Re: why do tornadoes have a cone shape

The "cone" shape of a tornado is called a vortex.
Have you ever watched water drain down the bathtub?
As the water level drops a water vortex forms near the drain.
(Try IT!)

A tornado is similar except that instead of water going down
the drain, a tornado is from strong updrafts in a supercell thunderstorm
forcing air upwards.

The pressure at the base of each of these is greater near the bottom
than at the top, so the cone spreads out the farther up you go.
At the bottom of the tub, more water creates a higher pressure.
Near the surface, the air pressure is greatest and decreases 
with altitude.
This creates the "cone" or "funnel" shape of a vortex flow, 
whether in your bathtub or as in a tornado.

For more educational information try out... http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/svr/torn/cyc/mrcyc.rxml
OR for some tornado pictures... http://www.chaseday.com/chaseday5.htm