Tornadoes are big funnel-shaped clouds that can rip through a community and leave a wake of destruction. They can form in seconds, change direction in a heartbeat, and their devastation can last a lifetime. Exactly how and why tornadoes occur is still a bit of a mystery, but an indication that one is forming is a wall cloud. Fast-moving winds roll air below into a horizontal vortex above an opposing surface. Similar to a spinning to warmed by the Sun, buoyant air near the ground begins to lift a section of the horizontal vortex into a vertical position.
The vortex extends toward the ground as it picks up speed. Anything in its path can be ripped apart or thrown in the air. Upper-level winds tilt the rotating updraft, called a mesocyclone. This allows a storm to keep growing as warm air is sucked into the storm, away from the cool downdraft. The vortex spins like a top, sometimes up to 300 miles per hour. While some tornadoes move slowly, others can travel over the ground at speeds of over 110 miles per hour.
The widest tornado ever recorded, the May 2013 El Reno tornado in Oklahoma, was 2.6 miles across—that’s wider than Manhattan. Research has allowed us to identify the essential ingredients needed for twisters to form in the U.S.: warm, moist air typically from the Gulf of Mexico, cool air typically from Canada, and dry air typically from the Rockies. When these air masses collide, they create the perfect conditions for a tornado.
Nearly three-quarters of the world’s tornadoes occur in the United States, and the peak season is between May and June. A majority touch down in Tornado Alley, a section of the central United States, but tornadoes have been recorded in all 50 states and on every continent except Antarctica.
Tornadoes are very dangerous, and you should never underestimate their power. The average time between a tornado warning and a strike is estimated at a mere 13 minutes, giving residents little time to seek shelter. On average, tornadoes kill 60 people every year in the United States.
The deadliest tornado in history was not in the United States but a tornado that ripped through Bangladesh in 1989, killing an estimated 1,300 people. We measure the amount of damage to land and property using the EF scale, which ranks tornadoes on six different levels—from zero, a heavy breeze that can uproot crops, to level five, enough wind to pick up a house.
It’s the desire to better understand them that sends scientists into the field year after year in search of answers that can hopefully save lives while putting theirs at risk.
