# How Tornadoes Form A miniature supercell made of particles: see how warm air, wind shear and a rotating updraft make a tornado, and mix your own storm\. By sunny\-moon\-497ed430 Topic: Earth & Geography [Open the interactive Jig](https://ask.jig.com/j/p3cw1dhTKFLh) ## Transcript ### 1. How Tornadoes Form A tornado is a spinning column of air that reaches from a thunderstorm all the way down to the ground\. This miniature storm is made of thousands of moving specks of air, rain and dust\. Let's find out where the spin comes from\. Drag to turn the storm\. Pinch or scroll to look closer\. ### 2. Warm air below, cool air above On a spring afternoon, warm, moist air sits near the ground, shown in amber\. Cooler, drier air lies above it, shown in blue\. Warm air is lighter, so it starts to rise, like bubbles in a pot of soup\. The warmer and wetter the low air, the harder the storm can lift it\. ### 3. Winds that change with height Near the ground the wind is gentle\. Higher up, a strong wind blows the other way\. This change of wind with height is called wind shear, and it sets the air rolling sideways, like a pencil rolled between your hands\. Storm forecasters look for about 50 mph of difference between surface winds and winds around 18,000 feet up\. ### 4. The updraft tips the roll A storm's updraft is a powerful current of rising air\. When it meets the rolling tube, it lifts the middle and bends the roll upright\. Now the spin points up and down instead of sideways\. The lifted tube makes two spinning legs\. One turns clockwise, the other counter\-clockwise\. ### 5. A spinning storm The counter\-clockwise leg grows stronger and the whole updraft starts to turn\. A storm with a rotating updraft is called a supercell, and its spinning heart is the mesocyclone\. Under it, a low wall cloud often hangs from the cloud base\. A mesocyclone can be up to 10 miles wide\. It often spins for 20 minutes to an hour before a tornado forms\. ### 6. Downdrafts wrap around Rain falls out of the storm and drags cooler air down with it\. Behind the spinning updraft, a sinking current called the rear\-flank downdraft wraps around it\. Scientists think this helps squeeze the spin into a tighter knot\. Scientists are still studying exactly why some spinning storms make tornadoes and most do not\. ### 7. Stretch and spin faster The updraft stretches the spinning air upward, so the column gets thinner\. Like a figure skater pulling in their arms, a thinner column spins faster\. When the low pressure in the core cools the air enough, a cloud funnel appears and reaches down\. It counts as a tornado once the spin touches the ground, even before the funnel does\. The swirling dust shows where it is\. ### 8. Roping out Most tornadoes last less than ten minutes\. When cool, sinking air cuts off the warm air feeding the storm, the funnel tilts, thins into a twisting rope and fades away\. The storm itself may go on and make another\. Tornado winds range from about 65 mph on the weakest rating, EF0, to more than 200 mph on the strongest, EF5\. ### 9. Your storm lab Now mix your own storm\. Try the four controls and see when the spin can reach the ground\. A tornado needs warm, moist air, strong wind shear and just the right downdraft\. Too strong a downdraft cuts off the warm air and the funnel ropes out\. The wind readout is an estimate for this model\.