Tornado Safety: Fact, Fiction and Survival
Tornadoes are among the most feared and deadly weather forces affecting the U.S. Tornadoes most frequently occur in the United States, but have a climatography that extends over six continents (including Africa). Once unpredictable and misunderstood, tornadoes killed far more people in ages past than they do today. Quantum advances in the science of mesoscale meteorology coupled with concurrent upgrades to remote sensing and computer modelling have allowed much improved detection and warning capabilities. Advances in science also have enabled greater resilience for communities, including improved structural engineering, warning systems and shelter programs.
Myth and legend is hard to eradicate, however. For example, in decades past it was believed that the low atmospheric pressure associated with a tornado caused buildings to, “explode.” Accordingly, the recommendation was to open windows on the side of the building away from the tornado to equalize pressure. We now understand that the tornado’s destructive force is wind loading, in which upwind sides of buildings fail and the rest of the structure fails due to gravity and/or infiltration of high velocity winds. In fact, opening windows only exacerbates the threat by creating an opening for tornadic winds to penetrate. We also heard for decades that seeking shelter from a tornado under an overpass or bridge was suitable when a tornado was threatening. We now know that is a horrible idea, since venturi effects funnel the tornado debris and extreme wind into such confined areas, often piling debris at crushing intensity.
These are just two examples of what not to do. That National Weather Service works tirelessly to build and sustain a warning program that saves lives and lessens property damage. With their partners in emergency management, state and local government, first responders and the electronic media, a framework of enhanced warning capability has been established. The average lead time for tornado warnings is now 20 minutes, so you have 20 minutes from warning issuance to the arrival of the threat. Those lifesaving minutes allow people to make correct choices. Here are tornado safety rules if a tornado warning is issued or a tornado is sighted in your area:
If you can get to a sturdy building, go Go to a safe room, basement or storm cellar If no basement is available, go to a small interior room on the lowest floor Stay away from windows, doors and exterior walls If caught in the open, find a low, flat location. DO NOT get under an overpass or bridge Watch out for flying debris, and use your arms to protect your head and neck.
For more information go to http://www.ready.gov/tornadoes