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how does a tornado form step by step
A tornado is a rope of air spinning at up to over two hundred miles an hour, often born under a giant rotating thunderstorm. Let's build one.
That funnel is only cloud, water droplets. The real tornado is the spinning air itself, and the swirl of debris at the ground shows where it touches.
Step one: warm, moist air near the ground under cold, dry air higher up. Warm air wants to rise, and when it breaks through it becomes the storm's updraft.
Step two: wind shear. Wind blows faster, and turns, as you climb. That drags the layers past each other and rolls a sideways tube of spinning air.
Step three: the storm's updraft catches the tube and tips it upright. Now a whole rotating column of rising air sits inside the cloud: the mesocyclone.
Step four: the spinning column stretches down and narrows, and narrowing makes it spin much faster, like a skater pulling in her arms. It touches down.
Warm moist air, shear, tipped upright, stretched tight: four steps, one tornado. Most rotating storms never get past step three.
A tornado is spin that a storm tips upright and then squeezes tight, so it only needs the right winds to wake it.