Tornadoes are formed from a thunderstorm.
Then there will be a change in the wind direction and wind speed along with Air mixing. This causes it to swirl horizontally.
The swirling picks up more warm air from the ground as it collects more air it turns into a funnel where it stretches and becomes longer.
After this process it will stretch towards the ground and when it touches the ground it becomes a tornado.
The dry, cool air mostly come from south of Canada while the warm, moist air comes from the north of Mexico. To form a tornado it can take rearly seconds for one to form but could also take longer.
Hope this helps! :3
