A tornado is a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Tornadoes occur in many parts of the world, including Australia, Europe, Africa, Asia, and South America.
Tornado Alley is a nickname invented by the media for a broad area of relatively high tornado occurrence in the central U.S. The most common and practical way to determine the strength of a tornado is to look at the damage it caused. A wall cloud that may produce a tornado usually exists for 10–20 minutes before a tornado appears. The rear flank downdraft (RFD) is a downward rush of air on the back side of the storm that descends along with the tornado.
What we do: NSSL is working to simulate storms that produce tornadoes in computer models to better understand how they form and behave. Every year at the National Weather Festival, tornado chasers from around the country display their weather-chasing vehicles at the Storm-chaser Car Show.
Objects like wood, chickens, horses, cows, cars and even people can be lifted by tornadoes and carried long distances.
If you hear that a tornado warning is in effect for your community, a tornado has been spotted and is very close by.
Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.
If you hear that there is a tornado watch for your community, you should follow the advice of adults nearby, listen to a weather radio or your local TV station, stay alert and prepare as though a tornado could be coming.
Twisters can occur at any time of year but spring and summer are considered tornado season around here. Fiction: Windows should be opened before a tornado approaches to equalize pressure and minimize damage. There are many good websites with tornado information, but also, many inaccurate and unreliable ones. Tornado formation is believed to be dictated mainly by things which happen on the storm scale, in and around the mesocyclone. There were multiple tornadoes with only short separation, but the survey erroneously classified them as one tornado. That is more unusual than it seems, because most video that seems to show tornadoes merging actually involves either one tornado, or one among multiple subvortices, going behind another.
To oversimplify this a bit, a tornado (or any other atmospheric vortex) is the most efficient way to move air from one part of the atmosphere to another on its size and time scale.
The Enhanced F-scale (simple table or detailed 95-page PDF) is a much more precise and robust way to assess tornado damage than the original. F1 through F5 were used in practice, with F0 attached for tornadoes of winds weaker than hurricane force. A tornado is considered "significant" if it was rated EF2 or greater on the Enhanced F scale, or at least F2 on the old F-scale.

Grazulis (1993) also included killer tornadoes of any damage rating in his significant tornado database.
It is important to know that those definitions are arbitrary, mainly for parsing out more intense tornadoes in scientific research. It may sound trite; but by far, the most important software in the tornado forecast process is within the human brain. Doppler radar signatures can tell warning meteorologists a great deal about a thunderstorm's structure, but usually can't see the tornado itself. A few hours later, despite the tiny odds of a repeat, the second tornado in five days directly hit the base.
By most measures, SPC (formerly SELS, NSSFC) has improved its tornado forecasting over the past few decades. There are many ways to objectively gauge forecast performance--for example, verifying tornado watches with tornado reports and both watch types by all severe reports.
The general trend from 1985 onward has been for a greater percentage of tornado watches to contain tornadoes, and for more significant (EF2-5) tornadoes to occur in watches and outlooks.
Killer tornadoes, those striking densely populated areas, or those generating reports of exceptional damage are given highest priority for ground surveys. Most of the time, this happens either with multiple-vortex tornadoes or very small, intense single-vortex tornadoes. Hurricanes tend to cause much more overall destruction than tornadoes because of their much larger size, longer duration and their greater variety of ways to damage property. We have some public domain images of typical examples of F0 through F5 tornado damage linked from this FAQ's F-scale page.
Otherwise, public-domain tornado damage pictures are scattered among the tornado-related historic news items of various National Weather Service websites.
Even when strongly gripping the girders (if they exist), people may be blown loose, out from under the bridge and into the open--possibly well up into the tornado itself. Whether or not the tornado hits, parking on traffic lanes is illegal and dangerous to yourself and others. Our office would like to print signs (universal symbol image type signs) similar to "emergency exit," "fire extinguisher," etc. Because wind is invisible, it is hard to see a tornado unless it forms a condensation funnel made up of water droplets, dust and debris. Various Tornado Alley maps look different because tornado occurrence can be measured many ways: by all tornadoes, tornado county-segments, strong and violent tornadoes only, and databases with different time periods. The most destructive and deadly tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone.
In 1966, a tornado lifted a car into the air and dropped it on top of a 70-foot building – both passengers survived.
The Enhanced Fujita (EF) scale is a tool used by meteorologists to estimate the wind speeds of a tornado (the scale was called the Fujita scale until 2007.) After a tornado hits, scientists assess the damage created by their winds.
In the late 1980’s, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000-foot mountain.

There is a statistical trend (as documented by NSSL's Harold Brooks) toward wide tornadoes having higher damage ratings. Since official tornado records only date back to 1950, we do not know the actual average number of tornadoes that occur each year. A tornado is created by a giant thunderstorm (called a supercell) that has plenty of warm air rising up into the thundercloud.
The National Weather Service will usually announce a tornado watch before a tornado warning. During a tornado warning, you should put as many walls as you can between you and the tornado. Plus, tornado spotting and reporting methods have changed a lot over the last several decades.
The EF-Scale takes into account more variables than the original Fujita Scale (F-Scale) when assigning a wind speed rating to a tornado, incorporating 28 damage indicators such as building type, structures and trees. Recent theories and results from the VORTEX2 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. Tornadoes that do very little damage to buildings and outdoor structures are lowest on the scale. A tornado warning means that a tornado has been spotted, or that a rotating cloud that can lead to a tornado has been seen on Doppler radar by meteorologists. 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. For example, an EF-0 tornado – the weakest rating – can cause damage to the side of houses or rip off window shingles.
Most tornadoes occur in a central area of the country called Tornado Alley, which includes parts of Texas, Oklahoma, Colorado, Kansas, Nebraska and South Dakota (Texas receives more tornadoes than any other U.S. Even though a mall has walls, it also has a large roof that could collapse during a tornado, and a lot of objects that could be picked up and blown at you by the tornado’s wind. The benefits of this extend into many areas, including: improving building codes for resistance against most tornadoes (since most are weak anyway), the insurance and re-insurance industries, construction designs and practices, and comparisons of tornado damage with their weather situations and radar signatures (for improved watches and warnings).
Some communities even have certified tornado shelters or “safe rooms.” You might want to find a “safe room” in your house – ask your parents to help. An F5 tornado rated years ago is still an F5, but the wind speed associated with the tornado may have been somewhat less than previously estimated. The EF scale uses only estimates wind speeds, since the actual wind speeds inside a tornado cannot be measured. Worth has compiled a very detailed study of several such violent tornado disaster scenarios in the Metroplex, which could be adapted to other major metro areas as well.

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  1. 13.03.2014 at 14:13:25

    And I agree, do use the Datrex tends.

    Author: Britni
  2. 13.03.2014 at 18:11:29

    American nation with our brain power is particularly liable to mutations which the word and might be all.

    Author: TuralGunesli