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What is a tornado?
According to the Glossary of Meteorology (AMS 2000), a tornado is "a violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud." Literally, in order for a vortex to be classified as a tornado, it must be in contact with the ground and the cloud base. Weather scientists haven't found it so simple in practice, however, to classify and define tornadoes. For example, the difference is unclear between an strong mesocyclone (parent thunderstorm circulation) on the ground, and a large, weak tornado. There is also disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes. It is well-known that a tornado may not have a visible funnel. Also, at what wind speed of the cloud-to-ground vortex does a tornado begin? How close must two or more different tornadic circulations become to qualify as a one multiple-vortex tornado, instead of separate tornadoes? There are no firm answers.

How do tornadoes form?
The classic answer -- "warm moist Gulf air meets cold Canadian air and dry air from the Rockies" -- is a gross oversimplification. Many thunderstorms form under those conditions (near warm fronts, cold fronts and drylines respectively), which never even come close to producing tornadoes. Even when the large-scale environment is extremely favorable for tornadic thunderstorms, as in an SPC "High Risk" outlook, not every thunderstorm spawns a tornado. The truth is that we don't fully understand. The most destructive and deadly tornadoes occur from supercells -- which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. [Supercells can also produce damaging hail, severe non-tornadic winds, unusually frequent lightning, and flash floods.] Tornado formation is believed to be dictated mainly by things which happen on the storm scale, in and around the mesocyclone. Recent theories and results from the VORTEX program suggest that once a mesocyclone is underway, tornado development is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone (the occlusion downdraft). Mathematical modeling studies of tornado formation also indicate that it can happen without such temperature patterns; and in fact, very little temperature variation was observed near some of the most destructive tornadoes in history on 3 May 1999.

What direction do tornadoes come from? Does the region of the US play a role in path direction?
Tornadoes can appear from any direction. Most move from southwest to northeast, or west to east. Some tornadoes have changed direction amid path, or even backtracked. [A tornado can double back suddenly, for example, when its bottom is hit by outflow winds from a thunderstorm's core.] Some areas of the US tend to have more paths from a specific direction, such as northwest in Minnesota or southeast in coastal south Texas. This is because of an increased frequency of certain tornado-producing weather patterns (say, hurricanes in south Texas, or northwest-flow weather systems in the upper Midwest).

What is a multivortex tornado?
Multivortex (a.k.a. multiple-vortex) tornadoes contain two or more small, intense subvortices orbiting the center of the larger tornado circulation. When a tornado doesn't contain too much dust and debris, they can sometimes be spectacularly visible. These vortices may form and die within a few seconds, sometimes appearing to train through the same part of the tornado one after another. They can happen in all sorts of tornado sizes, from huge "wedge" tornadoes to narrow "rope" tornadoes. Subvortices are the cause of most of the narrow, short, extreme swaths of damage that sometimes arc through tornado tracks. From the air, they can preferentially mow down crops and stack the stubble, leaving cycloidal marks in fields. Multivortex tornadoes are the source of most of the old stories from newspapers and other media before the late 20th century which told of several tornadoes seen together at once.

Are big fat tornadoes the strongest ones?
No, Not necessarily. There is a statistical trend (as documented by NSSL's Harold Brooks) toward wide tornadoes having higher damage ratings. This could be related to greater tornado strength, more opportunity for targets to damage, or some blend of both. However, the size or shape of any particular tornado does not say anything conclusive about its strength. Some small "rope" tornadoes still can cause violent damage of EF4 or EF5; and some very large tornadoes over a quarter-mile wide have produced only weak damage equivalent to EF0 to EF1.
Where Do Tornadoes Come From?
How Fast Can A Tornado Go?
What Are The People Called Who
Study Tornadoes?
How Fast Do Tornadoes Move?
How Long Is A Tornado Usually On
The Ground?
What Direction Do Tornadoes Spin?
Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado.
Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado. Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado. Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado.
Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado.
We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.
We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.
We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.
People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.
People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.
People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.
We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.
We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.
We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.
Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.
Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.
Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.
Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise.
Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise. Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise. Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise.
Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise.
Where Do Tornadoes Occour?
Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. Tornadoes have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.
Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. Tornadoes have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. Tornadoes have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. Tornadoes have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.
Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. Tornadoes have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.
Has Every US State Had A Tornado?
Do Tornadoes Really Stay Away From
Gullies, Rivers, and Mountains?
Where Is Tornado Alley?
Where Is The Most Common "Birthplace"
For A Violent Tornado?
Yes, although some states have more tornadoes than others.
Yes, although some states have more tornadoes than others.Yes, although some states have more tornadoes than others.Yes, although some states have more tornadoes than others.
Yes, although some states have more tornadoes than others.
A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.
A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.
A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.
"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!
"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!
"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!
According to research done by Dr. Harold Brooks at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.
According to research done by Dr. Harold Brooks at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.According to research done by Dr. Harold Brooks at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.According to research done by Dr. Harold Brooks at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.
According to research done by Dr. Harold Brooks at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.
Tornado FAQs
How are tornadoes rated?
They are rated by how much damage and wind speed, using the Enhanced Fujita Scale. An EF-1 is the least damaging and EF-5 is the most damaging. Below is the current EF Scale.
Info courtesy of NOAA
Understanding the threat posed by tornadoes in the United States - particularly the threat of strong and violent tornadoes - is valuable knowledge to everyone, but especially to weather forecasters and emergency management people. Knowledge about long-term patterns helps us be better prepared for natural disasters and could also help scientists detect shifting patterns in severe weather events caused by climate change.