09 June 2013


As climate change accelerates, extreme weather events in all seasons are becoming more severe.  This includes tornadoes, whose rotational windspeed can exceed 300 mph and whose diameter can exceed 2 miles.  Just such a nightmare twister struck El Reno, OK, on May 31, 2013.  The El Reno twister was clocked by Doppler radar at 295 mph, and its width reached 2.6 miles.  (Click on the image above of a much smaller tornado ~ notice how it still dwarfs the white building at center left.)

Most folks who live in Tornado Alley take tornado season very seriously.  They pay attention to weather alerts, and understand the need for a storm-proof safe space within a home or public building ~ either a dedicated tornado shelter or an interior room or hallway which is surrounded by weight-bearing beams and has no windows.

For meteorologists, the advent of weather satellites, together with Doppler radar, has improved advanced warning time considerably.  Even so, when a tornado is powerful enough to be rated F5 on the Fujita scale, the scale of destruction can resemble the aftermath of an atomic bomb blast.

The situation is compounded when teams of amateur and professional storm chasers, as well as foolish thrill-seeking civilians, use their vehicles to actually place themselves near, or in the path of, an oncoming tornado.  Such activity can become a traffic jam, especially when combined with the flow of vehicles trying to escape the storm.  With nowhere to go and nowhere to hide, such crowds ironically become a potential target for approaching disaster.

Thus John Rennie's observation during the El Reno tornado's aftermath that "It became clear that surviving an encounter with a tornado is not just a matter of doing the right things.  It's also about not making some lethal errors."  Here are a few of them ~

  • Don't be in a car during a tornado .... Tornadoes can change course unpredictably, and it isn't always easy to see their funnels in the murk of bad weather surrounding them .... Moreover, according to NOAA, tornado warnings give on average only 13 minutes notice.  That's enough time to drive miles away ~ but not with throngs of cars all trying to abandon the area at once.  So trying to drive away during that small window of opportunity could easily lead to your being trapped in your car as the tornado bears down on you.  No car's safety features offer much guarantee in that case.  The greatest harm may come from flying debris, which can be of any size or composition, moving on average about 100 mph .... Moreover, even if your car isn't tossed by a tornado or shredded by debris, and even if it isn't stuck in traffic, the danger isn't over.  Severe rain and hail can make driving hazardous .... Torrential rain also leads to local flooding, so it's not uncommon for cars driving away from tornadoes to end up underwater.  According to the National Weather Service, most of the people killed by floods during tornadoes drown inside their cars.
  • Don't hide under an overpass .... Overpasses seem as though they would offer great protection from the wind ~ and sometimes they can, if the tornadic winds are coming primarily from certain directions.  From other directions, however, the narrow confines of an overpass will focus and intensify the winds, and funnel flying debris toward anyone hiding inside.  Winds during tornadoes are highly changeable, so even if conditions under an overpass seem benign at first, they can rapidly (and lethally) change for the worse .... If you're in a car and need protection from a tornado, what should you do?  The best option would be to leave the car and try to get inside any nearby house, store, office building or other sturdy structure ~ ideally, one with a good basement or a proper tornado shelter.  But short of that, counter intuitively, if you can't find indoor refuge, your best bet may be to lie flat in a ditch, holding onto something heavy as an anchor, with cushions or blankets over you as a shield against debris.
  • Don't open the windows and doors of your house.  If you do have the option of sheltering indoors, you want to seek a spot that is underground, or in a windowless space toward the center of the structure .... Be attentive to what might fall on top of you in the event of a building collapse ~ if you can get under a strong piece of furniture for additional protection, do it.  But don't try to protect the house as a whole by opening all the windows and doors in the interest of making it easier for the pressures inside and outside to equalize.  [That received wisdom] is a myth.  When a tornado hits a house, it subjects the structure to complex, fast-changing forces that push and pull in rapid succession .... exposing any weakness.  Opening the windows and doors only succeeds in letting the winds into the house so that internal supports can be shaken apart, which weakens the structure even more.
Here is a video demonstration of how leaving a house door open makes a catastrophic difference in its stability.

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