How does a tornado start?

How does a tornado start?

• what makes the wind go in circles like that? and why do hurricanes spin as well? how do they start and what keeps them spinning?

• Answer:

  Tornadoes start deep within vast thunderclouds, where a column of strongly rising warm air is set spinning by high winds streaming through the clouds's top. As air is sucked into this swirling column, or mesocyclone, it spins very fast, stretching thousands of feet up and down through the cloud, with a corkscrewing funnel descending from the cloud's base - the tornado. Once a tornado vortex forms, sustaining it requires a continuing feed of converging air from outside the storm that can be accelerated by conservation of angular momentum and that can be lifted into and exhausted by the parant thunderstorm. If this inflow is interrupted, for example by a drier airmass being entrained into the storm, or by a cool, stable downdraft/outflow airmass that may originate from another storm nearby or even from another part of the parent storm, the required moisture, heat and instability may be lost, or the air flowing into the tornado region may simply be disrupted or diverted in such a way as to cause the tornado to dissipate.