World Wind Tour 2002

1. World Wind Tour 2002 Today you will explore the development and facts of tornadoes. By: Chad Lafferty

2. Tornadoes come in many shapes and sizes.Here are a few examples of various types of tornadoes.

3. Tornado FormationAlthough the the full details of how tornadoes form are not well known, they generally form in a huge, rotating thunderstorm called a super cell. Super cell thunderstorms form where cold, dry, polar air meets warm, moist, tropical air. When this happens the warm updraft punches through the overlying, stable layer and continues upward into a zone of cool, dry air. The resulting instabilities produce powerful vortex motions, the lifeblood of tornadoes. Tornadoes generally form in a part of the super cell called a mesocyclone. A mesocyclone draws energy into the storm, helping the storm to last for hours.

4. Tornado FormationThe funnel clouds that are the most easily recognizable parts of a tornado usually seem to descend from the cloud base. This does not mean that the vortex is descending from the cloud base, rather the vortex already extends from inside the clouds all the way down to the ground. The "descent" of the funnel cloud is usually caused when the air pressure inside the vortex drops due to increased wind speed. This drop in air pressure causes the ambient moisture in the air to condense--which is what you see. Moisture in the atmosphere condenses at a certain temperature and pressure combination, called the dewpoint.

5. Tornado FormationThis is a fairly typical temperature/dewpoint versus height graph.

6. Tornado FormationIn general, in the vortex of a tornado, the pressure is fairly constant along the entire height, but the temperature is usually higher near the ground than near the top of the vortex. As the pressure inside the vortex drops, the moisture condenses, beginning at the top of the vortex, where the temperature is lowest and continuing downwards, thus the impression that the funnel cloud is "descending." Sometimes, however, the temperature is warmer near the top of the vortex than near the ground, which causes the funnel cloud to "ascend" to the cloud base.

7. Tornado FormationTypically, the only indication of a pending tornado is the presence of a hook echo seen on conventional radar. Hook echoes generally signify the presence of rotation in a storm, however, not all storms that return hook echoes produce tornadoes. This picture, inside the blue box, is a hook echo taken from a land-based radar.

8. Animation of a TornadoClick on the movie icon below to view a simulation of a developing tornado.

9. Tornadoes come in seven different categories.Explore each of the seven Fujita Scale categories below and once you have learned about each one, continue the slide show by clicking the next button. F0 F1 F2 F3 F4 F5 F6

10. F0 • Intensity Phrase: Gale Tornado • Wind Speed: 40-70 mph • Type of Damage Done: Some damage to chimneys; breaks branches off trees; pushes over shallow- rooted trees; damages sign boards • Here is a picture of an F0 tornado

11. F1 • Intensity Phrase: Moderate Tornado • Wind Speed: 73-112 mph • Type of Damage Done: The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the Here is a picture of an F1 tornado roads; attached garages may be destroyed

12. F2 • Intensity Phrase: Significant Tornado • Wind Speed: 113-157 mph • Type of Damage Done: Considerable damage. Roof torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated • Here is a picture of an F2 tornado

13. F3 • Intensity Phrase: Severe Tornado • Wind Speed: 159-206 • Type of Damage Done: Roof and some walls torn off well constructed houses; trains overturned; most trees in forest uprooted • Here is a picture of an F3 tornado

14. F4 • Intensity Phrase: Devastating Tornado • Wind Speed: 207-260 mph • Type of Damage Done: Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large Click on the movie icon to missiles generated view video shot of an F4 tornado

15. F5 • Intensity Phrase: Incredible Tornado • Wind Speed: 261-318 mph • Type of Damage Done: Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel reinforced concrete Here is a picture of an F5 tornado structures badly damaged

16. F6 • Intensity Phrase: Inconceivable Tornado • Wind Speed: 319-379 mph • Type of Damage Done: These winds are very unlikely. Missiles, such as cars and refrigerators (No pictures are available would do serious for this magnitude of secondary damage that tornado because one has could not be directly never been recorded or identified as F6 damage. observed.) If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern.

17. Tornado Safety Tips Before a Tornado Occurs During a Tornado After a Tornado

18. Tornado Safety Tips -Conduct tornado drills each tornado season. Designate an area in the home as a shelter, and practice having everyone in the family go there in response to a tornado threat. -Discuss with family members the difference between a "tornado watch" and a "tornado warning."

19. Tornado Safety Tips • Have disaster supplies on hand: • Flashlight and extra batteries • Portable, battery-operated radio and extra batteries • First aid kit and manual • Emergency food and water • Non-electric can opener • Essential medicines • Cash and credit cards • Sturdy shoes

20. Tornado Safety Tips Develop an emergency communication plan In case family members are separated from one another during a tornado (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together. Ask an out-of-state relative or friend to serve as the "family contact." After a disaster, it's often easier to call long distance. Make sure everyone in the family knows the name, address, and phone number of the contact person.

21. Tornado Safety Tips Tornado Watches and Warnings A tornado watch is issued by the National Weather Service when tornadoes are possible in your area. Remain alert for approaching storms. This is time to remind family members where the safest places within your home are located, and listen to the radio or television for further developments. A tornado warning is issued when a tornado has been sighted or indicated by weather radar.

22. Tornado Safety Tips When a tornado warning is issued, the city will alert the community by sounding the city’s emergency sirens. An example of a tornado siren is below. Click on the speaker icon below to listen.

23. Tornado Safety Tips Mobile Homes Mobile homes are particularly vulnerable. A mobile home can overturn very easily even if precautions have been taken to tie down the unit. When a tornado warning is issued, take shelter in a building with a strong foundation.If shelter is not available, lie in ditch or low-lying area a safe distance away from the unit.

24. Tornado Safety Tips • Tornado Danger Signs • Learn these tornado danger signs: • An approaching cloud of debris can mark the location of a tornado even if a funnel is not visible. • Before a tornado hits, the wind may die down and the air may become very still. • Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

25. Tornado Safety Tips • If at home: • Go at once to a windowless, interior room; storm cellar; basement; or lowest level of the building. • If there is no basement, go to an inner hallway or a smaller inner room without windows, such as a bathroom or closet. • Get away from the windows. • Go to the center of the room. Stay away from corners because they tend to attract debris. • Get under a piece of sturdy furniture such as a workbench or heavy table or desk and hold on to it. • Use arms to protect head and neck. • If in a mobile home, get out and find shelter elsewhere.

26. Tornado Safety Tips • If at work or school: • Go to the basement or to an inside hallway at the lowest level. • Avoid places with wide-span roofs such as auditoriums, cafeterias, large hallways, or shopping malls. • Get under a piece of sturdy furniture such as a workbench or heavy table or desk and hold on to it. • Use arms to protect head and neck.

27. Tornado Safety Tips • If outdoors: • If possible, get inside a building. • If shelter is not available or there is no time to get indoors, lie in a ditch or low-lying area or crouch near a strong building. Be aware of the potential for flooding. • Use arms to protect head and neck.

28. Tornado Safety Tips • If in a car: • Never try to out drive a tornado in a car or truck. Tornadoes can change direction quickly and can lift up a car or truck and toss it through the air. • Get out of the car immediately and take shelter in a nearby building. • If there is no time to get indoors, get out of the car and lie in a ditch or low-lying area away from the vehicle. Be aware of the potential for flooding. This is why you never stay in your vehicle during a tornado.

29. Actions After a Tornado • Help injured or trapped persons. Give first aid when appropriate. • Don't try to move the seriously injured unless they are in immediate danger of further injury. • Call for help. • Turn on radio or television to get the latest emergency information. • Stay out of damaged buildings. Return home only when authorities say it is safe. • Use the telephone only for emergency calls. • Clean up spilled medicines, bleaches, or gasoline or other flammable liquids immediately. Leave the buildings if you smell gas or chemical fumes. .