Science | April 26, 2024

Ten Amazing Facts About Tornadoes, Explained

To prepare you for the movie “Twisters,” we’ve compiled some jaw-dropping details about the powerful phenomenon

A multi-vortex tornado touches down on the town of Patricia, Texas. John Finney Photography via Getty Images

Staff Contributor

As looming thunderstorm clouds spit out baseball-sized hail and torrential rain, a narrow whirlwind of air stretches its way toward the ground, signaling the arrival of one of nature’s most violent phenomena: a tornado.

Also known as twisters, these violent cyclones can reach wind speeds of 300 miles per hour and blaze a path of destruction that can last from mere seconds to several hours. While most people flee or take shelter at the sight of these alarming conditions, others dive headfirst into them. Storm chasers, people who get dangerously close to extreme weather events, sometimes for scientific research, jump at the chance to pursue the ever-unpredictable tornado.

The 1996 disaster classic Twister follows a group of these daring storm chasers, a university professor and her team of students who rush toward an outbreak of severe twisters sweeping Oklahoma. Their goal: deploy a revolutionary weather alert device, aptly named “Dorothy,” within the heart of multiple tornado systems to track and possibly tame the forces of nature. After a series of disastrous attempts to deploy their invention within multiple cyclones, a final, massive tornado rips through the area. In the nick of time, the team successfully sets up their device in the twister’s center and collects crucial data.

The highly awaited sequel Twisters sees the continuation of this research nearly two decades later, with a new generation of storm chasers and technology. The story’s hesitant protagonist Kate Cooper, played by Daisy Edgar-Jones, joins forces with adrenaline junkie Tyler Owens, played by Glen Powell, as twin twisters ravage the plains of central Oklahoma. The pair races against a rival team and devastating weather conditions to conduct groundbreaking analysis. Though the film is fictionalized, its overarching circumstances—the treacherous nature of twisters and the difficulty of predicting their arrival—ring true.

In anticipation of the July 19 release of Twisters, we contacted three scientists to unravel some of the secrets wrapped within these catastrophic cyclones. Here are a few of the coolest finds we uncovered.

Supercell thunderstorms are responsible for creating tornadoes

Tornadoes are born within supercell thunderstorms, an anvil-shaped cloud with a rotating updraft called a mesocyclone. As an extremely rare weather event, only one in thousands of storms yields a supercell thunderstorm. One in five or six supercells, though, produces a tornado.

“To get a thunderstorm, we have to have an unstable atmosphere, and generally, for a tornado, we need the thunderstorms to rotate,” says William Gallus, a meteorologist at Iowa State University. “That happens if we have wind shear, which means that the wind speed and wind directions are changing as you go up.”

Warm air rises, cold air falls, rough winds whip within the storm system, and an updraft occurs. If this rotating updraft descends toward the ground, lowering itself below the storm, a tornado can emerge from the chaos.

The tornado forms as the mesocyclone accelerates from the bottom up—and the feature intensifies its rotation, in a way similar to an ice skater who pulls her arms into her body to spin faster, says Jana Houser, a supercell thunderstorm and tornado radar analysis expert at Ohio State University.

The strongest winds of the tornado are closest to the ground

Tornado in Nebraska — A tornado moves across Nebraska. Mike Hollingshead via Getty Images

In the atmosphere, the winds get stronger the higher up you go. Tornadoes reverse these conditions, with their strongest winds appearing at the lowest points. This powerful rotation starts at the ground and then floats its way upward to converge into the visible funnel cloud.

“This process happens very quickly,” says Houser, who, alongside her team and National Geographic cameras, captured the very tornadoes set to appear as background footage in the upcoming film Twisters. “In under a minute, you can go from a weak rotation to, all of a sudden, a full tornado.”

According to Gallus, computer models of tornadoes have shown that the strongest winds could lie just 15 feet above the ground—their most brutal region lining up with the height of homes and buildings.

“That’s pretty unfortunate for all of us who live on Earth, because that means that in a tornado, unlike any other weather system, the very worst winds are impacting buildings, people and trees down near the ground,” says Gallus.

Tornadoes can form anywhere, anytime

Tornado Alley Map — Diagram of Tornado Alley Dan Craggs via Wikimedia Commons under CC By-SA 3.0

Most tornadoes are formed in the Great Plains of the United States, in an area deemed “Tornado Alley.” Flat terrain combined with unstable conditions—warm, moist air from the Gulf of Mexico collides with dry winds drifting in from the Rocky Mountains—provides the ideal breeding ground for twisters to spawn. But tornadoes can happen almost anywhere. They have been reported in all 50 states and all continents except Antarctica, and they’ve struck major urban areas, such as Dallas, Miami and Minneapolis.

But cyclones don’t follow any sort of pattern or path, contrary to popular misconceptions. “It doesn’t matter if you’re in a downtown part of the city, in a hilly area or even a mountainous area,” says Houser. She adds that some terrain may reduce or increase the probability of tornadoes, but complete protection from the twisters can’t be guaranteed.

Similarly, while peak tornado season ranges from May to July depending on location, tornadoes can hit at any month and any time, both day and night.

Tornadoes have uniquely powerful upward motion

In most weather phenomena, the most aggressive winds blow horizontally, directing their potency outward toward the north, south, east and west, rather than upward and downward. Tornadoes defy these expectations. Things resting in the tornado’s path—the roofs of homes, cars, animals—can be suddenly whisked straight up and into the whirl of debris, victim to the sheer power of the tornado’s upward winds. According to Gallus, the strength of a tornado’s upward motion is comparable to the speed at which it moves along terrain, with 100- or 200-mile-an-hour winds shooting up toward the sky.

“That’s why the damage that a tornado does to buildings is very different than if you have the exact same mile-per-hour wind from just a thunderstorm,” says Gallus. “It’s also why you hear these stories of people or things getting picked up and seeming to levitate or fly up into the air—it’s because the tornado has such strong upward motion.”

The air pressure inside a tornado can cause just as much damage as the wind itself

Tornado Rubble — Rubble left by a tornado Greg Vote via Getty Images

When visiting the site of a Missouri hospital ravaged by a tornado, Gallus recalls, a nurse he spoke with had to tilt her head a certain direction to hear. Due to the intense air pressure change caused by the tornado, her eardrum ruptured. The air pressure in the middle of a tornado can drop suddenly and strongly, as if you were riding on a plane flying up into the air extremely fast. Many people near tornadoes have reported their ears “popping” during the phenomenon. “That change in pressure is almost like nature’s way of giving you a very last warning by having your head experience this strange rapid adjustment and popping going on in your head,” says Gallus.

The change in air pressure can also create an additional force on buildings that, along with the strong winds, can intensify and quicken their destruction.

Terrain can change a tornado’s behavior

Tornado Over Great Plains — A twister moves over the Great Plains. Laura Hedien via Getty Images

Researchers have a difficult time predicting when a tornado will form—and where it will go. Changing winds and differing terrain can make it hard for meteorologists chart the exact path of a twister.

“Tornadoes are incredibly susceptible to very small nuances in the land cover, in the environment, in the storm itself, and it’s very difficult, I would say impossible, to account for every single factor that could possibly go into changing what a tornado is doing,” says Houser. “They defy generalization.”

While predicating a storm is hard, meteorologists say that some features of terrain may enhance the conditions needed for a twister to form. For example, sprawling urban areas can affect thunderstorms, which, in turn, can affect tornadoes. Since cities have more precipitation on their downwind side because of the way water systems interact with urban structures, they produce more rain and more hail, and can be warmer, helping set up an environment that’s more likely for a tornado to form.

“Sometimes urban areas are warmer than rural areas due to the urban heat island. What happens if a tornado goes over a warmer city?” says Jason Naylor, an atmospheric scientist at the University of Louisville. “It looks like the urban heat island could potentially enhance the low-level updrafts in the storm and may help instigate tornadoes in a theoretical way.”

Tornadoes usually rotate counterclockwise, but they can switch directions

Rope Tornado — A rope tornado descends upon La Grange, Wyoming. National Oceanic and Atmospheric Administration / Vortex II

In the Northern Hemisphere, about 98 percent of tornadoes spin counterclockwise, which meteorologists label as cyclonical. However, a clockwise-swirling tornado is not out of the question—just much less common.

The counterclockwise motion of most tornadoes has long been attributed to the Coriolis effect, the force caused by the Earth’s rotation. But, according to Houser, this is merely a myth. Tornadoes exist on “too small a space scale and time scale for the Coriolis force to affect it,” she says. Rather, the counterclockwise motion results from how vertical winds change in speed and height within the storm.

Meteorologists call clockwise tornadoes anti-cyclonic. “You get an anti-cyclonic tornado when you have a very strong surge of air within the storm,” says Houser.

Storms can produce more than one tornado at a time

Two Tornadoes — Twin tornadoes converge on Wisner, Nebraska. Ethan Schisler / National Oceanic and Atmospheric Administration

Twisters sees two groups of storm chasers unite as two different tornadoes converge over a small town in central Ohio. This event isn’t just movie magic: The same storm system can really eject multiple tornadoes at once. As winds change, the storm itself can begin to form a new tornado in a slightly different location from the original tornado—with the fledgling rotating updraft gaining power as the other twister slowly dies down. Or, if the original tornado is particularly violent, the level of agitation can churn out smaller whirlwinds that extend toward the ground.

And Houser says that other freak circumstances, such as extremely strong rotation along the edges of a storm, can also produce multiple tornadoes. A clockwise and counterclockwise tornado can even appear in the same storm system.

Tornadoes themselves can’t be forecast—only the conditions that produce them can

Radar of Thunderstorms — Radar detection of a hook echo in a supercell thunderstorm National Oceanic and Atmospheric Administration

The 1996 film Twister and its 2024 companion Twisters center around the same key issue: the frustrating impossibility of forecasting tornadoes. “We don’t even really try to forecast exactly when and where a tornado would hit, because we simply cannot do that ahead of time,” says Gallus.

Warnings for tornadoes are only issued when a twister is already forming and has been sighted—or indicated by weather radar—and the alerts cover an area that may be impacted.

Scientists are able to predict, however, the conditions favorable for supporting thunderstorms that spin and would be more likely to produce tornadoes. Up to a couple of hours ahead of time, when increased weather severity is detected, local television and radio news stations issue a tornado watch.

But a tornado’s intensity can’t be determined until after its wake. Scientists determine a tornado’s level of destruction by using the Enhanced Fujita Scale. The scale assesses the damage a tornado does to trees, buildings and homes. Scientists then use that information to calculate its probable wind speed. The rating system ranges from F0, the weakest cyclone, to F5, a vicious, deadly tornado, which a character in Twister deems the “finger of God.”

Climate change is affecting tornadoes

Tornado Alley is moving eastward. In the past decade, twisters have been inching their way into the Midwest and hitting states such as Missouri in record-breaking severity. Meteorologists attribute this shift to climate change.

“Now, with climate change, places that were normally too cold in the winter are finding themselves with days warm enough that you’re starting to see tornadoes at times of year, parts of the country, where they didn’t used to happen,” says Gallus.

This is caused by climate change’s impact on weather. Gallus says that climate change is making conditions warmer and more humid near the ground, which is increasing the level of instability that leads to stronger, tornado-producing storms.

According to Gallus, we may see more days that meteorologists call tornado outbreak days, where five to ten tornadoes crop up. But climate change could also decrease the frequency of days where one or two tornadoes crop up. Essentially, the number of tornadoes could be concentrated on fewer days.

“We can’t say that tornadoes are going to become stronger. We can’t say that we’re going to have less,” says Gallus. “But what we do know is, because of how the temperature is changing, we are going to start finding them in weird times of the year and places where it always used to be too cold to have a tornado.”