A tornado is a violent, rotating column of air which is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. The most intense of all atmospheric phenomena, tornadoes come in many shapes and sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust.

Most tornadoes have wind speeds between 40 mph (64 km/h) and 110 mph (177 km/h), are approximately 250 feet (75 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme can attain wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km).

Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout. Waterspouts have similar characteristics to tornadoes, characterized by a spiraling funnel-shaped wind current that form over bodies of water, connecting to large cumulus and thunderstorm clouds. Waterspouts are generally classified as non-supercellular tornadoes that develop over bodies of water. These spiraling columns of air frequently develop in tropical areas close to the equator, and are less common at high latitudes.

Other tornado-like phenomena which exist in nature include the gustnado, dust devil, fire whirls, and steam devil.

Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America. They also occasionally occur in south-central and eastern Asia, the Philippines, east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.

Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes, as well as by the efforts of storm spotters.

There are several different scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by damage caused, and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.

A tornado outbreak sequence (or extended tornado outbreak) is a period of continuous or near continuous high tornado activity consisting of a series of tornado outbreaks over multiple days where there are very little or no days with a lack of tornado outbreaks. Major tornado outbreak sequences occurred in the United States in May 1917, 1930, 1949, and 2003. Another exceptional outbreak sequence apparently occurred during mid to late May 1896. Tornado outbreak sequences tend to dominate the tornado statistics for a year and often cause a spike in tornado numbers for the entire year. Read more ...

  Tornadoes   Google Videos

Tornado Alley

Tornado Alley is a colloquial term for the area of the United States where tornadoes are most frequent. Although an official location is not defined, the areas in between the Rocky Mountains and Appalachian Mountains are the areas usually associated with it. Tornadoes are most common here because it is the region where warm, moist air from the Gulf of Mexico meets cold, dry air from the Rocky Mountains and Canada, creating intense, tornado-producing thunderstorms known as supercells.

In the News ...

The November 17, 2013 tornado outbreak was the deadliest tornado outbreak during the month of November on record in the U.S. state of Illinois. The event resulted in many tornadoes across Illinois, Missouri, Michigan, Indiana, Kentucky, Ohio, and Tennessee with at least eight fatalities. Damaging straight-line winds were seen over a larger area including Iowa, Wisconsin, Tennessee, Pennsylvania, and New York. More than 390,000 energy customers lost power in Michigan, more than 160,000 in Indiana, more than 160,000 in Illinois and approximately 37,000 in Missouri. Non-tornadic deaths and injured include one killed in Jackson County, Michigan when a tree fell on a car, one killed by live wires in Shiawassee County, Michigan, one critically injured after touching a downed wire in Detroit, and two minor injuries in a home damaged by wind in Ohio.

A Waterspout in Florida   Astronomy Picture of the Day - July 17, 2013

Pictured above is one of the better images yet recorded of a waterspout, a type of tornado that occurs over water. Waterspouts are spinning columns of rising moist air that typically form over warm water. Waterspouts can be as dangerous as tornadoes and can feature wind speeds over 200 kilometers per hour. Some waterspouts form away from thunderstorms and even during relatively fair weather. Waterspouts may be relatively transparent and initially visible only by an unusual pattern they create on the water. The above image was taken earlier this month near Tampa Bay, Florida. The Atlantic Ocean off the coast of Florida is arguably the most active area in the world for waterspouts, with hundreds forming each year. Some people speculate that waterspouts are responsible for some of the losses recorded in the Bermuda Triangle.

  A tornado's heading your way: Now what?   CNN - May 25, 2013

You've just that heard a tornado is headed directly toward you. You don't have a safe room, and you're not near a shelter. Do you hunker down and hope for the best or do you flee? Emergency officials have long held that you should just stay put if you're inside anything other than a mobile home -- and head for the lowest floor and the inner-most room. Yet even with improvements to severe weather prediction, no one can say with certainty what a tornado will do.

2013 Moore Oklahoma Tornado   Wikipedia

May 20, 2013 Moore Oklahoma Tornado   Crystalinks

  Mother's instinct saves lives of 3 sons as tornado approached home   CNN - May 23, 2013
As the monster tornado approached, Terimy Miller put her three sons in a closet in their Moore, Oklahoma, house. But something didn't feel right. "It was just that feeling," Miller told CNN's Brooke Baldwin on Wednesday. "I just got to get out of here. I'm not chancing this." So she put her three boys -- ages 11, 7 and 6 -- in the family car. She was moving so fast that she couldn't round up the two family dogs, which were somewhere outside. As they prepared their escape, she and son Jules heard a local weatherman on television advise families in Moore that if they didn't have a storm shelter, they should abandon the house. "We got away from the storm," said son Jules, 7. Confirmation of the mother's intuition came when she and her boys returned to the house. Miller hyperventilated. She cried. The tornado had annihilated the home.

Oklahoma Tornado Photos: 2-Mile-Wide Twister Destroys Town   National Geographic - May 21, 2013
A woman carries her child past the rubble and remains of the Plaza Towers Elementary School in Moore, Oklahoma, on May 20.

Why Was the Moore, Okla., Tornado So Severe?   Live Science - May 21, 2013
A monstrous tornado that ripped through Oklahoma Monday May 20 piling cars on top of one another, demolishing an elementary school and killing several adults and children, may owe its power and deadliness partly to a convergence of jets of air, say meteorologists.

4 Things You Need to Know About Tornado Season   Live Science - April 11, 2013
1. Tornadoes can happen anywhere, any time of year.
2. The difference between tornado watches and warnings.
3. Don't open your windows. Or shelter under an overpass.
4. Tornado season can't be forecasted.

US tornado outbreak was 'biggest ever'   BBC - May 2, 2011
The outbreak of tornadoes that ravaged the southern US last week was the largest in US recorded history, the National Weather Service has said. The three-day period from 25-28 April saw 362 tornadoes strike, including some 312 in a single 24-hour period. The previous record was 148 in two days in April 1974. The tornadoes and the storm system that spawned them killed at least 350 people in Alabama and six other states. It was the deadliest outbreak since 1936.

April 25-28, 2011 US Tornado Outbreak Wikipedia


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