Tornado

A tornado, also known as a twister, is a rapidly rotating column of air that extends vertically from the surface of the Earth to the base of a cumulonimbus or cumulus cloud. These powerful weather events often appear as a visible funnel-shaped cloud, with rotating debris and dust near the ground. Most tornadoes have wind speeds less than 180 kilometers per hour (110 miles per hour), are about 80 meters (250 feet) across, and travel only a few kilometers before disappearing.

However, the most extreme tornadoes can reach wind speeds of more than 480 kilometers per hour (300 mph), span over 3 kilometers (2 miles) in diameter, and remain on the ground for more than 100 kilometers (62 miles). Tornadoes come in different types, including the multiple-vortex tornado, landspout, and waterspout. Waterspouts form over bodies of water and are common in tropical areas near the equator, though they are less frequent at high latitudes.

Tornadoes most commonly occur in North America, especially in central and southeastern parts of the United States, an area known as Tornado Alley. The United States experiences more tornadoes than any other country in the world. Tornadoes also appear in places such as South Africa, much of Europe (except most of the Alps), western and eastern Australia, New Zealand, Bangladesh, eastern India, Japan, the Philippines, and southeastern South America. Scientists and weather watchers can detect tornadoes using special radar tools like pulse-Doppler radar and by observing patterns such as hook echoes or debris balls.

Rating

See also: Research history of tornadoes

There are different ways to measure how strong a tornado is. The Fujita scale, and its updated version the Enhanced Fujita Scale, look at the damage tornadoes cause. The weakest tornadoes, rated F0 or EF0, might only knock down trees. The strongest, rated F5 or EF5, can tear buildings from their foundations and even affect tall skyscrapers. Other scales, like the TORRO scale and the International Fujita scale, also help describe a tornado's strength by looking at the damage it creates. Scientists also use tools like Doppler radar and photographs to learn more about tornadoes.

Etymology

The word tornado comes from the Spanish word tronada, which means 'thunderstorm'. This word has roots in Latin, where tonāre means 'to thunder'. The English spelling was influenced by the Spanish word tornado, which means 'to twist or turn'.

There is also a related wind phenomenon called a derecho, which is a widespread, straight-line wind, different from the concentrated area of a tornado. The word derecho also comes from Spanish, meaning 'straight'.

Definitions

A tornado is a violently rotating column of air that touches the ground and connects to a cloud. It is often seen as a funnel-shaped cloud. Not all funnel clouds become tornadoes, and sometimes tornadoes start as funnel clouds before touching the ground.

When a single storm creates multiple tornadoes, either one after another or at the same time, these are called a tornado family. If many tornadoes happen in a short time without a break, it is known as a tornado outbreak. A series of tornado outbreaks over several days in the same area is called a tornado outbreak sequence.

Main article: Funnel cloud

Characteristics

Tornadoes come in different sizes and shapes. Most look like a narrow funnel, a few hundred meters wide, with a small cloud of debris near the ground. Some small tornadoes, called landspouts, might only be a swirl of dust. Larger tornadoes can look like wide wedges stuck into the ground. As tornadoes lose strength, they can become thin and rope-like.

In the United States, tornadoes are usually about 500 feet across, but they can be much smaller or much larger. Some narrow tornadoes have damage paths only a few feet long, while huge wedge tornadoes can be over a mile wide. The average tornado travels about 5 miles on the ground, but some have traveled much farther. One famous tornado in 1925 traveled for 219 miles.

Life cycle

See also: Supercell

Tornadoes often come from big thunderstorms called supercells. These storms have spinning air high up and can create the most powerful tornadoes. When rain falls, it can pull the spinning air down towards the ground, starting the tornado.

As the spinning air gets closer to the ground, it forms a visible funnel. This funnel can cause damage when it touches the ground. The tornado grows strong for a while, but then weakens when cool air wraps around it, cutting off its supply of warm air. Even as it weakens, a tornado can still cause damage before it disappears. Sometimes, a storm can create new tornadoes one after another.

Types

Multiple vortex

Main article: Multiple-vortex tornado

A multiple-vortex tornado has two or more small funnels that spin around a central point. These funnels can cause extra damage along the main tornado’s path. They are often seen in big, strong tornadoes.

Waterspout

Main article: Waterspout

A waterspout is a tornado that forms over water. There are two kinds: fair weather waterspouts, which are weaker and common, and tornadic waterspouts, which are stronger and come from severe thunderstorms. Waterspouts usually form near places like the Florida Keys or the Adriatic Sea.

Landspout

Main article: Landspout

A landspout is a smaller tornado that forms without the big storm systems that create regular tornadoes. They look like tiny tornadoes and usually don’t last long, but they can still be powerful enough to cause damage.

Similar circulations

Gustnado

Main article: Gustnado

A gustnado is a small spinning column of air that forms near the edge of a thunderstorm’s outflow. It isn’t connected to a cloud and usually causes only minor damage.

Dust devil

Main article: Dust devil

A dust devil is a spinning column of air that forms on hot, clear days. It looks like a tiny tornado but isn’t strong enough to be one. Dust devils can sometimes cause damage.

Fire whirls

Main article: Fire whirl

Fire whirls are spinning columns of air that form near big fires. They aren’t usually as strong as tornadoes but can still cause damage.

Steam devils

Main article: Steam devil

A steam devil is a rare spinning column of air that forms from steam or smoke, like from a power plant’s smokestack. They spin slowly and aren’t very strong.

Intensity and damage

Tornadoes are rated by how much damage they cause, using scales like the Enhanced Fujita (EF) scale. An EF0 tornado might knock down trees, while a powerful EF5 tornado can rip buildings right off their foundations. These ratings help us understand how strong a tornado was based on the damage it left behind.

Most tornadoes in the United States are weak, with only a small percentage being very strong or violent. Strong tornadoes can sometimes be larger, but their most powerful winds might not always hit buildings or trees, which can make them harder to rate accurately. While violent tornadoes are rare outside areas like Tornado Alley, they can occur in many parts of the world.

Climatology

The United States has the most tornadoes of any country, mostly because of its special geography. North America stretches from warm tropical areas to cold arctic regions without big mountains blocking the air flow. This helps create the right conditions for tornadoes, especially in an area known as Tornado Alley in the central United States, which also extends into parts of Canada.

Tornadoes can happen anywhere in the world, but they are most common in the spring and least common in the winter. They usually happen in the late afternoon, between 3 pm and 7 pm local time. While most tornadoes are weak, they can sometimes be very powerful and cause a lot of damage.

Detection

Main article: Convective storm detection

In the mid-20th century, the United States began serious efforts to warn people about tornadoes. Before the 1950s, the only way to know about a tornado was if someone saw it. Now, weather radar helps give warnings before a tornado arrives. The first tornado warnings were issued in 1950, and by 1953, scientists learned that certain radar patterns, called hook echoes, are linked to tornadoes.

Today, most developed countries use weather radars to detect possible tornadoes. Doppler radar, used in the United States and some other places, can measure wind speed and direction from far away, helping experts spot rotation in storms that might lead to tornadoes. Trained storm spotters also play an important role. They watch storms closely and report what they see, which helps confirm whether a tornado is actually on the ground. Spotters are especially important because radar can sometimes miss details that a person watching the storm can see.

See also: Pulse-Doppler radar and weather radar

Extremes

The Tri-State Tornado, which happened on March 18, 1925 and affected parts of Missouri, Illinois, and Indiana, holds several tornado records. It had the longest path length at 352 km (219 miles) and lasted about 3 and a half hours.

One of the biggest tornado outbreaks was the 1974 Super Outbreak, which brought 148 tornadoes to a large area of the central United States and southern Ontario over two days in April 1974. Many of these tornadoes were very powerful.

Storms that create tornadoes can have very strong updrafts, sometimes faster than 240 km/h (150 mph). Debris from tornadoes can be lifted high into the storm and carried far away.

Safety

When a tornado warning is issued, it is important to have a plan and know where to go to stay safe. The best place to go is a basement or an inside room on the first floor of a strong building. In areas where tornadoes happen often, many buildings have special underground rooms called storm cellars that help protect people.

Countries with tornado warnings have weather services that tell people when a tornado might come. Weather radios can also give alerts for severe weather. If you are driving and see a tornado, it is best to stop your car far off the road and find a strong place to hide. If there is no strong building nearby, lying in a ditch is better than staying under a highway overpass, which can be very dangerous during a tornado.

Myths and misconceptions

Many old stories and beliefs about tornadoes are not true. For example, some people think a green sky means a tornado is coming, but this is not always the case. Another myth is that opening windows during a tornado will reduce damage, but this can actually make things worse.

It is also a common belief that hiding under a highway overpass can protect you from a tornado. However, this is very dangerous. Overpasses can make tornado winds even stronger, and they do not offer real safety. The safest place during a tornado is in a basement, preferably in a central room or under sturdy furniture. Remember, tornadoes can happen anywhere, even in cities, near rivers, or in mountainous areas.

Ongoing research

Main article: History of tornado research

Scientists have been studying tornadoes for many years, but there is still much they don’t fully understand. They know a lot about how thunderstorms and spinning air masses form, but they are still learning how these lead to tornadoes. Researchers are especially interested in how small spinning motions near the ground turn into tornadoes and what role different air movements play.

Scientists use many tools, such as special cameras, radar, and computers, to learn more about tornadoes. They also go out into the field to collect data when tornadoes are possible. Many groups, including universities and government agencies, work together to improve tornado predictions and understanding. There is still more to discover about how and why tornadoes form and behave the way they do.