Why does one thunderstorm fizzle in minutes while another rotates for hours?

Whether a thunderstorm fizzles or rotates for hours depends mostly on how the wind changes with height. Every thunderstorm runs on rising warm, moist air, but with little wind shear the storm cuts off its own fuel and rains itself out. If the wind changes enough in speed or direction with height, the downdraft is separated from the updraft, and the storm may become a supercell whose mature stage can sustain itself for several hours.

Start with the basics. Thunderstorms generally require moisture, an unstable air mass and a lifting force. As the moist air rises it cools and condenses, and the condensing releases latent heat, which lets the rising air cool less than the air around it and keep climbing. All thunderstorms go through three stages: developing, mature and dissipating.

In the mature stage the rising air hits a cap, often the tropopause, and spreads out into the anvil shape you see in storm photographs. If the updraft is strong enough, droplets are held aloft long enough to grow so large that they do not melt completely and fall as hail. An updraft and a downdraft now exist at the same time.

That is also the storm's weakness. In the dissipating stage the downdraft hits the ground and spreads out as a downburst, and the cool air cuts off the inflow. A single-cell storm in low wind shear lasts only 20 to 30 minutes.

A supercell avoids this by keeping the two drafts apart. It is a thunderstorm with a mesocyclone, a deep, persistently rotating updraft. Supercells tend to last 2 to 4 hours, and some tornadic ones have lasted more than 7 hours. The first storm identified as a supercell was the Wokingham storm over England in 1959, studied by Keith Browning and Frank Ludlam in 1962.