What is a Tornado?

Have you ever heard of tornadoes? A tornado is one of the most impressive and dangerous weather events, it’s the most powerful thing that can occur during a thunderstorm.

What’s a tornado?

A tornado is a a violently rotating column of air, pendant from a cumulonimbus cloud, the typical cloud of thunderstorms. Tornadoes are often visible as a funnel cloud, but not always. The column of air is rotating counterclockwise in the northern hemisphere and clockwise south of the equator.

During thunderstorms the clouds can grow upwards, higher and higher, into the atmosphere until they reach the tropopause at 18,000 metres (59,000 ft). During this events gusts, heavy rain, lightnings and tornadoes can occur. In the center of the tornado the air pressure is very different from the air pressure outside the tornado: this is why strong winds go from the ouside-in the tornado at high speed. Winds can blow over 65 mph up to 200 mph!

Diagram of a thunderstorm with a tornado – Credits: NOAA

 

How can we measure the intensity of tornadoes?

Measuring the wind’s speed is very difficult and extremely dangerous. This is why Professor Fujita came up, in 1971, with the Fujita Scale, a particular scale that goes from F0 to F5 that estimate the wind strenght based on the damage made by a tornado. In 2007 this scale was perfected and now it’s called the Enhanced Fujita Scale. Its uses three-second gusts estimated at the point of damage. A tornado EF0 has gusts that blow up to 65-85 mph; an EF1 up to 110 mph; EF2 up to 135 mph; EF3 up to 165 mph; EF4 up to 200 mph; EF5 over 200 mph.