Tornadoes form when strong winds within thunderstorms cause water vapor in the air to condense into a funnel cloud. They range in severity from weak land spouts to catastrophic tornadoes over 300 mph wide. Storm chasers carefully study weather data to track conditions favorable for tornado formation and document tornadoes. Safety tips include seeking shelter in interior rooms on the lowest floor of sturdy buildings and protecting your head and body when a tornado threatens.

1. Lindsay SchulzEducation 373Inquiry #3/4Tornadoes

2. TornadoesTornadoes are the most powerful, unpredictable and destructive weather systems on Earth. The National Weather Service defines a Tornado as a violently rotating column of air in contact with the earth’s surface (land or water) and commonly associated with a severe thunderstorm.

3. QuestionsWhat causes tornadoes?Are there different severities?How do people track tornadoes?What are some jobs that involve tornadoes?Where are tornadoes most likely to happen?What are some safety precautions?

4. CausesA tornado generally occurs when high winds within a low pressure system (such as a thunderstorm) cause water vapor in the air to condense in to a condensation funnel cloud. Many less severe tornadoes are not even visible to the human eye. Major tornadoes usually become more visible when the strong winds within the funnel lift up dirt and debris off the Earth’s surface. The average tornado has maximum wind speeds of about 112 mph or less, measures around 250 feet in width and travels approximately one mile before falling apart. Some of the most catastrophic tornadoes in recorded history have had winds in excess of 300 miles an hour (twice that of a category 5 hurricane), have measured more than 2 miles in girth, and have carved devastating paths of destruction miles and miles in length.

5. Types of TornadoesTornadoes are generally classified as either aland spout -- a tornado on landwater spout -- a tornado that forms over watergustnado -- a small tornado caused by a strong downburst of wind from a thunderstorm

6. How Tornadoes work…Tornadoes don't just pop into existence -- they develop out of thunderstorms, where there's already a steady, upward flow of warm, low-pressure air to get things started. It's kind of like when a rock concert erupts into a riot. Conditions were already volatile; they merely escalated into something even more dangerous.

7. Thunderstorms…Thunderstorms themselves form like many other clouds: A warm, moist air mass rises and cools, causing the water vapor to condense into clouds.However, if the updraft continues, this cloud mass will continue to grow and rise 40,000 feet (12,192 m) or more up into the troposphere, the bottommost layer of the atmosphere that we live in. A typical thunderstorm cloud can accumulate an enormous amount of energy. If the conditions are right, this energy creates a huge updraft into the cloud, but where does the energy come from?

8. Thunderstorms…CloudsClouds are formed when water vapor condenses in the air. This change in physical state releases heat, and heat is a form of energy. A good deal of a thunderstorm's energy is a result of the condensation that forms the cloud. Every gram of water condensed results in about 600 calories of heat -- and another 80 calories of heat per gram of water results from freezing in the upper atmosphere. This energy increases the updraft temperature, as well as the kinetic energy of upward and downward air movement. The average thunderstorm releases around 10,000,000 kilowatt-hours of energy -- the equivalent of a 20-kiloton nuclear warhead.

9. Thunderstorms…In supercell thunderstorms, the updrafts are particularly strong. If they are strong enough, a vortex of air can develop just like a vortex of water forms in a sink.This precursor to the tornado is called a mesocyclone, and is typically 2 to 6 miles wide. Once a mesocyclone forms, there's a roughly 50 percent chance that the storm will escalate into a tornado in around 30 minutes.

10. Tornadoes…Some tornadoes consist of a single vortex, but other times multiple suction vortices revolve around a tornado's center. These storms-within-a-storm may be smaller, with a diameter of around 30 feet, but they experience extremely powerful rotation speeds.The tornado reaches down out of a thundercloud as a huge, swirling rope of air. Wind speeds in the range of 200 to 300 mph aren't uncommon. If the vortex touches ground, the speed of the whirling wind (as well as the updraft and the pressure differences) can cause tremendous damage, tearing apart homes and flinging potentially lethal debris.

11. Tornadoes…The tornado follows a path that is controlled by the route of its parent thundercloud, and it will often appear to hop. The hops occur when the vortex is disturbed. You've probably seen that it is easy to disturb a vortex in the tub, but then it will reform. The same thing can happen to a tornado's vortex, causing it to collapse and reform along its path.Smaller tornadoes may only thrive for a matter of minutes, covering less than a mile of ground. Larger storms, however, can remain on the ground for hours, covering more than 90 miles and inflicting near continuous damage along the way.

12. Tornadoes…At this point, you might be wondering just how tornadoes eventually dissipate. Scientists still debate exactly how these deadly storms die, but one of the prime suspects is none other than the parent thunderstorm: the rotating mesocyclone. Tornadoes need instability and rotation. Disrupt the airflow, take away its moisture or destroy its unstable balance of hot and cold air, and it can't function.Often, a tornado will die because the cold outflow of air from falling precipitation upsets the balance.

13. Tornado Ratings…Tornadoes are among the most dangerous storms on Earth and, as meteorologists strive to protect vulnerable populations through early warning, it helps to classify storms by severity and potential damage.Tornadoes were originally rated on the Fujita Scale, named for its inventor, University of Chicago meteorologist T. Theodore Fujita. The meteorologist created the scale in 1971 based on the wind speed and type of da­mage caused by a tornado. There were six levels on the original scale.

14. ScaleF 0: Wind speed: 40 - 72 (64 - 116)Possible Damage: Light damage: Tears branches from trees; rips shallow-rooted trees from the ground; can damage signposts, traffic signals and chimneys.F 1:Wind speed: 73 – 112 (117 - 180)Possible Damage: Moderate damage: Roofing materials and vinyl siding can be displaced; mobile homes are highly vulnerable and can easily be knocked from the foundation or toppled; motorists can be sent careening off road and possibly flipped over.F 2:Wind speed: 113 - 157 (181 - 253)Considerable damage: Well-established trees are easily uprooted; mobile homes are decimated; entire roofs can be ripped off houses; train cars and trucking hauls are knocked over; small objects become dangerous missiles

15. Scale…Cont. F 3: Wind speed: 158 - 206 (254 - 332)Possible damage: Severe damage: Forests are destroyed as a majority of trees are ripped from the ground; entire trains are derailed and knocked over; walls and roofs are torn from housesF 4:Wind speed: 207 - 260 (333 - 418)Possible damage: Devastating damage: Houses and other small structures can be razed entirely; automobiles are propelled through the air.F 5:Wind speed: 261 - 318 (419 - 512)Incredible damage: Cars become projectiles as they are hurled through the air; entire houses are completely destroyed after being ripped from the foundation and sent tumbling into the distance; steel-reinforced concrete structures can be seriously damaged.

16. Storm ChasersStorm chasing isn't nonstop action and danger. It's actually a very methodical practice that requires lots of time spent studying weather data, driving, waiting and more driving. Storm chasers can spend 12 hours or more driving around and still not see a tornado of any kind. Byron Turk, navigator for the Discovery Channel's Storm Chasers series, describes the process like this:We find the storm hopefully before it gets dark, and hopefully it produces a tornado, and hopefully there are roads to it. Lots of decisions need to be made on how the supercell is doing, whether another one is more worthwhile, more data comes in and it's just a constant process of making the right decision over and over again. Hopefully.

17. Storm Chasers…contd.Before bed and first thing in the morning, storm chasers check weather reports from the National Weather Service, looking for favorable tornado conditions. Cold air at high altitudes with warm air close to the ground is a promising sign, along with wind shear, or winds at different altitudes blowing in different direct. Areas where cool air masses collide with warm air masses are also tornado spawning grounds. After analyzing the weather data, the chasers select a likely location. Then they hop into their chase vehicle and start driving.

18. Safety TipsLook & Listen for ...large hail, heavy rain, strong winds, frequent intense lightning ...bulge with a rotary motion at the base of the thunderstorm cloud ...loud roar like the sound of a jet or train. Seek Safe ShelterA basement is best. Otherwise choose ground-floor center rooms surrounded by other rooms. Never choose upstairs locations because tornadic wind speeds increase with height above the ground.Choose rooms on the north and east sides of your shelter if no interior rooms are available. Stay near the innermost walls. Avoid rooms on the south and west, because tornados usually travel from southwest to northeast.Choose a small closet or bathroom, because small rooms are less susceptible to collapse. Take shelter within the bathtub if there are no glass tub enclosures or large mirrors nearby.How to Protect Yourself and Your FamilyStay calm.Seek shelter IMMEDIATELY!Keep a portable TV/radio and flashlight in your shelter.Wear shoes to protect your feet from broken glass and other debris left by the storm.Protect head and chest- crouch, face to floor, hands behind head.Cover yourself with blankets, pillows or coats.Hide under sturdy furniture.Avoid candles, gas lanterns and oil lamps.In schools and offices: seek designated shelter in interior rooms or hallway's on ground floor, or lowest floor possible. Avoid auditoriums and gymnasiums.In shopping malls, seek the smaller interior shops on the ground floor.In shopping centers, avoid large open rooms as well as the south and west walls.Evacuate mobile homes and vehicles! Seek shelter in substantial structure, ditch or culvert.

19. Tornado Whereabouts…Tornadoes are produced by large (supercell) thunderstorms that often grow to over 40,000 feet. Mouse over the different regions of the continental United States on the map below to see the average number of tornadoes per year.United States Map

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21. Resourceshttp://www.livescience.com/topic/tornadoeshttp://www.howstuffworks.com/tornado.htmhttp://www.fema.gov/kids/tornado.htmhttp://www.weatherwizkids.com/weather-tornado.htmhttp://eo.ucar.edu/webweather/tornado.html#tornadochaos