Imagine driving down the interstate as the sky turns dark. You come over a hill and see a tornado ahead of you. What do you do?
- Highway overpasses offer no shelter from flying debris. The wind in a tornado isn't what injures and kills people, it's the debris moving in the tornado. A weaker tornado can still produce winds in excess of 100 m.p.h.
- A tornado's wind speed increases with height. Climbing above ground to situate yourself under an overpass actually puts you at greater risk for fast-moving debris.
- As a tornado comes in contact with a bridge overpass, the wind is channeled around the contoured land mass near the approaches to the bridge. This "wind tunnel effect" can increase the velocity of wind under the overpass.
- Typically, the underside of highway overpasses are free of anything to hold onto. Anyone subjected to even a weak tornado's wind could be sent flying. It's a poor choice, even as a last resort.
- Tornadoes don't produce wind moving in a straight line. A swirling nature of a tornado's vortex means anyone under an overpass will be subjected to a 180-degree change in the wind direction...all in a matter of a few seconds.
Back in 1991, a group of people escaped injury by hiding under a bridge overpass and it was caught on camera. Unfortunately, this led people to believe they were doing the right thing.
So where should you go during a tornado when no safe shelter is present? Looking back at #2, you can start think about places that are as low as possible. Underneath concrete tubes/culverts that go under the highway are the best places if you're away from a reinforced building. Staying in your vehicle is not a safe option, even with some arguments in the past few years suggesting it so.
-Meteorologist Eric Sorensen