What Is A Supercell Thunderstorm And Why Do Meteorologists Keep A Close Eye On Them?

Severe Thunderstorm Sweep Through Midwest

The supercell, king of thunderstorms, disruptor of the Great Plains, is a dangerous weather threat wherever it forms. Tornadoes, flooding, enormous hailstones, damaging winds and lightning are some of the threats that these kings possess.

Let the royal music play and grab a crown: let’s chat about what supercells are and what these monsters are capable of.

What Sets Supercells Apart

An ordinary thunderstorm in the middle of summer can produce lightning and a heavy downpour. But within an hour or less, it rains itself out and fizzles.

Supercell thunderstorms, however, can last several hours and track hundreds of miles.

The key to that longevity is wind shear.

If winds above the ground are much faster and from a different direction than near the ground, that causes the air between to spin slowly around a horizontal axis. You can visualize this by placing a pencil flat between your hands and moving your hands in opposite directions.

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In that environment of high wind shear, a growing thunderstorm's upward current of air, or updraft, tilts that horizontal tube of rotation upright. It also stretches that tube vertically, which makes it spin faster.

That becomes the supercell's "mesocyclone". This is the spin that can lead to a tornado. It is also what keeps a supercell going for minutes to hours.

Supercells can form anywhere where the ingredients needed for their formation are available. They are often seen in the South, Plains and Midwest.

Impacts

Supercells are a major tornado producer. Supercells are responsible for spawning most tornadoes – violent ones in particular. But, according to the National Severe Storms Laboratory (NSSL) as few as 20% of all supercell thunderstorms produce tornadoes.

The best-organized supercells may spawn multiple tornadoes, known as a tornado family. Some of these can stay on the ground for a long time, sometimes up to an hour or so. On rare occasions, supercells can produce dozens of tornadoes.

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Huge hail can shred homes. Quite often, especially in the Plains states, the extreme instability helping to fuel supercell thunderstorms can lead to prolific hail. Some hail in recent years has been larger than DVDs.

Supercells Can Weather Different Crowns

High-precipitation (or HP) supercells contain heavier concentrations of rain and hail wrapping into the mesocyclone. The precipitation can sometimes obscure the storm's structure, including wall clouds and tornadoes. Tornadoes obscured by heavy precipitation are typically known as "rain-wrapped." Wedge tornadoes are most frequently associated with HP supercells.

Low-precipitation (or LP) supercells are typically rather skinny, but can produce photogenic tornadoes and large, sporadic hailstones.

This type of smaller supercell is usually found in the Plains or High Plains, or farther away from a source of humidity. It's easy to spot by its distinctive, bell-shaped structure.