This is in reply to cottonmouthkings' question about 
whether the safety technique of crouching down 
in the lowest floor of a building would have been 
sufficient during the Moore, OK F5 tornado:

cottonmouthkings-

Howdy!  Good question.  Most tornadoes have wind 
speeds of 150mph or less.  Unfortunately, the Moore, OK
tornado was a very powerful, very rare F5 tornado, with 
wind speeds approaching 300mph.  Those of you living in 
Moore, OK likely witnessed firsthand how homes were 
taken away down to the concrete foundation... nothing 
much could survive, above ground level, when the winds 
are that strong.  

Do not take my words as 100% accurate.  I know a lot about
tornadoes, but I am not an expert. Try thinking of your own 
solutions and then go search for "tornado safety".  

In any high-wind situation, the best thing you can do, if there 
is no time to get underground, is to stay as close to the 
ground as possible.  When the wind picks things up, they 
become airborne weapons.  This is what you want to avoid.  
Trust me.  :-)  However the closer you are to the ground, the 
lower the wind speed, thanks to surface friction.

It's like when you're running and you use your feet to skid to 
a stop.  The ground pushes back on your foot, slowing it 
down before the rest of your body above it.  This is why 
baseball players stick their feet out in front of them when they 
slide- otherwise they'd fall over!  :-)

The same thing happens with the winds in a bad storm or tornado.
The wind right at the surface starts at zero, then gets faster as you 
go up.  So I'm just making up an example, but the wind speed 
might have been 300mph at 100 feet above the ground, but only 
150mph or so at 3 feet above the ground, then 100mph or so 
1 foot above the ground, then 10mph at 1 inch and nothing right 
at the surface.  

This is why they tell you to duck during tornado drills.  Only the 
strongest tornadoes can produce strong winds very close to the 
ground.  You can see evidence of this whole surface friction idea 
if you look at the F5 tornado damage and see how the trees 
were sliced off a few feet above the ground, the level where all 
the debris was kept in the air by the wind.  The lower the level 
of destruction, the stronger the winds.  

In most tornadoes, the inner walls and rooms of a sturdy building 
will remain standing.  So it is still a good idea to find shelter on the 
lowest floor behind a few thick walls.  But it is usually better to get 
underground if you can.  If there are no buildings around, try to put 
solid earth between you and the wind.  For example, a ditch or a 
little hill.  Do *not* hide in a highway overpass, the wind is 
*worse* inside them... use a ditch instead. (why do you think the 
wind is worse inside an overpass?)

Driving away from the tornado may have helped a lot of people, 
but that is dangerous, too.  What if the tornado changes direction 
and you run into traffic or there are no more roads?  You do not 
want to be in a car when a tornado comes along.  Walls are built to 
stand still against the wind.  Cars are built to move.

I am not an expert, so don't take what I say as "The Law", but 
personally if I knew ahead of time that such a powerful tornado 
was coming, I would have driven away, trying to think of buildings 
with basements or underground shelters nearby in case I ran out 
of time or it began to hail.

That was a very good question!  Hope this helps, and I hope to 
hear more questions from all of you, soon.

CD
2/26/2001