Ten myths about tornadoes

The devastating tornado that hit Joplin, Mo., on Sunday has many people asking how they can protect themselves from these deadly storms. Here are 10 misconceptions about tornadoes you should know.

1. People should take shelter under overpasses or bridges.

In fact, this puts you at great risk for impalement by a flying object, and the winds of a tornado are plenty strong enough to suck you out from underneath open structures.

2. Tornadoes avoid big cities.

Tornadoes seem to avoid big cities because the ratio of open land to cities is so high. As the National Oceanic and Atmospheric Administration (NOAA) points out on their website, downtown Dallas constitutes about three square miles, while Dallas County is about 900 square miles. Thus, the odds of a tornado in Dallas County touching down in the heart of the city is 1 in 300.

3. Tornadoes always travel northeast.

It's true that many tornadoes move in that general direction, but tornadoes are notorious for abruptly changing direction, moving in some other direction when encountering cold air, and even backtracking and hitting an area again. Tornadoes have been reported moving southwest their entire duration--exactly opposite of the rule.

4. Wide tornadoes are stronger than narrow tornadoes.

Any shape of tornado, including thin ropey funnels, can register as an F5 tornado, the strongest classification on the Fujita scale of tornado damage.

5. You should open the windows if a tornado is coming.

A tornado will blow out the windows and do whatever damage it will do regardless of whether you open them. Houses do not explode due to a dramatic change in air pressure in a tornado--the drop in air pressure in a tornado is no more than 10 percent.

6. Stay in your car.

Only if you are driving away from the tornado. A car sitting in the path of a tornado, or overtaken by one, is likely to be picked up by the funnel cloud and destroyed.

7. If a tornado doesn't touch the ground, it won't do damage.

The visible condensation funnel is not what causes tornado damage; the high winds rotating around it does. If swirling debris is visible below a funnel cloud, the tornado is very dangerous.

8. Tornadoes don't form in winter.

Tell that to the families of the 19 people who died in January and February of 2008, in Arkansas, Missouri, Indiana, Louisiana, Tennessee, Kentucky and Alabama.

9. Tornadoes can't cross rivers or other large bodies of water.

The Tri-State Tornado of 1925, the deadliest on record with 695 deaths, crossed the Mississippi River, to name one of many examples. NOAA asserts, Almost every major river east of the Rockies has been crossed by a significant tornado.

10. The safest part of a basement is the southwest corner.

The theory is that since many tornadoes travel northeasterly, the resulting damage will fall to the northeast. In reality, the soundness and design of the structure that you are in determines which area is the safest. The winds of a tornado are rotating, which means wind will be pushing in any direction in a tornado, dependent upon which portion of the tornado you encounter.