A tornado is a tube of violently spinning air that touches the ground. Wind inside the tornado spins fast, but the actual 'circle' of wind around them is huge. This makes tornadoes very dangerous. Tornadoes are especially dangerous to people in cars or mobile homes and about 60 people are killed by tornadoes every year. The word "tornado" might come from the Spanish word tronada (thunderstorm), which comes from the word tronar (to thunder).
Tornadoes destroy things. They can tear houses to pieces and often leave people homeless. Tornadoes can be caused by winds that have been going opposite directions with humidity. They are smaller than hurricanes but stronger. Nearly three quarters of the world's tornadoes happen in the United States. However, they can happen anywhere.
Tornadoes mostly happen during strong thunderstorms called super cell storms. They cause a lot of damage to anything in their path. Tornadoes are ranked on the Enhanced Fujita scale, from EF0 to EF5. EF0 is used for tornadoes that cause the least amount of damage, and EF5 is used for tornadoes that cause the most amount of damage.
Tornadoes can happen in nearly any part of the world. In the United States, a tornado has happened in every state. The middle part of the United States is nicknamed "Tornado Alley" because of the number of tornadoes there. A tornado can have wind speeds of over 300 miles per hour (480 km/h). Most tornadoes have wind speeds less than 110 miles per hour (180 km/h), are about 250 feet (80 m) across and travel a few miles before disappearing. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, and steam devil; downbursts are frequently confused with tornadoes, though their action is not similar.
Characteristics
Condensation funnel
A tornado does not necessarily need to be visible; however, the extremely low pressure caused by the high wind speeds and rapid rotation usually causes water vapor in the air to condense into a visible condensation funnel. The tornado is the vortex of wind, not the condensation cloud.
Tornado family
A single storm may produce multiple tornadoes and mesocyclones. Tornadoes produced from the same storm are referred to as a tornado family. Sometimes multiple tornadoes from distinct mesocyclones occur at the same time.
Occasionally, several tornadoes are spawned from the same very large storm. If there is no break in their activity, this is considered a tornado outbreak, although there are various definitions. A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence, occasionally called an extended tornado outbreak.
Sometimes, tornadoes happen in groups. 148 tornadoes struck on the same day in April 1974. Many towns in the midwestern United States and Canada were destroyed. More than 300 people died. They were hit by flying wrecks, buried under houses, and thrown by powerful winds. That day, students in Xenia, Ohio were practicing for a play on the auditorium stage. One girl looked out the window and saw the tornado. The students ran into the hall, covering their heads. A few seconds later, all the school buses flew right onto the stage.
A man in another town hid under the couch in his living room. He held onto one couch leg. The tornado struck his house, and winds blew around him. When the tornado left, he was outside. There was no house. The couch had disappeared, and he was only holding onto one couch leg.
Damage scale
The Fujita scale and the Enhanced Fujita Scale rate tornadoes by how much damage they cause. The Enhanced Fujita (EF) Scale was an update to the older Fujita scale. The updated scale uses engineered wind estimates and has better damage descriptions. The EF Scale was designed so that a tornado rated on the Fujita scale would get the same numerical rating, and was used in the United States since 2007. An EF0 tornado will probably damage trees but not big buildings, whereas an EF5 tornado can rip buildings off their foundations leaving them destroyed and even damage big skyscrapers.
In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. Less than 1% of tornadoes are violent tornadoes (EF4, T8 or stronger).