Question

What causes tornadoes to occur in certain areas of the earth

Answer 1

Tornadoes form when warm, humid air collides with cold, dry air. The denser cold air is pushed over the warm air, usually producing thunderstorms. The warm air rises through the colder air, causing an updraft. The updraft will begin to rotate if winds vary sharply in speed or direction1

Answer 2

It is  obseved that tornadoes generate in the region's  that are cool, have dry air in the upper levels of the atmosphere caps, warm and have humid surface air.