Myths continue to kill! In a film entitled terrible Tuesday, about the  Wichita Falls tornado of 1979, a man was interviewed by a reporter about his  close brush with death. He had been on the highway when he realized a tornado  was coming. He parked his car and ran up underneath the overpass crossing the  highway. In the early 1990s, the television crew covering a story was on the way  back from the shoot. They saw a tornado, and when they realized it was gaining  on them, they parked the car and ran up under the overpass, where several other  people had also tried to take shelter. A small tornado was headed straight for  them, but tossed around a van before it reached them. The weak tornado passed  south of them, but both the experience and the video were very intense. This  video was seen on television programs and newscasts by literally millions of  people! 

Since that video clip aired, many people have come to assume that this is a  safe shelter, perhaps because the news crew survived. But this is a modern-day myth. Scientists and meteorologists and the  emergency management people have become very frustrated with the increasing  number of motorists who are doing this routinely. The truth is, any time you  deliberately put yourself above ground level during a tornado, you are suicidely  putting yourself in harms way. 

During the May 3, 1999 Oklahoma tornadoes, dozens of drivers pulled over on  the highway and ran up under highway overpasses. Not only did this put them at  risk, but they put many other motorists at risk by blocking the roads in the  area of the overpass. An informal survey of storm chasers showed that 9 out of  10 storm chasers felt that overpasses were extremely dangerous places to be  during a tornado. 

Scientists at the SPC and NSSL knew that it was simply a matter of time until  someone was hurt or killed because they chose to climb up underneath an  overpass. And on May 4th, that prediction proved to be true. A woman and her  child climbed up to shelter beneath the overpass, with several other people, and  the intense winds caught her in their grasp. She was carried a half a mile to  her death. Her child sustained slight injuries. It is regrettable that this myth  could not have been dispelled before someone paid the price with their life. An  excellent explanation of why this is unsafe is at the Southern  Region NWS site.

Myth or Misconception #4 .... Opening  windows to equalize air pressure will save a roof, or even a home, from  destruction by a tornado.

The idea that moving one thin pane of glass is going to protect a roof or  house from one of the most violent natural forces on the planet has a certain  absurdity about it. It is probably born of wishful thinking and faulty logic,  stemming from the need to do something .... anything. In reality, opening  windows is a dangerous and useless waste of time, and could actually be harmful  to the house. 

To get to the very center of a mature tornado (where the pressure may be low  enough to cause some explosive effects), the windows would have to endure  100-200 mph winds in the walls of the vortex. Those winds would be laden with  boards, stones, cars, trees, telephone poles, and the neighbor's roof shingles  as well as wind pressure of more than 100 pounds per square foot. This barrage  would blow more than enough ventilation holes in the building to allow any  pressure difference to be equalized. 

Even with the windows closed, most houses and commercial buildings have  enough openings to vent the pressure difference in the time that it takes for a  tornado to pass. The engineering team at Texas Tech's Institute for Disaster  Research (Minor et al., 1977) point out that the pressure drop inside a tornado  with 260 mph winds is only about 10%, or just 1.4 pounds per square inch. Most  buildings can vent this difference through its normal openings in about three  seconds. That is sufficient time even if the tornado is moving forward at a very  rapid 60 mph. In the real world, the discussion is pointless. That violent a  tornado would totally blow apart a house before the central low pressure ever  arrived. Venting of air to relieve pressure would not be an issue. 

If the home owner opens the wrong window, air can rush in and exert pressure  on the structure from the inside--like blowing air into a balloon. It is  unlikely that the resident knows where the construction weak points are. In  addition, the wind fields in a passing tornado are very complex and constantly  changing. It is not possible to predict the strongest direction of attack. The  best advice from every engineer with whom the author has ever discussed this is  to leave the windows alone and get into the basement or other shelter as fast as  possible. One should not think first of the house roof, but of the impact of  one's death on one's family, or of one's self unnecessarily crippled or scarred  for life. 

I don't recall the exact origin of the "window opening" advice, but do recall  that the original advice was to open windows in both the front and the back of  the house. Theoretically, this would allow air to move through the house, and  reduce any buildup of interior pressure. Somehow, the advice was altered to  include only the windows on the north side of the house, (away from the  tornado). There is no evidence that any opening of windows ever helped to hold a  roof in place. The best advice is still to forget the windows and get to a  shelter. 
 
 

Myth or Misconception #3  .... Tornadoes never strike big cities.

This misconception has a small kernel of possible truth at its heart.  Before we get to that possible bit of truth, we first have to make a number of  things clear. When one thinks of a "big city", the image of sky scrapers and  large office or apartment buildings come to mind. In actuality, if you were to  compare the downtown where these buildings occur with the rest of the city, it  would comprise a rather small percentage of the city's area. 
Let's look at a  map:
The area that is considered "the city" and consists of tall buildings is  filled in with blue. The boundaries of the city are outlined in green. The  entire city is also surrounded by suburbs, which are outlined in purple. If you  think of the city as just the area filled in with blue, then "the city" is a  very small target. That more "cities" aren't struck by tornadoes is probably  more coincidence than anything else. There are very few "big cities" with  skyscrapers in Tornado Alley. In fact, there are only a dozen, and one of them,  St. Louis, has a long history of tornadoes in its central area. 

The  downtown areas of "big cities" have had tornadoes on occasion.  This past spring, a tornado passed through Miami, Florida before it moved out to  sea, disproving the idea that they can't form in cities.
The  St. Louis, Missouri and East St. Louis, Illinois areas have had more than their share of tornado strikes to their downtowns. The first time  was on March 8, 1871, when a tornado that did F-3 damage moved from the west  bank of the Mississippi River, across the river, to the Brooklyn-Venice area of  Illinois. Ferries and steamers were torn apart and their fragments carried as  much as 30 miles. Most of the damage was to the six railroad depots that were  destroyed. Eight of the nine deaths occurred in the railroad yards.
A tornado  struck again on May 27, 1896, killing 255 people in the two states. Touching  down on the NW edge of Tower Grove Park, the storm widened into a mile-wide,  complex combination of tornado and downburst winds. It struck the Eads Bridge,  just as the windstorm had in 1871. Seven people were killed in a building about  where the I-55 sign is on the map to the right. A photo of that building, and  another photo of the East St. Louis damage can be seen here. About 1000 people were injured as  the storm collapsed or swept away portions of houses, factories, saloons,  hospitals, mills, railroad yards, and churches. The storm was at its maximum  intensity as it crossed the Mississippi into East St. Louis, and it killed 118  people there, 35 of which were in the Vandalia railroad freight yards.
The  third time St. Louis was struck was on September 29, 1927. The tornado began at  the south edge of Webster Grove and as it passed through the middle of the city,  its path widened from 100 to 600 yards. Over 200 city blocks were torn apart,  and 72 people were killed. In Illinois, 6 people were killed when a crucible of  molten metal was overturned. Debris from the tornado was carried up to 50  miles.

In the past 40 years, the city of St. Louis and the surrounding suburbs of  St. Louis County have been hit 22 times, although none of them were in the tiny  skyscraper heart of the city. There are three possible reasons for that. First,  the central city may produce a "heat island" in which turbulent rising air  disrupts the formation of small tornadoes(keep in mind that most tornadoes are  small). The second possibility is that the "roughness" created by the  skyscrapers causes turbulence that disrupts the formation of small tornadoes.  The third, is, of course, the idea that tornadoas are rare, and the central city  is very small. So it is a matter of coincidence.

Professor Fujita of the University of Chicago suggested that the "heat  island" effect takes hold for small tornadoes when a city reaches a population  of about 1,000,000. There seems to be a lack of small tornadoes in the central  cities of Chicago, Tokyo, and London. These are the only three cities that have  been carefully studied over a long time. 

None of this applies to intense tornadoes. They are just too rare to assume  that they avoid central cities. There are thousands of small towns all across  Tornado Alley that have never been hit by an intense tornado. If you have ever  seen video of the Wichita/Andover, Kansas tornado, it should seem ridiculous to  you to think that this monster, at the bottom of an 8-mile-high rotating column,  would be bothered by the presence of a few 300-foot-tall buildings. Perhaps some  time in the next century, a central city will be in the path of a violent  tornado, and we will learn what will happen. The probability of a violent  tornado in the downtown area of any large city is about once in a thousand  years. 

It is possible that a tornado could actually intensify even more after it  forms outside of town and moves into the central city. One speculation has it  that the friction of the buildings will slow down the inflow of air into the  funnel. This would deprive the funnel of air. The pressure would drop, causing  the funnel to shrink in diameter, and spin even faster. So central city  tornadoes that began outside the city could be more damaging than average. As  you can see, there is a lot more to this than the simplistic idea that heat and  roughness keeps tornadoes away. The rarity of intense tornadoes and the fact  that St. Louis has been hit by three of them is an interesting curiosity, but  that is another puzzle for another day.

Myth or Misconception  #2 .... Some towns are "protected!"
 

Various Native American tribes perceived tornadoes in different ways. Some  saw them as a cleansing agent, sweeping away the ragged and negative things of  life. Others saw them as a form of revenge for dishonoring the Great Spirit.  Today, only the myths about the protection of towns by rivers and hills linger  in modern American culture. 
 
 

The Osage Indians, native to Kansas, Oklahoma, and Missouri passed on tornado  legends to the early settlers. One such legend has it that tornadoes will not  strike between two rivers, near the point where the rivers join. In the past 150  years, this idea may have given a false sense of security to some people who  thereby failed to take shelter. They may not have lived to help debunk the myth.  One by one, the myths that particular towns are protected have fallen by the  wayside. 
 
 

Emporia, Kansas, for instance, had sat "protected" between the Cottonwood and  Neosho Rivers, in native Osage territory, for over a century. Emporia was free  of damaging tornadoes until June 8, 1974 when a tornado killed six people and  destroyed $20,000,000 worth of property on the northwest side of town. Another  tornado did $6,000,000 in damage along the west side of Emporia on June 7, 1990.  Part of the path of the 1974 tornado was also the site of a deadly twister on  September 29, 1881, but the area was farmland then. 
 
 

The idea that one's town is "protected" is a combination of wishful thinking,  short memory, the rarity of tornadoes, and a distorted sense of "here" and  "there." Proof of protection has been offered by a very simple statement of  fact. The town has never been hit by a tornado, but 10 tornadoes have touched  down "outside" of town in the past 30 years. The occurrence information may be  fact, but the conclusion that the town must be "protected" does not logically  follow. 
 
 

That logic disregards some very basic ideas. It ignores the likely  possibility that rivers, ridges, and valleys have little or no effect on mature  tornadoes. Tornadoes have passed seemingly unaffected over mountain ridges 3,000  feet high. Dozens have crossed the Mississippi River, from Minnesota to  Louisiana. Both sides of the river, at the confluence of the Mississippi and  Missouri Rivers, near St. Louis, have seen devastating tornadoes. 

Topography may have some influence, but protection is not one of them. Weak  tornadoes may damage hilltops. But well-formed, mature tornadoes may actually  stretch themselves into valleys and intensify. During this vortex stretching,  the funnel diameter may shrink in diameter and the tornado will spin even more  rapidly. This is hardly what one would call protection for buildings in a  valley.

The belief that tornadoes don't hit "here," but always seem to hit "north of  town" or "south of the river" ignores some very simple mathematics. "Here" may  be a small town with an area of one square mile. Just "outside of town" or  "there" or "to the north" may be anywhere within visual sighting from the water  tower, perhaps 10 miles in all directions. Therefore, if the town has an area of  one square mile, then "outside of town" has an area of over 300 square miles. A  tornado touchdown is 300 times more likely "outside" of town than in-town. The  "protection" of the town does not come from hills, or a mound, or the joining of  two rivers. Tornado protection comes from the same source as our protection from  falling comets or other heavenly visitors .... that afforded by the laws of  probability .... the very low probability of rare events such as  tornadoes.
 
 

Myth or Misconception #1 .... The southwest corner of a basement  is the safest location during passage of a tornado.

The truth is that the part of the home towards the approaching tornado  (often, but not always, the southwest) is the least safe part of the basement,  not the safest. This is also true of the above-ground portion of the house. In  most tornadoes, many more homes will be shifted than will be blown completely  free of a foundation. Homes that are attacked from the southwest tend to shift  to the northeast. The unsupported part of the house may then collapse into the  basement or pull over part of the foundation, or both. Historically, the few  deaths in basements have been caused by collapsed basement walls, houses, and  chimneys, rather than by debris that was thrown into the basement from the  outside. 
 
 

For nearly a century, the published conventional wisdom was that the  southwest corner of a building, both above and below ground, afforded the best  protection. This misconception probably originated from someone's reasoning,  rather than from actual observations. They probably assumed that deadly debris  would be propelled over the southwest corner and land in the northeast corner. 

The idea that it was safe to seek shelter on the side of a house facing the  oncoming tornado dates back to at least the first book on tornadoes, the 1887  comprehensive text Tornadoes , by John Park Finley. He placed in  italic for emphasis the following remark: "Under no circumstances, whether in a  building or in a cellar, ever take a position in a northeast room, in a  northeast corner, or an east room, or against an east wall." He also recommended  removing the furniture from the west-facing room and closing all windows in the  house. This is all incorrect, deadly, and time-wasting advice. It is quite  possible that someone has died following it. While relatively few people  probably read the book when it was available, the advice was quoted in many  newspapers. It is possible that in the limited number of damage surveys that  Finley conducted personally, he came upon a grisly scene involving the northeast  portion of a poorly constructed house that had fallen over, and it strongly  influenced his thinking. 

These assumptions went essentially unchallenged until 1966, when Professor  Joseph Eagleman of the University of Kansas undertook a survey of destroyed  produced by after the Topeka tornado of June 8th. Professor Eagleman's objective  study showed that the south side and southwest corners, the direction of  approach for the Topeka tornado, were the least safe areas, and the north side  of homes were the safest .... both on the first floor and in the basement. He  repeated the study after the Lubbock, Texas tornado of May 11, 1970, and the  results were even more striking. The southwest portion of the houses were unsafe  in 75% of the damaged homes .... double the percentage of unsafe areas in the  northeast part of homes. As a general rule, people in basements will escape  injury despite the extreme devastation above them. Being under a stairwell,  heavy table, or work bench will afford even more protection. 

Ignorance of this conventional wisdom, combined with common sense, has saved  lives in the past. At the Pacolet Mills near Gainesville, Georgia on June 1,  1903, 550 people ran to the northeast corner of the building as the tornado  approached from the southwest. That northeast corner was the only part of the  building not destroyed. At least fifty people died in other Gainesville fabric  mills on that day, and more than 40 more died in homes near the mills.