What causes the cyclonic spin in a tornado

I'm trying to figure out what makes the wind of a tornado create a spinning funnel.

Currently, there are two seperate ways a tornado is formed. Supercell thunderstorms will often have storm scale rotation which is called mesocyclone. It is known that there is air underneath the storm that is rotating horizontally. When the updraft of the storm strengthens, with the help of inflow winds, the horizontal rotating air can be tilted into the vertical. If the rotation is strong enough, a lowering from the base of the storm cloud can form and make a wall cloud. Sometimes, the wall cloud can be rotating as well.If the updraft, downdraft, and rear flank downdraft are present, this can strengthen the rotation and can create a funnel cloud. If the rotation remains strong and eventually reaches the ground, then a tornado has formed.

A non-supercell tornado does not form from organized storm scale rotation. They form from a vertically rotating air that is already occurring near the ground. This is caused by wind shear from a warm, cold, or sea breeze front, or a dryline. When an updraft moves over the rotating air and stretches it, a tornado can form.

What causes the spin in the air is know as wind shear. Wind shear is the change in wind speed and wind direction with the change in height. The following links will explain this with graphics and animation to make it easier for you to understand than for me to write a book for this answer.

http://www.srh.noaa.gov/jetstream/tstorm…

http://esminfo.prenhall.com/science/geoa…

http://www.youtube.com/watch?v=GM-abtIT6…

http://access.ncsa.illinois.edu/Stories/…

The spin is a massively enhanced version of the spinning cloud (mesocyclone) from which it forms. As the diameter of the storm cyclone decreases, its velocity increases. Google: Bernouilli's Principle for how this works.

http://www.answer5.com/education_referen…

Sound familiar?

What he said