Most of the tornadoes occur right down the middle of the country. In tornado alley, the cool, dry air dropping from the Rockies slams into the warm and humid air coming from the Gulf of Mexico. This is a recipe for trouble.
Three ingredients have to be in place in order for a tornado to drop out of the sky. First the atmosphere has to have a triggering mechanism like a front or dry line to get the storms going.
There has to be enough low level moisture in place to fuel the storm and keep it alive.
Instability is a must have. This is where the temperature cools as you go up in the atmosphere. Instability will promote rising motion to make for strong updrafts.
Within a powerful storm, the wind direction will change with height plus the wind speed will increase as you go higher up. This combination will create an invisible horizontal spinning effect like a steamroller in the lower atmosphere.
Rising air within the storm's updraft tilts the rotating air vertically. As the swirling motion touches ground and picks up dirt and moisture a tornado is born.
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