A tornado or twister is a violent, rotating column of air which typically has a speed ranging from 177 km/h to over 480 km/h. This devastating windstorm is usually characterized by its funnel-shaped cloud that extends toward the ground.

20,359 Questions

What causes tornadoes?

Tornadoes are caused by the interaction of weather systems, which create large thunderstorms (the most powerful and long-lived type is called a supercell). The winds created by the growth and motion of these storms may create vortices (funnel clouds) that can descend to reach the ground, and move along the ground as tornadoes.

The formation of tornadoes is complicated.

First, you need thunderstorms, then you need a condition called wind shear, in which the speed or direction of the wind changes with altitude. If the shear is strong enough it can essentially tilt a thunderstorm. This separates the updraft and downdraft of the thunderstorm, preventing them from interfering with one another. This allows the storm to become stronger and last longer.

Additionally, if the wind shear is strong enough it can start the air rolling in what is called horizontal vorticity. This horizontal vorticity can then be turned vertical by a thunderstorm's updraft. When this happens, the thunderstorm may start rotating. The rotation is especially strong in an updraft called a mesocyclone. If the storm intensifies rapidly enough, a relatively warm downdraft called a rear-flank downdraft or RFD can wrap around the bottom part of the mesocyclone. This can then tighten and intensify its rotation and bring it down to the ground to produce a tornado.

Meteorology and Weather
Hurricanes Typhoons and Cyclones

How are tornadoes and hurricanes similar?

Hurricanes and tornadoes are both natural disasters that produce powerful, destructive winds that spiral cyclonically inwards via low pressure (clockwise in the southern hemisphere, counterclockwise in the northern hemisphere).

Hurricanes have a calm, clear eye at the center of rotation and it is believed that many tornadoes have a similar feature.

Both have scales for rating intensity:

  • Tornadoes are rated on the Fujita scale from F0 to F5 based on damage, some countries, including the United States have upgraded to the Enhanced Fujita scale (EF0 to EF5).
  • Hurricanes are rated on the Saffir-Simpson scale from Category 1 to Category 5.

How are tornadoes formed?

Meteorologists still do not know exactly how tornadoes form, or why. But many facts are known.

Tornado Formation

Tornadoes almost always form in strong thunderstorms which develop along what is called a "dry line." A dry line is a boundary between warm, moist air and cooler, drier air which tries to slip over it. This causes a tremendous instability in the atmosphere, as warm air rises, and cooler air wants to sink. As the warmer, more humid air surges upward through the cooler air mass, water vapor condenses, causing huge cumulonimbus clouds.

The condensation of the water vapor also generates more (latent) heat, which causes the warm air, already rising, to rise even faster. In large cumulonimbus clouds, often over five miles high, there can be winds of over 70 miles per hour -- going straight up. But, as these streams of air go up, other streams of cooler air must come down. As these downward winds reach the earth, straight-line winds can go just as fast as the upward streams of air. You may have noticed in a thunderstorm that the first winds you feel are quite cool.

Meteorologists believe that where the upward and downward flow of winds meet, a horizontal (flat) area of spinning winds form, or a vortex lying sideways, so to speak. This is called horizontal vorticity. This process is greatly enhanced by strong wind shear, in which the speed or direction of the wind changes with altitude.Below this horizontal vortex, in certain places of the storm, the upward push of the warmer air is stronger, tending to "tilt" the vortex. As this process continues, they believe, the vortex is gradually changed from horizontal to vertical (up-and-down), and the storm may start rotating. .

As the vortex changes its orientation, it begins to act as a special kind of conduit for warm and cold air. Cold air descends, in the rotating winds that can be seen. But within the ring of rotating winds is an area of extreme low pressure; once again, caused by rising warm air, in an upward flow of tremendous speed. The rotation is especially strong in an updraft called a mesocyclone. If the storm intensifies rapidly enough, a relatively warm downdraft called a rear-flank downdraft or RFD can wrap around the bottom part of the mesocyclone. This can then tighten and intensify its rotation and bring it down to the ground to produce a tornado

The general principle can sometimes be seen in a draining sink. If you drain a sink with very still water, sometimes it just drains; nothing special happens. But if you give the water a little extra motion, you will see a spinning "funnel" form, directly above the sink drain. The mechanics are pretty much the same. Water is heavier than air. The air in the drain pipes wants to rise out, and the water wants to sink. The vortex that forms lets this happen faster.

More information

What is not known about how tornadoes form is why some giant thunderstorms produce tornadoes, and others, seemingly having the same characteristics, don't. Weather scientists are still studying what the differences may be, and trying to find a more exact understanding of how tornadoes form.

It is known that a dry line moves, generally, from the northwest toward the southeast. The warm air is usually moving from the southwest toward the northeast. It would be like two arrows crossing each other at right angles, with the "cold air" arrow on top and the "warm air" arrow on bottom. Meteorologists theorize that this crossing pattern adds to the development of a tornado, determining the direction of rotation (counterclockwise in the Northern Hemisphere), and determining where in a storm a tornado is most likely to form (the southeastern quadrant). Doppler radar has been very successful at predicting areas of likely tornadoes in storms, as a tornado will generally have a "signature" pattern on radar, resembling a sort of curlicue.

Scientists look at what does and doesn't happen in a storm, to try to understand more about why tornadoes form. It has been observed that there is not usually any rain near a tornado, although there may be heavy hail near one. It's also been noticed that there is heavier lightning around tornadoes. Some theorize that electrical charges may aid in the formation of a tornado, while others believe a tornado is the reason for the increased electrical charge. Some have theorized that even truck traffic on a fast highway can contribute to tornado formation, when the conditions are right, as a truck leaves a vortex of air behind it as it passes.

While no one yet knows exactly why a tornado forms, knowledge is growing every year. It is known what conditions have to be present, and it's likely that most of the current theories are pretty close to the truth. But dedicated scientists want to know more, and there are numerous scientific projects underway to try to understand tornadoes better, to aid in predicting them and saving lives.

Meteorologists and other scientists, as of 2009, still do not know exactly how tornadoes form, or why. But some facts are known.

Hurricanes Typhoons and Cyclones
Survival Tips

Where is the safest place to go during a tornado?

Generally speaking, you want to be as low to the ground as possible during severe tornado conditions. A basement is ideal, as particularly powerful tornadoes can tear buildings apart. If you don’t have access to an underground space, being near the center of the building is the next best plan, staying away from any windows, as flying debris is one of the greatest dangers during these storms. If your interior bathroom has a bathtub, that can also be a sturdy place to stay safe.

Hurricanes Typhoons and Cyclones

What is the difference between a hurricane and a tornado?

Hurricanes and tornadoes are both damaging windstorms, but they are very different phenomena. One is a large weather system and the other is an isolated weather event. A hurricane is a huge airmass that can be more than 1000 miles across, while a tornado is seldom more than 1 mile across, and often much less.


A hurricane (also known as a cyclone or typhoon) is a very large,swirling storm with strong winds and heavy rains. It consists of an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. These cyclonic circulations of wind and clouds can sometimes, but not always, lead to a storm characterized by a low pressure center and numerous thunderstorms that produce strong winds and flooding rain. They can only form over warm water with minimal wind shear, but often make landfall at some point as they move across the ocean. While much of the damage caused by hurricanes is from high winds, equally dangerous is its storm surge, which can flood entire cities, killing large numbers of people.


  • Are hundreds of miles wide.
  • Form only over warm ocean water.
  • Last for days and sometimes well over a week.
  • Produce rain and flooding in addition to powerful winds.
  • Are independent, self-sustaining storm systems.
  • Have winds ranging from 74 to about 200 mph


A tornado is a swirling column of wind that moves across the ground in a relatively narrow path. It consists of a violent, dangerous, rotating column of air which extends from a cloud to the ground. 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. They can demolish entire neighborhoods in a matter of a few seconds to a few minutes.

Tornadoes form from thunderstorms called supercells and reach toward the ground as they develop. Most tornadoes last a few minutes and never more than a few hours. Some last just a few seconds. Most tornado deaths are from flying debris.


  • Are rarely over a mile wide
  • Usually form over land
  • Usually last minutes, rarely a few hours
  • Cause damage via wind and debris
  • Are dependent on a large storm to develop and keep going
  • Have winds ranging from 65 to about 300 mph
  • Often have a condensation funnel.

In summary:

  1. Hurricanes form over warm ocean water as tropical depressions, and weaken rapidly over land. Tornadoes normally form over land from mesocyclones.
  2. Hurricanes are hundreds of miles wide while tornadoes are typically a few dozen yards wide, getting up to two-and-a-half miles wide at most.
  3. A hurricane usually lasts a few days while a tornado cannot last more than a few hours, and some last just a few seconds.
  4. Hurricanes can produce large waves and storm surge, tornadoes, waterspouts and flooding rains. A tornado can be accompanied by these but does not directly cause them.
  5. The strongest tornadoes have faster winds than the strongest hurricanes.

What is the most devastating tornado ever recorded in the United states?

The most devastating tornado in U.S. history was the Tri-State tornado of March 18, 1925. This tornado tore a 219 mile long damage path across part of Missouri, Illinois, and Indiana, killing 695 people and destroying over 15,000 homes.


How do tornadoes disappear?

What causes tornadoes to dissipate is not fully understood, but it is believed that cold thunderstorm outflow undercuts the parent circulation (mesocyclone) that drives the tornado, cutting of the warm air that drives the thunderstorm, causing it to weaken to the point that it can no longer sustain a tornado.


What does density have to do with tornadoes?

Density is not directly related to tornadoes, but it does play a role in how they form.

Cold air is denser than warm air and dry air is denser than moist air. When a dry and moist or a warm and cold air mass collide the less dense air mass is forced upwards and the moisture in it condenses. It is by the process that the thunderstorms that spawn tornadoes usually form.

Thunderstorms and Lightning

Can an isolated thunderstorm become a tornado?

A thunderstorm does not become a tornado. It can produce one.

Yes, though. If the atmosphere is unstable enough and there is enough low-level wind shear, then an isolated storm can produce a tornado.


Can a waterspout go over land?

A waterspout can transition from water to land but becomes a tornado as long as it is touching land; if it is not touching the ground it would be called a "funnel cloud".

Hurricanes Typhoons and Cyclones

What is worst cyclone or tornado?

A cyclone is simply a large-scale area of low atmospheric pressure with closed cyclonic circulation. They may bring thunderstorms but are not necessarily severe. However, hurricanes and typhoons, which are a type of cyclone, are generally worse than tornadoes.

Tornadoes can cause more severe damage on a local scale than cyclones of any type can, but their affects are over a much smaller area.


How fast of wind speed does it take to start a tornado?

There is no set wind speed to that qualifies as a tornado, though different scales have minimum estimates ranging from 40mph to 65 mph.

Hurricanes Typhoons and Cyclones

Which is deadlier a Tornado or a Hurricane?

A hurricane can inflict a higher death toll than a tornado largely because it affects a much bigger area.

Also, there are more ways that hurricanes can kill.

Most tornado deaths result from flying or falling debris, and some other result from people being thrown.

Hurricanes can cause deaths be similar means, but most hurricane deaths result from flooding caused either by the storm surge or heavy rain. The rainfall from hurricanes can also cause deadly landslides.

However, tornadoes are more violent than hurricane and can cause more fatalities per square mile that they affect.

Statistically, however, tornadoes kill more people in the United States than hurricanes.

Word Games

What are some descriptive words for tornadoes?

scary, frightening, powerful, dangerous, destructive, deadly


Where was the most powerful tornado?

The most powerful winds every recorded in a tornado were 301 mph. This measurement was taken from the F5 tornado that occurred near Oklahoma City on May 3, 1999.

However, this may not have been the strongest tornado that ever occurred. but the most destructive and highest winds in the world Other tornadoes may have been stronger but were never recorded as such because no measurements were taken.


What kinds of clouds form tornadoes?

Technically, it's a process of multiple cloud levels. Tornadoes form from Funnel Clouds, which form from Wall Clouds, which form along the base of Cumulonimbus clouds. So you start with a Cumulonimbus cloud (also known as a thunderhead or thunderstorm cloud) and a wall cloud can form along the base it. A wall cloud is a lowered base of a storm that is rotating.

Attached to several wall clouds, especially in moist environments, is a tail cloud,which is just a band of clouds that resemble a tail. Most often the wall clouds' movement will be horizontal and in other clouds may be seen as moving in toward the wall cloud. There is also sometimes something called a collar cloud atop the wall cloud which is a band of clouds circling over it. Wall clouds will usually will slope inward, or toward the precipitation area.

From that wall cloud, a smaller lowering of rotation can occur, often in a funnel shape, known as a funnel cloud. If that funnel cloud reaches the ground, it's known as a tornado.


Is the bath a safe place to hide during a tornado?

Yes. A bathtub is the next best thing to a storm cellar or basement. People taking shelter in bathtubs have survived even when the house was completely destroyed.


How are tornadoes measured and tracked?

it used to be measured by the Fujita scale but now the enhanced fujita scale And they track it down by

  1. weather radar
  2. storm watching mostly by train spotters
  3. storm chasing
  4. using weather instruments
Meteorology and Weather
The Sun

What is heat from the sun called?

That would be called Solar Radiation.

Oceans and Seas
How To

How tornadoes happen at sea?

A Tornado At Sea would be Called a waterspout.

There are two types of waterspout.

Tornadic waterspouts form the same way as normal tornadoes do, only the form on or move onto water. For information on this, see the ling to the related question below.

The second and more common type of waterspouts are fair weather waterspouts which are typically weaker than ordinary tornadoes.

They typically form from developing thunderstorms over relatively water mater. They start when the water is warmer than the air above it and warms the layer just above the surface. This warm, moist air will tend to rise, and, if there is surface-level vorticity in the area may start to rotate. As this spinning updraft matures it can connect to the updraft the feeds a developing storm above it and further intensify to from a waterspout.


How far can a tornado travel?

It varies widely.

The average tornado travels 5 miles before dissipating.

But damage path may range from just a few yards long to over 100 miles.

The longest distance on record that a tornado traveled was 219 miles.


How is the strength of a tornado determined?

Tornado intensity is determined by damage, which is used to estimate wind speed. These wind speed estimates are used to sort a tornado into one of six categories from EF0 to EF5.


Can a tornado hit thunder bay on?

Yes. Tornadoes do occur in that region.


Is the core of a tornado safe?

No. The core of a tornado is the area in which the strongest winds occur. Although the center itself may be calm in some tornadoes, you would still have to get through the intense winds of the tornado both going in and going out. Additionally, this eyelike structure is much smaller than the eye of a hurricane and would not likely be over any particular spot for more than a few seconds.


How does twister start?

The process of tornado formation starts when rolling air called wind shear gets taken into the updraft of a thunderstorm. This turns the storm into a supercell, a storm with a strong, rotating updraft called a mesocyclone. Under the right conditions a downdraft can descend from the back of the storm, wrap around the mesocyclone, and force it into a tighter more intense vortex: the tornado itself.


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