Weather Whys: How do tornadoes form?


Tornadoes are a severe weather event that happen every year in southern Colorado, especially over the Eastern Plains. How do they form?

First, we need wind shear.

Winds high at the atmosphere travel faster than the winds at the surface. There’s also a temperature difference. The air higher up is cooler, and the air down below is usually warmer. Temperature aside, this difference is wind speed and even direction create wind shear–the interaction between the two layers moving at different rates. 

This causes the area between the layers to begin rotating, and forms a horizontal column of rotating air. 

This rotating air is horizontal, not vertical like a tornado. So how do we flip it?

It takes a thunderstorm! A thunderstorm has a strong updraft that feeds into the storm and fuels its growth as well as a downdraft that expels cool air from the storm. Sometimes the storms themselves are rotating, These are called super-cells. 

This strong updraft pulls the rotating column of air up and turns it vertically. This creates a tornado. The storm itself undergoes a few more steps in between as the funnel reaches toward the ground, but this is the basic mechanism that creates a tornado. 

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