Tornado Myths
There are dozens of myths and stories about tornadoes.  Unfortunately, not having the facts and acting on bad information can have deadly consequences.  Here is a short list of popular myths about tornadoes, and the correct information (courtesy of NOAA and Wikipedia):

Using Highway Overpasses as Shelter
Myth: Highway overpasses are adequate shelter if a tornado approaches while you are on a road.

The Truth: Sensational footage taken by a television crew hiding from a tornado under an overpass during the 1991 Andover, Kansas Tornado Outbreak helped to convince some that bridges are good shelters when a tornado is nearby. The members of the television crew (and several other travelers) survived by huddling high underneath the bridge and bracing themselves against support columns while a weak tornado appeared to pass directly over the bridge.

In reality, when directly hit by tornadoes, the confined spaces beneath overpasses increase the speed of the winds due to the Venturi effect, and thus make them potentially less safe (somewhat like being in a windtunnel). In the case of the Andover tornado footage, it was discovered that the tornado did not pass directly over the bridge, but instead over the ground slightly south of the bridge and camera crew, exposing them to much weaker winds.

Tornado Behavior Myth: I don’t have to worry about skinny tornadoes, only the fat or big ones are strong. 

The Truth: A lethal myth. In the first place all tornadoes are dangerous, and should never be dissmissed as “not powerful”. Secondly, although large tornadoes are generally more powerful, this is not always the case. There have been many instances where “classic” funnels (normal size) or even skinny funnels were deadly F-4 or F-5 tornadoes, where-as a large 1/2 mile wide “wedge” tornado (which make up a lot of F-4 or F-5′s) might be an F-3. So the width of a tornado is not a good indicator of how powerful it is, and all tornadoes should be taken very seriously.

Myth: Tornadoes don’t happen at night. 

The Truth: Not only is this a fatal myth, but tornadoes at night are among the most dangerous of all, since most people are asleep and don’t hear the warnings when they happen. It is true that the vast majority of tornadoes happen in the daytime, generally in the late afternoon during the high heating of the day, but tornadoes can and do happen at anytime of the day or night.

Myth: Twisters are attracted to mobile homes and/or trailer parks. 

The Truth: Trailer parks consist of low-cost mobile homes with less structural integrity than traditional houses. A weak storm that leaves little damage to well-built structures might devastate a trailer park. Mobile homes do not attract tornadoes; they are just more susceptible to damage from them.

Myth: Tornadoes cannot form near rivers or cross them, Tornadoes cannot follow terrain into steep valleys, Tornadoes cannot travel over steep hills or mountains.  Some places like cities and downtown areas are safe from tornadoes.

The Truth: Tornadoes can, do, and have struck all of the above.  Among the many tornadoes that have crossed rivers is the most deadly tornado in US History: the Tri-State Tornado, which crossed the Mississippi River and strengthened into an F5.  All of the tornadoes from the Super Outbreak that struck in NC struck in the mountains, including an F4 near Murphy, NC that crossed a 3,000 ft. ridge.  Finally, there have been many tornadoes that struck downtown areas, including the F5 that devastated Moore, OK in 1999.

Home Safety in a Tornado Myth: Most tornado damage is due to the low pressure in the tornado causing the house to explode. Opening your windows or doors while a tornado approaches will equalize atmospheric pressure and help prevent property damage. 

The Truth: Since windows are typically the most fragile external feature of a house, they are in more danger from flying debris. Opening them during an active tornado wastes time and effort that could be spent on other, more useful protective measures. Homes do not “explode” when hit by a tornado, though it often appears so. Commonly, a tornado will break the windows first, allowing strong winds to enter the home. These winds may then push on the underside of the roof upwards, blowing it off. Without the roof, the walls lose structural support and will often fall outwards. Observing the wreckage after the collapse may give the impression the house was pushed apart from the inside. Other ways a house may be perceived to have been “blown apart” is from the winds pushing up against the roof where it meets the walls, ripping the roof off, and causing the walls to collapse.

 Flying debris or wind from a tornado will break the windows anyway, so opening them only wastes valuable time and is even counterproductive to the soundness of the structure. It is the debris and wind that breaks windows, not the difference in pressure.

As a note, this also applies to homes or structures that are hit by a hurricane. Studies from the National Hurricane Center suggest that closed containers do not explode during high wind scenarios. But rather, an opening, such as a broken window, will allow the hurricane force winds to enter a room and subsequently destroy an entire building.

Myth: During a tornado, the southwest corner of a building is the safest.

The Truth: An unfortunately fatal belief, and for a long time it was considered sound advice but without any proof of safety compared to any other parts of a building. After the increase in tornado research during the turn of the millennium, the US National Weather Service has now adopted the advice that the central-most-room on the lowest level of a structure is the safest, with centrally-located rooms in an underground level being far safer than any above-ground location. In reality, a tornado can hit any part of a building thereby making any part of the exterior subject to damage from rapidly changing winds.