Thunderstorms To Tornadoes: Decoding Nature's Most Violent Transformation

The Science Behind Tornado Formation

The most active time of the year for tornadoes is near and there are likely hundreds of tornadoes ahead of us before this period is over.

But how is it that tornadoes actually form?

The short of the long of it is that we’re still figuring that out.

We have a basic blueprint that we know leads to tornadogenesis – the birth of a tornado – but the finer details that can make or break a swarm of tornadoes are still a topic of deep research among meteorologists, storm chasers, and modelers.

Let’s talk about what we know about this process:

First, we need the table set for tornadoes to take shape. Here’s a quick primer for the common tornado ingredients using a common weather acronym – SLIM:

• (S)hear: Wind shear is the changing of wind speed and direction with height over a community
• (L)ift: The forcing of air upward in the atmosphere, often by a cold front or other boundary
• (I)nstability: The tendency for air to rise by itself through heating. Warmer air is more unstable and will rise faster.
• (M)oisture: Air laden with more water will be more buoyant and will tend to rise.

For a better understanding of why these ingredients matter, visit the link below:

IN DEPTH: Ingredients For A Severe Weather Outbreak

Once wind shear, lift, moisture and instability are in place, we can start whipping up thunderstorms.

All tornadoes start with a thunderstorm: When plentiful heat and humidity are in force, thunderstorms can bubble up like popcorn.

Cold fronts, dry lines or any other moving boundary can help push clouds up and up into the atmosphere until they reach tens of thousands of feet high – Often taller than planes fly.

Taller thunderstorms can interact with more ingredients such as wind shear and instability aloft. This is where the fun begins.

Thunderstorms twist as they grow: When vertical wind shear is intense near the surface, it creates a rolling tube of air that is parallel to the ground. This is analogous to the cresting of a wave as it gets into shallower water near a beach. This rolling tube of air is the origin for what could become a tornado.

Heating near the ground helps lift the horizontal tube of rolling air into the vertical, which could then become a tornado. As the thunderstorm runs into additional instability, this rotating cloud can stretch upward and downward and strengthen.

The rotating tube acts as a suction vacuum bringing up air, and that air falls as rain in areas surrounding and ahead of the strongest part of the storm. This is like the lungs of a thunderstorm that will keep breathing until the storm cannot breathe any longer.

It is at this stage that a thunderstorm becomes a supercell.

This suction vacuum also increasingly spins as heat and shear pulls the vortex skyward. When this spin becomes strong, a tornado can form.

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Tornadogenesis: As the rotation stretches, a downward extension becomes a funnel cloud. As this spinning vortex strengthens, it could reach the ground. When touchdown occurs, the funnel becomes a tornado and can kick up debris.

Tornadoes can have winds from 70 to over 200 mph, and their parent supercells can also bring winds over 60 mph and large hail.

Tornadoes are rated on the Enhanced Fujita Scale, a damage scale that ranges from EF0 (weak damage) to EF5 (incredible destruction). Winds are estimated from damage done to structures, cars and even the ground.

A tornado will continue until favorable ingredients lessen.

Jonathan Belles has been a graphics meteorologist and writer for weather.com for 8 years and also assists in the production of videos for The Weather Channel en español. His favorite weather is tropical weather, but also enjoys covering high-impact weather and news stories and winter storms. He's a two-time graduate of Florida State University and a proud graduate of St. Petersburg College.