are publicly accessible. We’re collaborating with experts in machine learning and artificial intelligence to help analyze that data so we can get better estimates of the intensity of the storms as we talked about, like literally identifying tree-by-tree that’s down, the direction it’s facing, etc. Right now, we’re doing that by hand to develop some of these tools, but we want to use machine learning. When you have a track of 40 or 50 kilometers, there’s tens of thousands of trees down and we’re trying to identify each one of those. And then run that through special tools to say, ‘well what was the wind speed and wind speed pattern of this tornado that caused that damage?’ so we can get a better estimate of that intensity of the tornado.

So, there’s all sorts of people involved in this and everything we’re doing is open and you can find it on our website. Right now, it’s primarily data sources that are there and you can see what we’ve identified, what we’re currently working on. But in the next few years, there’ll be more tools there to help with identifying the intensity and hopefully these are useful to researchers. We’re still thinking about how we can develop tools for the public to help them engage with this kind of work as well.

Sarah Dawson: How are GIS and remote sensing used in this project?

Greg Kopp: Well, everything is using GIS (graphical information systems). GIS is a way of looking at maps with detailed points on it. So, all our imagery or photographs from satellites, from aircraft, from drones are modeled in GIS and we know exactly where that image is in the world. And then the remote sensing, this is a way of identifying the damage so we’re using a whole range of tools for that. We use satellites as one of our primary tools. The earth is imaged every day now so we can see before and after imagery from the storms.

Dave talked earlier about using the radar and seeing where the storm tracks are going but we can then use the satellites to see before and after to see what kind of damage path was there. Then we fly aircraft over to get imagery, the latest technology is using drones, and we get very accurate imagery for that, down to centimeters so we can start to see structural details on the ground. We can see where the trees are, where they’re pointing. And we can put all of this together to analyze. So remote sensing, and the changes in that technology in the last few years, has really helped us quite a lot.

Sarah Dawson: Have you noticed any changes in your ability to get information in the past couple of months? Because a lot of planes aren’t flying right now, has that had an impact on your research at all?

Greg Kopp: Well, there hasn’t been much yet happening in Canada, so it hasn’t affected us, but we are planning for how we’re going to be doing this year. And this year is going to be primarily through remote sensing so it’s kind of an experiment for us in a way to see if we’re maintaining our goal of trying to identify every single tornado that happens in Canada this year. We also need the crowdsourcing and citizen science work to help us.

We have permission from the University to continue doing our drone study so in southern Ontario, to places where we can drive, we will continue to go with the drones because we don’t have to have much interaction to do that, either with the public or within the team, and so we can do that safely and capture that kind of data. I mean, when these things happen we view that as our science experiment and we’re trying to capture that data –and it’s perishable data, people start cleaning up immediately and so we try to get there as fast as we can to capture that and then use it in our analysis.

Sarah Dawson: Okay, is there storm chasing involved in your work right now?

Greg Kopp: No.

David Sills: We do have a few car-top weather stations that are in storage right now, and we might come up with a way to use them in the future. But, at the moment, no, there’s no storm chasing involved.

Sarah Dawson: Are we now able to better detect storms or does climate change have an impact on storm frequency? Are we seeing changes that you think are connected to that?

David Sills: This is a hot topic of research, how climate change is affecting things like tornadoes. It’s easier to see patterns in temperature and precipitation because those kinds of observations are much more widespread, millions of observations across the planet, whereas tornado events are not measured by a weather station, you have to go out and investigate them. They’re quite rare really compared to things like temperature measurements or rainfall measurements so it takes a while to build up a database that you can reliably use to determine climate trends. That’s part of the reason for doing this project, to build a high-quality database so that we can look at these patterns.

There has been a bit of work done in the States on this and one study shows that the actual number of tornadoes hasn’t increased that much but when tornadoes do occur, there’s more of them. So, there’s more clustering of tornadoes. We haven’t looked for that in our data set yet, but we probably will.

Another recent study has shown that the region known as Tornado Alley in the United States is beginning to shift. Right now, the central plains, the high plains of the States, that’s the traditional Tornado Alley, but the research is showing that it’s just starting to drift slightly over towards the northeast and into much more populated regions which is really bad news. Whether that’s happening in Canada or not, again we haven’t looked at that and we need to build a database to do that kind of work.

Sarah Dawson: Do you think tornadoes will become stronger than F5 in the future given climate change?

Greg Kopp: The F5 is a damage scale and so it depends on the structures that are being hit. A lot of our work on trying to understand how to build stronger houses also tell us how they come apart. Houses are the most common structures, so we use those to identify things. So, if there were something stronger than the F5, I’m not sure if we could identify it from the damage. There’s no way of getting at that, at least from a common perspective.

David Sills: There is ongoing work to try to identify the strength of a tornado using mobile radar. Mobile radars are used quite often in the States – they get close to a tornado and try to take measurements low down to try to get the maximum winds in a tornado. And sometimes they’ve measured wind speeds that are a bit higher than what we consider to be the highest end of the EF scale.

Those kinds of measurements aren’t incorporated into the EF scale in an official way, but there’s work being done to try to bring in those types of measurements and use them to characterize the strength of the tornado. So, maybe in the future we’ll have a radar measurement that can be verified. But as Greg said, just looking at damage once the house is wiped off the foundation, it’s hard to get an idea of how much more damage could be done.

Sarah Dawson: Is the data being gathered going to enable us to build safer houses? Greg, you mentioned a low-level cost investment in making a roof stronger, are there other measures in addition to that?

Greg Kopp: Well that’s part of what we’re trying to do, to make changes to building codes or to design for extreme wind. And as we gather a larger and larger database, especially for stronger tornadoes, we can see how well our built environment performs and we can learn from that.

We’re right now working on a standard in Canada that CSA is working on to design houses for extreme winds, focusing really on tornadoes and that’s unique in the world. The only things that are really designed for tornadoes right now are nuclear reactors. The electrical grid, which, if you think about that, spans the continent. It’s like a big tornado net so it’s going to be hit. Transmission towers are starting to consider tornadoes, at least, thinking about the roads and diversifying the risk at least for those kinds of structures. One city in the U.S. has a building code for tornadoes in rural Oklahoma and they of course got hit with several massive tornadoes over the course of two decades and they finally decided to do something about it.

So, 90 to 95 per cent of tornadoes are EF2 or less and EF2 means the roof comes off the house. You want to think of that in a simple way and we can keep roofs on for much less money and even in a devastating year for F5 tornadoes only part of the track has that intensity; the bulk of the track has much less damage and so we can reduce that by designing for these structures and designing for these kind of winds. And if we do that, we also keep a lot of the debris out of it, so if your roof flies off, that’s bad for you because your house now is gone. But your roof might hit your neighbour’s house and if your neighbour’s house might otherwise have survived, but now it got hit by your roof and it’s also destroyed, you get this cascading damage. So, we think holding the roofs on is a critical thing to making all of us much safer in tornadoes.

Sarah Dawson: Someone in the live chat was in the 2013 tornado in Moore, Oklahoma. They say they remember when the tornado hit that their ears popped from the drop in pressure and they wonder how much damage is attributed to low pressure, and how much of it is due to wind speed?

Greg Kopp: Well, that’s a question that’s still being debated amongst the researchers. And you have two parts of it. The low pressure is in a sense the driving force for the wind that’s swirling around. And so it depends on a lot of details for small structures like regular houses, that low pressure’s probably not changing the forces acting on the house very much but for large buildings – think, your large Walmarts and those kind of structures – there is an increasing body of evidence that low pressure in the tornado is also contributing to the damage in some way. So, I’m going to maybe sound wishy-washy but I’m going to say it depends. It’s going to depend on the nature of your structure and things like that.

David Sills: But there is this old myth that, due to the pressure, you want to open all your windows if you think a tornado is going to be coming to make sure that pressure doesn’t build up. And in fact, Greg’s work has showed the opposite – that if you think a tornado is coming, the windows and doors should be shut to seal the building envelope. That’s much more important. So, you know that’s one myth that comes out of this whole pressure idea that I think the engineering sciences has really addressed in the last decade or so.

Greg Kopp: Let me add to that. So, if you have time, close the windows, if you see it’s coming, just head to the basement. If you have enough time though, if you’ve got a warning of a few minutes, I would say not only close all your windows, close all the inside doors as well. That will help. And that’s research that just come out from the U.S. in the last year or so. That would be the guidance but head to the basement if there’s something happening.

David Sills: If there’s a tornado watch issued well ahead of the event, that’s the time to start thinking about these things. Make sure that everything’s closed up tight, make sure you’ve got a pair of shoes around because if something happens to your house you don’t want to be in bare feet. So, it’s time to start thinking of your plan if there’s a tornado watch issued. By the time that tornado warning is issued, you better be moving into the basement or somewhere safe.

Sarah Dawson: Kyle is asking if photogrammetry can be used as a valid method to determine wind speeds as part of that EF scale, and why can’t mobile Doppler measurements?

Greg Kopp: I’ll take the first part. I mean Fujita used photogrammetry to estimate wind speeds from debris moving through the wind field so that’s not a new technique. I think the hard part of that is calibration to get an accurate estimate from it, but I think it’s something that can be used. You have to be there and you have to plan for it and you have the same problem then of relatively rare events and being there in the right place with the right equipment that’s calibrated to do it so that becomes the challenge. I’ll let Dave take the radar question.

David Sills: Well, both Greg and I are on a committee that’s developing a new EF scale and things like photogrammetry and the use of radar measurements are inputs to this committee, and they’re being considered as ways to characterize tornadoes. So, they’re not part of the EF scale that’s used in Canada or the U.S. right now, but in the future, they may form some part of how we characterize tornadoes.

Sarah Dawson: Are you doing any research on non-tornadic severe thunderstorm winds? I understand that one of your students is working on downburst microburst climatology.

Greg Kopp: Yes. That’s the short answer, we are looking at all of these thunderstorm-based storms and damage and trying to understand those downbursts are quite common and they have a very different damage footprint than tornadoes and we’re also looking at that and trying to understand those kind of wind storms as well. The ultimate goal is to be able to reduce damage, mitigate losses from these storms. In the U.S., thunderstorm-based damage is on the same order of magnitude, on average, every year as hurricanes. And hurricanes get designed for but these other storms don’t, and so we’re trying to change that and getting as much information as we can is important to that.

Sarah Dawson: It was interesting that you mentioned the tornado in North Middlesex in 1953. One of our viewers, their father often told them stories of the citizen rescue and recovery he was involved in after that event. There were three fatalities on his farm. And at that time, there would have been no emergency management system set up. The question is, do you coordinate or advise with emergency management with what you are learning since this forming this project?

Greg Kopp: Yes. We trying to work with as many partners as we can to disseminate what we’re learning from it and emergency managers are one group that we’re working actively with and building relationships with to help transmit the information that we’re learning.

Sarah Dawson: If you’re on the highway, when the tornado warning alert comes, and you can’t get off the highway, do you stay in your car, do you go into a ditch, do you not go to an underpass? What’s the safest thing to do?

David Sills: Definitely don’t go under the underpass. There’s been experiences in the past in the United States where people have taken shelter in the underpass and the wind from the tornado actually accelerates as it goes through the underpass, so you’re actually getting stronger winds there.

I think the official advice still might be to get out of your car and get into a ditch. It’s interesting because we see a lot of pictures where a lot of debris ends up in the ditches so, it’s hard to say that’s a safe place to be. A car is actually not a bad place to be, as long as the tornado is not strong enough to take your car and fling it into the air. Really, the percentage of tornadoes that can do that is very low, but you have to be cognizant that any debris that comes your way is going to go through those windows. So, being in a car, you’re pretty safe from lightning because the car acts as a Faraday cage and you don’t have to worry about the lightning so much. And if you stay down low in the car, you don’t have to worry about the debris as much either. The windows might get smashed out and you’ll get glass on you or something like that but as long as you keep low in the car and out of the way of debris, then you’re fairly safe.

So I think that would work for a large percentage of the time but if it’s a huge tornado that you see coming, a car is not going to be a place you want to be, probably you will want to get as low as possible, that’s why they suggest a ditch because you don’t want the debris hitting you so if you get into a ditch the debris will go over you. And I would suggest that for the very big tornadoes that you might see coming towards you.

Sarah Dawson: Why do cities not seem to get hit? It seems like a lot of tornadoes that we hear about are in more rural areas or is that just our perception?

David Sills: I think it is [our perception]. Cities occupy a very small amount of land compared to rural areas and there’s lots of examples of tornadoes going right through downtown areas. Nashville, Tennessee, got hit by a big tornado, Oklahoma City too. In Canada, in 2018, we had a tornado that went through Ottawa. So, there’s nothing to prevent a tornado from going through a big city, they can get disrupted a bit by very large buildings, say in downtown Toronto or something like that. But for the most part, there’s nothing in a city that’s going to stop a tornado and the occurrence rate should be about the same.

Sarah Dawson: For all the students that are out there, they would like to know what kind of opportunities within this project are there to get involved?

Greg Kopp: Well, we’re still working on that. We have several interns with us this summer, and it’s something that Dave and I started realizing last summer because we started getting contacted by high school students and others who are interested and so we’re trying to figure out how to incorporate more people into the work.

As we get more data, I think there’s going to be more opportunities for that, especially for high school students. If you’re interested in computer programming and machine learning and those kind of things, we’ll have lots of opportunities for that kind of analysis on our team.

Sarah Dawson: I think that what we’re learning from some of these questions is that there’s so much interest in your field of research, and it’s a nice merge between something really scientific and something that is just captivating to the average, everyday person.

Thank you so much for all your research, and your hard work and your willingness to come and meet with us today to share what you’re working on.

Greg Kopp: Thanks, Sarah.

David Sills: Thanks. Bye.