Why does a tornado sound like a freight train?
Summary
The rumble of a tornado reflects a jumble of frequencies produced by winds whipping around inside a furiously spinning air column at different speeds and colliding with all manner of detritus.
When a tornado tears across the landscape, shredding roads, pulverizing buildings and carrying away whatever else is in its path, the roar of the storm is often compared with the sound of a freight train.
“It was pretty loud," said Mark Monis, 29 years old, a resident of Gaithersburg, Md., who captured video from his vehicle on Maryland Route 355 as a tornado howled through the area on June 5. “It did sound like a freight train rolling by."
The rumble of a tornado reflects a jumble of frequencies produced by winds whipping around inside a furiously spinning air column at different speeds—sometimes topping 200 miles an hour—and colliding with detritus of all shapes and sizes. Twisters are usually born in massive rotating thunderstorms, and thunder and hail can also contribute to the racket.
“It’s a really loud white noise," said Harold Brooks, a research meteorologist at the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory in Norman, Okla.
More than 1,170 tornadoes have been reported this year, though final counts are usually lower after the National Weather Service verifies reports. From 1990-2022, there were, on average, 1,223 confirmed tornado reports a year.
Most of the 1,000-plus tornadoes the U.S. sees annually turn up in central states such as Texas, Oklahoma and Kansas. No one can predict exactly where one will appear, but scientists have identified weather patterns gleaned from temperature, wind and moisture measurements that often yield potent twisters.
Meteorologists look for tornadoes using radar and a network of volunteer storm spotters. To assess the threat of a brewing storm, they send radar pulses into the tempest that are reflected back within seconds with information about rainfall, hail and wind speeds.
But one day, a roar that the human ear can’t detect could also prove useful.
Brian Elbing, a mechanical engineer at Oklahoma State University, is among a handful of researchers who record inaudible “infrasounds" from tornado-producing storms. These low frequencies have been observed when conditions are ripe for a twister to form and can be captured at a distance, raising hopes that one day they could be used for tornado detection.
“If you’re close enough to see it," he said, “you don’t have much warning."
Write to Nidhi Subbaraman at nidhi.subbaraman@wsj.com
