The when looking at a tornado one can only wonder how such a ferocious force of nature could be constructed? The answer requires a little bit of physics and a sense of excitement for the majesty of nature.
Tornadoes are formed when warm wet air collides woth cool dry air causing clouds to spin faster and faster.   A tunnel is formed from the spinning air and the moment it strikes the ground the phenomina upgrades from a wind funnel to a tornado.  Ultimately, a tornado is a vortex of swirling air that extends from clouds.

Most tornadoes, 69% of the 800 in the U.S., are classified as weak tornadoes.  They last less than fifteen minutes and have wind speeds that don't exceed 110 mph.  On the Fujita scale, the scale for measuring the intensity of a tornado, these rate either a 0 or a 1 and cause minimal damage. 

Approximately 29% of tornadoes in the U.s. are considered strong and cause approximately a third of all tornado deaths.  They last approximately 20 minutes and their windspeeds can reach above 200 mph.  The ferocity of these wonders earns them a 2 or 3 rating on the Fujita scale and can tear roofs off houses and destroy mobile homes.

Violent tornadoes make up only 2% of all tornadoes in the world.    They are the cause of 70% of all tornado deaths  and last on average over an hour in duration ad have wind speeds that reach up to 365 mph.  They secure the highest score on the Fujita scale from a 4 to 5 and hold the records for the fastest recorded wind speeds in the world.