Tornado Alley

Tornado Alley is located in the mid and Eastern states of the USA. Tornado Alley is the most common area for tornadoes the United States due to the warm, moist air from the tropical south meeting the cold dry Arctic air from the north. the area stretches from West-Texas to North-Dakota. It is 1600 kilometres from north to south and 950 kilometres from east to west. Tornado alley's large and flat area of land, combined with the collision of air currents from the north and south create the perfect conditions for tornadic thunderstorms.

Tornado Life Cycle

Supercell
Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain a concentrated area of rotation low in the atmosphere, this rotation causes the development of tornadoes. Tornadoes that form from the supercell often follow the same life cycle. The supercells within a thunderstorm begin tornadoes with an area of rapidly descending air follow known as Rear Flank Downdraft (RFD). This RFD accelerates in its decent dragging the rotation in the atmosphere with it, thus creating the start of a Tornado.

Formation
As the rotation of the cyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud becomes a tornado within minutes of the RFD reaching the ground

Maturity
From the start the tornado has a good source of warm, moist atmosphere to power it, so that it can grow to its mature stage. This can last anywhere from a few minutes to more than an hour. During its mature stage the tornado often causes the most damage. In rare cases the Tornado can be more than one mile across. During the mature stage the RFD becomes a cool surface of winds and begins to wrap around the tornado, cutting off the warm air which feeds the it.

Dismise
As the RFD surrounds and chokes off the tornado's air supply, the vortex begins to weaken, and becomes thin. This stage often lasting no more than a few minutes, after which the tornado fizzles. The shape of the tornado is now determined by the winds of the storm above and can be blown into fantastic patterns. Even though the tornado is dieing, the tornado is still capable of causing damage. The storm is contracting into a thin tube and winds can increase. intense supercells tornadoes can develop cyclically. As the first tornado dissipate, the storm's inflow may be concentrated into a new area closer to the center of the storm. If a new cyclone develops, the cycle could start all over again, producing new tornadoes. Occasionally, the first and second cyclone produce a tornado at the same time.

Though this is a widely-accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as land spouts, long-lived tornadoes, or tornadoes with multiple vortexes, however, most tornadoes follow a pattern similar to this one.

Some More Facts

The word or name Tornado derived from the Spanish word for thunderstorms, Tronada. A tornado is often is referred to a twister or a cyclone. The Glossary of Meteorology defines a tornado as "a violently rotating column of air, in contact with the ground."


Locations
Every Continent, other then Antarctica have had reports or evidence of Tornadoes, although the United States contain the most Tornadoes. This is because of North Americas unique Geography which extends from the tropical South to the Arctic North forming high and low pressures traveling up and down the Continent without mountain rage to the block the air currents. The Rocky Mountains block moisture and atmospheric flow, allowing drier air at mid-levels of the troposhere, and causing cyclogenesis downstream to the east of the mountains. The desert Southwest also feeds drier air and the dry line, while the Gulf of Mexico fuels abundant low-level moisture. The unique atmospheres of this area of the world allows for collisions of the warm and cool air which causes the majority of tornadoes throughout USA. Tornado Alley is the worst affected area.

Tornado Documentaries

Storm Chasers

Storm Chasers i a series on the Discovery Channel about tornadoes. the series consists of a team of scientists, meteorologists and film makers eager to find out what really happens inside of a tornado using the best and most advanced equipment available to them. A Vehicle called the TIV (tornado Intercept Vehicle) designed, created and controlled by extreme film maker Sean Casesy allows himself and the scientists to enter a tornado and record its features from inside, if they can catch it on the ground. with the help from another vehicle, the DOW, Doppler radar which records and predict the location tornadoes from a distance using radar.

How do Tornadoes Form?

1) A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.

2) Rising warm air currents within the thunderstorm pulls the rotating air from horizontal to vertical, into the storm itself. wind speeds increase and the area of rotation extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.

3) A lower cloud base can identify an area of rotation known as a rotating wall cloud. This area is often nearly rain-free, this is because the moisture in the air becomes caught in the rotating winds. The rain often falls behind the rotaions.

4) Moments later a strong tornado develops in this area. Tennis ball-sized hail stones and damaging "straight-line" winds also occurred with this storm

http://www.nssl.noaa.gov/edu/safety/tornadoguide.html

Tornado Variations

Multiple Vortex
Multiple Vortex are tornadoes with with two or more spouts, columns of spinning air. Multiple Vortex's can occur in almost any tornado, however they are seen more commonly in large tornadoes, often making them more destructive.


Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type of tornado is most common along the front range of the Rocky Mountains, the Plains, and the Western States.
Tornadoes may appear nearly transparent until dust and debris are picked up.
Occasionally, two or more tornadoes may occur at the same time.


Satellite Tornadoes
Satellite Tornadoes are weaker tornadoes which form next to a larger tornado and orbits the larger tornado. often a satellite tornado is confused with a multi-vortex however a satellite has its own distinct column.


Land Spout
A land spout also known as a dust tube, are consitant with characteristics of a water spout in being a weaker tornado with a short life span. It forms without the force of a full storm.










Waterspout
Waterspouts are weak tornadoes that form over warm water, these are most common along the Gulf Coast and southeastern states. In the western United States, they occur with cold late fall or late winter storms, during a time when you least expect tornado development.
Waterspouts occasionally move inland becoming tornadoes causing damage and injuries.



Dust Devil
Dust devils are very similar to tornadoes in the sense that they are swirling columns of air yet a lot weaker then the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. These dust devils only occur in the better weather resulting in them not being classes as tornadoes.







Fire Whirl

Fire whirls occurs during forest fire from the updraft. The firle whirls are only considered a form of tornado when it reachs and join the clouds. Like dust devils fire whils are not as strong as weak thunder storm tornadoes however due to their fire content they can be just as destructive.

A Few Facts

Tornadoes happen when warm and cool airstream's collide, creating a rotating area of low atmospheric pressure. Air within a low pressure front has a natural tendency to rise and creates a strong upward draught. This draws in surrounding warm air from ground level, causing it to spin faster and faster.

In order for a vortex – a spiralling funnel of wind – to be classified as a tornado, it must be in contact with both the ground below and the storm cloud above. A tornado’s path is rarely more than 250m across, but can be as much as one mile wide.

There are 5 categories of Tornado, these categorise and scaled by the force and power of destruction combined with the speed of the winds within the vortex.

The intensity of a tornado is determined by the Fujita scale:

F1 Tornado - wind speeds between 73-112mph. Even the smallest tornadoes can peel slates from roofs and drive moving cars off the road.
F2 Tornado - wind speeds between 113-157mph. Roofs of some houses will begin to lift off and mobile homes in the tornado’s path would be demolished.
F3 Tornado - wind speeds between 158-207mph. Heavy trees will be uprooted and walls and roofs of solid buildings will be torn away like matchsticks.
F4 Tornado - wind speeds between 208-260mph. Locomotive engines and 40 tonne articulated trucks will be flung around like toys.

F5 Tornado - wind speeds between 261-318mph. Cars are flung like stones for hundreds of metres and entire buildings can be ripped from the ground. The force is similar to that of an atomic bomb.

http://www.discoverychannel.co.uk/earth/air/tornadoes/index.shtml

Predicting Tornadoes

Even though technology has improved vastly in weather prediction, it is still impossible to predict when a tornado is going to touch down. Meteorologists observe changes and development of air temperature, pressure and wind patterns. Atmospheric shifts within these elements can lead to 'tornadic' thunderstorms, however it is still far from possible to predict two days in advanced, it still relays on guess work.

The word or name Tornado derived from the Spanish word for thunderstorms, Tronada. A tornado is often is refered to a twister or a cyclone. The Glossary of Meteorology defines a tornado as "a violently rotating column of air, in contact with the ground."

Brief Breakdown and Intial Thoughts

Content - Tornado
Context - Discovery Channel Documentary

Research

The Science - Facts, Figures & Data:
- Weather patterns
- Living With Tornadoes
- Predicting Tornadoes
- The Prevention of Destruction
- The Aftermath- Different Cultures
- Richer and Poorer Cultures
- Difference between Tornadoes and HurricanesLook at Documentaries about Tornadoes and Hurricanes!

The Audience
Audiences for the Discovery Channel is vast, the Discovery channel has many spin-offs of its channel for more targeted audiences. What is my audience?

Bibliography and References

http://www.discoverychannel.co.uk/earth/air/tornadoes/index.shtml

http://www.discoverychannel.co.uk/earth/air/tornadoes/prediction/index.shtml

http://www.nssl.noaa.gov/edu/safety/tornadoguide.html

http://news.bbc.co.uk/1/hi/sci/tech/7533941.stm

http://www.torro.org.uk/TORRO/severeweather/tornadofaqs.php

http://www.fema.gov/hazard/tornado/index.shtm

http://amsglossary.allenpress.com/glossary/browse?s=t&p=34

http://www.stormeyes.org/tornado/SkyPix/chk2tors.htm

http://en.wikipedia.org/wiki/Tornado

http://library.thinkquest.org/C001472/neen/tornadoes/alley.content.html

http://geography.about.com/od/physicalgeography/a/tornado.htm

http://en.wikipedia.org/wiki/Fujita_scale

http://www.weatheronline.co.uk/reports/wxfacts/Doppler-radar.htm

http://www.usatoday.com/weather/wdoppler.htm