11:32 am - Monday May 28, 2012

Tornado

A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider sense, to name any closed low pressure circulation. 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 less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).

Tornado Information

A tornado is “a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud”. For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. Scientists have not yet created a complete definition of the word; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes. Tornado refers to the vortex of wind, not the condensation cloud.

Tornado Facts

Here are some fun tornado facts:

  • The most powerful Tornadoes occur in the United States.
  • A typical tornado only lasts for a few minutes.
  • Every tornado has its own color, sound and shape.
  • You need to step on the pedal of a car pass 70 miles per hour to outrun the fastest tornadoes.
  • The chances that a tornado is a F5, the highest classification for a tornado on the F-scale, is less than 0.1%
  • Tornadoes have been reported in every state in the US and also in every season.
  • A Tornado can occur at any time, but most often between 3pm and 9pm.

Tornado Types

Tornadoes come in various sizes and can form in different locations. They can range in shape from narrow and rope-like, narrow or fat cylinders, or be cone or wedge-shaped. They also form in different situations. Below are some of the variations.

Supercell Tornadoes : Some of the most violent tornadoes develop from supercell thunderstorms. A supercell thunderstorm is a long-lived thunderstorm possessing within its structure a continuously rotating updraft of air. These storms have the greatest tendency to produce tornadoes, some of the huge wedge shape. The supercell thunderstorm has a low-hanging, rotating layer of cloud known as a “wall cloud.” It looks somewhat like a layer of a layer cake that hangs below the broader cloud base. One side of the wall cloud is often rain-free, while the other is neighbored by dense shafts of rain. The rotating updraft of the supercell is seen on radar as a “mesocyclone.”
The tornadoes that accompany supercell thunderstorms are more likely to remain in contact with the ground for long periods of time — an hour or more — than other tornadoes, and are more likely to be violent, with winds exceeding 200 mph.
Landspout : Generally weaker than a supercell tornado, a landspout is not associated with a wall cloud or mesocyclone. It may be observed beneath cumulonimbus or towering cumulus clouds and is the land equivalent of a waterspout. It often forms along the leading edge of rain-cooled downdraft air emanating from a thunderstorm, known as a “gust front.”
Gustnado : Weak and usually short-lived, a gustnado forms along the gust front of a thunderstorm, appearing as a temporary dust whirl or debris cloud. There may be no apparent connection to or circulation in the cloud aloft. These appear like dust devils.
Waterspout : A waterspout is a tornado over water. A few form from supercell thunderstorms, but many form from weak thunderstorms or rapidly growing cumulus clouds. Waterspouts are usually less intense and causes far less damage. Rarely more than fifty yards wide, it forms over warm tropical ocean waters, although its funnel is made of freshwater droplets condensed from water vapor from condensation - not saltwater from the ocean. Waterspouts usually dissipate upon reaching land. The following are “cousins” to the Tornado.
Dust Devils : Dry, hot, clear days on the desert or over dry land can bring about dust devils. Generally forming in the hot sun during the late morning or early afternoon hours, these mostly harmless whirlwinds are triggered by light desert breezes that create a swirling plume of dust with speeds rarely over 70 mph. These differ from tornadoes in that they are not associated with a thunderstorm (or any cloud), and are usually weaker than the weakest tornado.
Typically, the life cycle of a dust devil is a few minutes or less, although they can last much longer. Although usually harmless, they have been known to cause minor damage. They can blow vehicles off the road and could damage your eyes by blowing dust into them.
Firewhirls : Sometimes the intense heat created by a major forest fire or volcanic eruption can create what is known as a firewhirl, a tornado-like rotating column of smoke and/or fire. This happens when the fire updraft concentrates some initial weak whirl or eddy in the wind. Winds associated with firewhirls have been estimated at over 100 mph. They are sometimes called fire tornadoes, fire devils, or even firenadoes.

Tornado Causes

Tornadoes occur with thunderstorms. There are a couple of ways that they form. Most strong and violent tornadoes occur with supercell thunderstorms. Thunderstorms occur when warm moist air is forced upward (by the heat of the afternoon sun, a cold front, or other weather disturbance). If the atmosphere is unstable strong upward currents called updrafts lift the air until water vapor condenses forming clouds and precipitation. The falling precipitation causes a downward air current called a downdraft. So to have thunderstorms there must be 1) moisture 2) unstable air 3) something to lift the warm moist air up. But as I mentioned most tornadoes occur with a special storm type called a supercell. Supercells occur with a certain wind conditions. Winds that turn from south to west with height and/or increase rapidly with height (especially in the lowest several thousand feet of the atmosphere) cause the updraft in a thunderstorm to rotate. If the updraft is strong enough and the wind shear is strong enough, a tornado may occur. Supercells also produce large hail, strong winds and heavy rain.

Tornado Videos & Images

Here you can find latest video & images of famous tornadoes.

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