How it works
The parts of a thunderstorm are drawn here on its whole life cycle, left to right: the cumulus stage, the mature stage and the dissipating stage.
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Growing, then mature
In the cumulus stage an updraft of warm, moist air pushes a cumulus cloud upward until it looks like a tower. In the mature stage rain begins to fall and drags air down with it, so an updraft and a downdraft stand side by side, and the top flattens into an anvil.
Gust front, then fading
Where the rain-cooled air spreads along the ground it forms a gust front, sometimes under a shelf cloud. In the dissipating stage the downdraft cuts off the updraft, and with no warm, moist air coming in the storm dies away.
Questions and answers
What are the three stages of a thunderstorm?
The cumulus stage, also called the developing or towering cumulus stage, then the mature stage, then the dissipating stage.
What is the difference between an updraft and a downdraft?
An updraft is a current of rising air that feeds the storm. A downdraft is a column of air sinking toward the ground, usually with the rain.
What is a gust front?
The leading edge of the gusty winds that spread out from a thunderstorm's downdraft. A shelf cloud, a low wedge of cloud attached to the storm's base, sometimes forms along it.
Why does a thunderstorm have a flat top?
The updraft rises until the air around it is about as warm as it is, or warmer. The cloud stops growing upward there and spreads out flat, in the shape of an anvil.