Robert Green wrote:
"dpb" wrote in message
...
....

All things considered, a tornado is basically a natural vacuum cleaner.
Light items probably go straight up like rockets and cars and combines
probably bounce around inside the funnel stratified by weight until their
equilibrium is disturbed (a collision with more debris enter the base) and
the item falls out.
....

Not really. There is reduced pressure, true, but afaik there still are
not really definitive measurements of the actual minimum pressures to be
expected in the core vortex. There are eyewitness accounts from folks
said they watched their aneroid barometers during an event that claim as
much as 5" Hg drop, but all the vortex models and what data have been
collected are significantly less than that (more on the order of 100
mbar for F5-scale vortices).

The bulk of the damage and the tendency to move things is the bulk wind
velocity air pressure force. The legend that the pressure drop
"explodes" houses is just that; in reality, roofs tend to come off and
the damage looks like it's from the inside out because of the lift force
from the Bernoulli principle--lower pressure generated by higher
velocity owing to shape differential. It's the same thing as airplane
wing lift force.

Yes, there are lots of photos in daylight; I've seen a number myself.
Thing is, there aren't many that actually show the movie scenario of
that kind of stuff rotating around in the middle simply because even in
daylight by the time you have that much stuff in the air there's so much
dirt and small debris the visibility is occluded. Eventually, one of
the watch/chaser instrumented packages or vehicles will indeed get some
footage but I'm not holding my breath on seeing the bus and the cow
circling one another as in the movie.

Yes, there are seemingly incredible events; a sheriff's officer in his
car was killed while trying to serve as early warning by a second EF-5
spawned N of Greensburg the same evening. It ended up some mile or so
off the road from where they think he was parked. An automobile is
light enough that indeed it can become airborne but again, it's almost
all wind forces, not "sucked up" by the pressure differential. Heavier
items also get carried along and thrown around because they have larger
surface area.

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