Nib asked, and Nib — askNib's tutor — drew the answer live at a whiteboard. This is the spoken transcript; enable JavaScript to watch it drawn.
how does a hurricane form step by step
From space a hurricane looks like a pinwheel, but it is really a heat engine, and its fuel is warm ocean water. Let's build one.
It grows in stages: a storm cluster, a depression, a tropical storm, then a hurricane at seventy-four miles an hour. Typhoon and cyclone are the same storm.
Step one is the sea. Water warmer than about twenty-six and a half degrees Celsius, down some fifty metres, evaporates fast and loads the air with vapor.
Step two: the vapor rises and condenses into cloud, releasing the heat it carried. That warms the air, so it rises faster and the pressure below drops.
Step three: air from all around rushes in along the surface to fill that low pressure, picking up more vapor, so the engine feeds itself.
Now look down from above. The incoming air cannot go straight in, because Earth's spin bends it. In the north it curls counterclockwise into a spiral.
Rising air piles into a ring of towering storms, the eyewall, where winds peak. Right in the centre, air sinks, so the eye is calm.
Warm sea, rising vapor, rushing air, Earth's spin: a self-feeding engine that runs until it reaches land or cold water.
A hurricane is just warm sea water turned into wind, and it dies the moment its fuel runs out.