LEARNING CENTER
The purpose of this page is to teach you the basics of severe storms and tornado formation. Having a
better understanding of what you will be seeing in person will make your tour more enjoyable.
SUPER-CELLS
are the ultimate storms!
Large, long-lasting thunderstorms known as
"supercells" are responsible for producing the
strongest tornadoes, large hail, and other
dangerous winds. Some general characteristics
help identify supercells from a distance. Air
rising into the storms at speeds up to 170 mph
helps give them a hard, cauliflower look. The air
is turning as it rises, which can give parts of the
clouds a corkscrew appearance. Atop the
column of rising air a dome or cloud, called an
"overshooting" top, forms, also with a hard look.
Tornadoes, especially large ones, usually drop
from the supercell near the edge of the rain-free
area under the storm.
The millions of tiny water droplets and ice crystals that we see as a cloud hides much of the action
going on inside a supercell thunderstorm. But, the appearance of the cloud helps show what's
happening inside. The rotating, rising column of air known as a "mesocyclone" is the heart of a
supercell. The mesocyclone makes these thunderstorms different from their weaker cousins. Like any
thunderstorm, a supercell needs warm, humid air in the lower atmosphere, much colder air aloft and
something to give the air near the ground an upward shove. Often, this upward shove is as simple as
heated air rising because it's lighter than surrounding air. Rising warm air shoots upward like a hot air
balloon where the air surrounding it is cold. The greater the temperature contrast, the more energy the
rising air has. As water vapor in the rising air condenses into cloud droplets or turns into ice crystals, it
releases heat, which adds to the storm's power.
All thunderstorms are fueled by temperature contrasts and
the heat released by the air's humidity condensing into
clouds. To become a supercell, a thunderstorm needs
strong winds coming from different directions at different
altitudes high above the ground. The right combination of
wind speeds and changing directions gives the rising air
the twisting motion of the mesocyclone. All of this helps
crease a complex pattern of rising and falling air that keeps
falling rain and hail from dropping back into the
thunderstorm's rising air. Normal thunderstorms are
strangled, often in less than a half hour, as rain falls into the
rising, warm air. This cuts off the storm's fuel supply of
warm air. Supercells can last for hours, moving hundreds of
miles. The turning motion of the air rising in the
mesocyclone helps give tornadoes extra power. Scientists
are still trying to work out the exact links.