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The Spring 2011 issue of The Earth Scientist is focused on modernizing seismology education. Thanks to IRIS, you can download this issue for free as a pdf. Print copies are available in our online store.
This photograph of a cumulonimbus cloud was taken near Fort Lupton, Colorado. You can see some towers growing in this cloud.
Click on image for full size
Photo courtesy of Gregory Thompson

Supercell Thunderstorms and Squall Lines

A supercell thunderstorm is a huge rotating thunderstorm. It can last for several hours as a single storm. These storms are the most likely to produce long-lasting tornadoes and baseball-sized hail. Tornadoes produced from supercell thunderstorms are typically the largest and most damaging tornadoes due to the long duration of the storms. Several tornadoes can be produced from one supercell thunderstorm.

There are two types of supercell thunderstorms. One type brings high amounts of precipitation, creating downbursts, flash floods, and large hail. The other type brings low amounts of precipitation, developing tornadoes and large hail.

A squall line consists of several thunderstorms banded together in a line. Usually a squall line forms between a cold front and a warm front. A squall line can form from an individual storm that has split. This split storm helps to form the line of storms.

There are two types of squall lines. One type is a line of cumulonimbus clouds that grow and decay; the other is a line of steady supercells. Squall lines can be just as severe as a supercell thunderstorm. A squall line can produce heavy precipitation and strong winds. Most of the precipitation in the United States is from a squall line. Squall lines can extend over 600 miles (1000 km) when associated with thunderstorms.

Last modified May 27, 2010 by Becca Hatheway.

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