How Supercell Storms Produce Devastating Tornadoes

Supercell thunderstorms have been responsible for major tornadoes that have demolished parts of the United States since modern day record keeping started in 1950.

Supercells are different from normal thunderstorms because they are much more organized and often have a strong circulation, which not only feeds the storm a mixture of moisture, dry air, warm air and cold air, but also aids in funnel cloud formation. The cloud base of the supercell typically has three sections. One area where there is no precipitation, the precipitation area and the lower-hanging wall cloud. Funnel clouds form where this rotating wall cloud lowers from the overall base of the storm. A tornado is born where the funnel touches the ground. An anvil cloud is often visible in supercell thunderstorms. This cloud is very high in the atmosphere and is made up of ice crystals. In the strongest supercell thunderstorms, part of the cumulonimbus cloud pokes above the anvil.

Debris from a row of homes destroyed by a tornado in Washington, Ill., is seen early Monday, Nov. 18, 2013. The tornado destroyed several hundred homes in the small town the day before. (AP Photo/David Mercer)

AccuWeather.com Expert Senior Meteorologist Henry Margusity said that tornadoes that are produced by supercell thunderstorms develop in cycles.

"The tornadoes develop, mature and dissipate," he said.

The cycling process includes tornadoes touching down, traveling distances and picking back up, Margusity said. When the tornado touches down and travels for a while, this can be thought of as the tornado maturing. When the tornado retracts into the sky, the storm dissipates.

When the tornadoes lift and go back down to the ground it produces multiple tornadoes. It is not just one isolated tornado.

"It is like a family of tornadoes," Margusity said.

The tornado that touched down in Moore, Okla., was rated an EF5 with a base larger than 1 mile and a destruction path of 17 miles. This tornado was caused by a supercell thunderstorm. The average warning time, from the time the warning is issued to when the tornado strikes, is 13 minutes. Community members were given 16 minutes from the time the warning was issued until the time the tornado ripped through Moore.

Photo courtesy of AccuWeather.com.

A similar tornado touched down in Woodward, Okla., April 14, 2012. An EF3 tornado that was on the ground for 37 minutes caused massive destruction and loss of life. The NWS issued a tornado warning at midnight and by 12:33 a.m., there were reports that a tornado had touched down.

The people of Joplin, Mo., were victims of a destructive tornado caused by a supercell thunderstorm on May 22, 2011. An EF5 tornado that was three-fourths of a mile ripped through the city, resulting in 158 deaths and more than 1,000 people injured. The Joplin tornado was ranked seventh in U.S. history of most deadly tornadoes and the single deadliest tornado since modern record keeping began in 1950, according to the NWS.

Another tornado spawned by a supercell, killed 116 in Flint, Mich., on June 8, 1953. This tornado was originally the single deadliest tornado. This EF5 tornado had a destruction path of 27 miles and moved at 35 mph.

After a warning has been issued, it is important to seek shelter immediately. With an EF3, 4 or 5 tornado, the only safe place to be is underground, according to AccuWeather.com Expert Senior Meteorologist Dan Kottlowski.

A safe room described by the Federal Emergency Management Agency (FEMA) is, "a hardened structure specifically designed to meet the FEMA criteria and provide 'near-absolute protection' in extreme weather events, including tornadoes and hurricanes," according to www.fema.gov.

However, Kottlowski said that the safe room must be reinforced with rebar and concrete. The shape of the room and the area in which it is built may also be an important role in staying safe in a tornado. Shaping the room like a dome or igloo and being mindful of which way the wind blows toward your house are two suggestions that Kottlowski makes.

For more information on how to build a safe room that is up to regulation check out FEMA's website at, www.fema.gov/safe-rooms.

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