It’s been a bad tornado season across the United States. Over the last few weeks, multiple tornadoes have caused deaths and tremendous property damage in several states.
On Sunday, a massive funnel cloud was spotted touching down near Bennett, Colorado. The tornado tore through central Colorado, avoiding the Denver Metro area but damaging over 20 homes in its path.
According to a report from the National Weather Service Denver/Boulder office, at least four tornadoes touched down on Sunday. Two of the four were classified as “2” on the Enhanced Fujita (EF) scale, with winds around 125 miles per hour.
Wyoming is more tornado-proof than tornado-prone, but the tornado that touched down in Colorado should serve as a potent reminder of a potentially dangerous season ahead. Funnel clouds from the same storm were spotted over Cheyenne on Sunday.
“We’ve seen tornadoes in Grand Teton National Park,” said Cowboy State Daily meteorologist Don Day. “This year has certainly been more active for tornadoes, and this is the time of year when we should expect more tornadoes in Wyoming.”
Where There’s Thunder
Tornadoes are columns of air that violently swirl as weather systems collide in the atmosphere. But they don’t form out of thin air.
“You need a thunderstorm for a tornado,” Day said. “To get a strong thunderstorm that generates a large tornado, you need moisture. As the seasons change, you get colliding air masses that create opportunities for strong thunderstorms that lead to other severe weather.
Tornadoes form at the base of cumulonimbus clouds. The swirling winds within the cloud, which can reach over 200 mph in worst-case scenarios, extend from the base of the cloud to the ground and can be powerful enough to lift and hurl vehicles, structures, and people.
Day said this has been a particularly good year for tornadoes, which is bad news for everyone living in tornado-prone areas. The United States has more tornadoes than any other place in the world, and dozens have been reported over the last month.
“If you were to graph the number of tornadoes year to year, you would see that some years are bigger than others,” he said. “This year has been a more active one.”
Wyoming’s Tornado Alley
When is Wyoming’s tornado season? From now until the end of summer, basically.
Wyoming isn’t as tornado-prone as other states, but that doesn’t mean it’s immune to these destructive storms. According to Day, historical data suggests our season is just starting.
“We could have tornado activity from mid-May through September,” he said. “My experience is that most of them occur late May through mid-August, so that's our peak season.”
Day said tornadoes are more likely to touch down in eastern Wyoming than anywhere else in the Cowboy State. Wyoming isn’t officially within “Tornado Alley,” which stretches throughout the Great Plains from South Dakota to Texas, but it does border several states that are.
“We tend to see the highest frequency of tornado activity in the counties that border Colorado, Nebraska, and South Dakota,” Day said. “Goshen, Platte, and Niobrara Counties are where we see the most activity, along with eastern Laramie County and southern Campbell County.”
These areas are more tornado-prone because of the topography. Eastern Wyoming is mostly flat, open prairie where it’s easier for the funnel clouds to form and touch down during severe thunderstorms.
Western Wyoming, with its complex topography, has historically fewer tornadoes. Day said the mountainous terrain serves as a buffer that makes it harder for colliding weather systems to form funnels.
“The wind flow in a developing thunderstorm pattern is how you get tornadoes,” he said. “If you have very complex terrain, mountains and ridges that kind of interrupts the ability for a tornado to form.”
Also, tornadoes need moisture and high humidity to form. While it’s dangerously dry in eastern Wyoming, the plains are still more moisture-rich than the mountains of western Wyoming.
“The open prairie and moisture-rich areas of the eastern plains make it a much more suitable area for tornadoes than the Red Desert, Rock Springs, or Green River,” Day said. “A lot of storm chasers visit Wyoming’s far eastern counties during tornado season, because that’s the bullseye.”
Perfect Storm Season
Day said the frequency of tornadoes this year should keep Wyomingites on their guard. Tornadoes require warmth and moisture to form during severe thunderstorms, but that doesn’t mean the threshold is very high.
“Sunday was a rather cool day in Cheyenne, but a strong system came in that pushed us over the edge,” he said. “You need warmth and moisture to create a tornado, but that system was still enough to create tornado activity on a cool day.”
There is one other buffer of protection in Wyoming. Because the state is so sparsely populated, tornadoes have a higher chance of touching down in areas where there are few, if any, people and structures.
Nevertheless, Day cautioned that tornadoes can happen anywhere in Wyoming at this time of year. We might not see the frequency and scale of destruction as other places in the United States, but that shouldn’t negate the fear of funnels touching down in the Cowboy State.
“We can get some really strong, dangerous tornadoes, especially in the eastern counties,” he said. “We're not Oklahoma, Nebraska, Kansas, Texas or the Midwest, but we still run that risk of deadly tornadoes in Wyoming.”
