Why Are Tornadoes so Dangerous?

When tornadoes touch down, people run for cover. They crouch in bathtubs or hide in basements and then listen as the storm nears. Survivors have described terrifying rumbles that shake the house and banging noises against the roof. They hear glass shatter, trees plummet to the ground, and, as one survivor recalled, an eerie groaning sound when his house strained from the force of the wind.  

Sometimes, shelters aren’t enough to protect people from deadly tornadoes. In a typical year, about 1,000 reported tornadoes in the U.S. result in 80 fatalities and 1,500 injuries. These storms can happen anywhere in the country but typically occur in the Great Plains, Midwest, South and Southeast.

Meteorologists have become increasingly skilled at predicting deadly storms and have been able to forewarn about 87 percent of them. Scientists are learning more about what makes tornadoes deadly and how people can protect themselves. 

In the U.S., tornadoes are one of our most deadly natural disasters. Tornadoes are swirling air columns stretching from a cumuliform cloud to the ground. They typically occur within supercell thunderstorms, and they have the potential to be deadly because of the intense energy that is concentrated within a small area.

Since 2007, meteorologists have used the Enhanced Fujita Scale (EF Scale) to rate the strength of these storms. The lowest rating, EF 1, has wind gusts between 65 to 85 miles per hour. The highest rating, EF 5, has wind gusts of more than 200 miles per hour.

These high winds have the power to knock down trees, lift vehicles and move houses. Roofs cave, walls collapse and floors buckle. Everyday objects become deadly projectiles that can travel for hundreds of miles.

 In a 2013 study in the Bulletin of American Meteorological Society, researchers examined data from almost 1,000 objects blown away during a tornado outbreak. The furthest objects were found more than 200 miles away.

The outbreak happened on April 27, 2011, when 120 storms struck Alabama and parts of Tennessee and Georgia. Five of the tornadoes were rated EF 5. The researchers examined objects placed on a lost and found Facebook page intended to reunite people with their missing belongings. One windbreaker was blown more than 60 miles away in the storm. The furthest found object, a photograph, was found more than 200 miles from home.

Based on these results, the study’s authors suggested that items found the furthest away were carried higher in the tornado before the storm broke apart and the object plummeted to the ground.

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The 2011 storm was one of the deadliest in recent history and killed more than 300 people. Researchers have compared it to a storm in April 1974 that produced a similar amount of tornadoes and fatalities.

But they note there was an alarming difference between the 1974 and 2011 storms. The 1974 storm stretched all the way from Alabama up to Canada. Six storms rated as EF 5 were spread across multiple states spanning from Alabama to Ohio. The 2011 storm, in contrast, was more concentrated. Most of the tornadoes hit Alabama, and the EF 5 storms struck a smaller area.

Storms are becoming more concentrated, and scientists have also observed an increase in the number of tornadoes occurring on the same day.

Although the annual number of days with tornadoes has decreased in the past 50 years, the number of tornadoes has remained consistent overall. This is because they have started clustering, and multiple storms are happening on the same day.

For example, on March 31, 2023, a “tornado outbreak” brought 30 confirmed tornadoes that tore through Iowa and Illinois and injured 11 people. The strongest of the storms had sustained winds of 170 miles per hour.

Scientists aren’t sure if the change is related to climate change, but they are more confident in their increasing accuracy in predicting deadly storms and sending out warnings in advance. Problematically, many people live, work and shop in structures that offer little protection in high winds.

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Most deadly tornadoes in the U.S. occurred in the nineteenth and early twentieth century before meteorologists had access to sophisticated detection equipment. Even though sirens now blare and social media alerts ping, tornadoes still claim lives every year.

Scientists find there are multiple reasons for the continuing fatalities. One reason is a population increase in tornado-prone areas, and many people live in homes that aren’t designed with storm safety in mind.

For example, mobile homes and prefabricated homes are not anchored to the ground. Strong gusts of wind can flip these homes on their sides or even lift them off the ground. About 79 percent of these fatalities since 1985 have been people who lived in mobile or prefabricated homes.

Researchers who study deadly tornadoes argue that communities with mobile or prefabricated homes should have a public safety shelter that is easy for residents to reach. Homes without a basement should have an interior safe room where residents can ride out the storm. Similarly, businesses should also have safe rooms for employees, shoppers or guests seeking shelter.

Sheltering shoppers in a strip mall can likely be accomplished with safe rooms, but researchers stress about large gatherings in outdoor venues like stadiums. Motor speedways, for example, are designed to be open-aired venues that attract tens of thousands of visitors. Many aren’t designed with subterranean tunnels where the public can take cover. Knowing this, researchers call for continuing advancement in storm prediction and alerts so that venues can cancel in advance or fans can heed the warning and stay home.

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