What causes a tornado? Storm Team 5 has the answer

Beyond The Forecast

GREEN BAY, Wis. (WFRV) – As of August 18, Wisconsin has seen a total of 17 tornadoes throughout the state in 2020. In Northeast Wisconsin, three have been recorded in Winnebago County this year. Naturally, it begs the question, what causes a tornado? It is a loaded question, but let’s dive into the basics.

A tornado itself is a rapidly rotating column of air stretching from a thunderstorm to the ground. The most violent tornadoes tend to form from strong thunderstorms known as supercells that are fueled by warm, moist air. It is made visible by liquid droplets of water exactly the same as cloud droplets. According to the National Severe Storms Laboratory (NSSL), roughly 20 percent of all supercells produce tornadoes.

A big factor needed is wind shear within a thunderstorm. Wind shear can be broken down into two types of categories: speed wind shear and directional wind shear.

Speed wind shear is when wind speeds vary with height which creates a rolling effect. Directional wind shear is when wind speed changes direction going up with height. Both can cause horizontal rotation that can lead to the birth of a tornado.

The horizontal rotation caused by wind shear can then get caught up in a thunderstorm updraft, or a warm upward movement of air. That updraft then can shift the horizontal spinning motion vertically. Once the rotation is shifted vertically, a tornado can be born from the storm.

These are the basics of how a tornado can form, however, there are many other small factors that contribute to the formation. This is the reason why tornadoes come in different sizes and intensities based on the type of storm.

Annually, Wisconsin average 23 tornadoes per year. Historically, the month of June is typically the peak month for tornadoes in Wisconsin.

In the event of severe weather, be sure to stick with Storm Team 5 on-air, online, and on our app:


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