Tornados Presented by Bridget Bower Sarah Weaver Kris

Tornados Presented by: Bridget Bower Sarah Weaver Kris Brownlee Allie Bogenschutz

What Causes A Tornado? 1. Warm air moves north. It collides with cold winds and dry breezes. 2. The moisture in the warm air rises and condenses into large clouds. 3. The clouds grow larger and larger. Finally, a thunderstorm is brewed up with a strong updraft. 4. The air starts to rotate. 5. The most violent tornadoes come from a super-cell thunderstorm. A super-cell thunderstorm is a massive cloud structure that has fantastic lightning and a long- lasting, strong updraft. 6. The updraft spins upwards and feeds energy into the super-cell. Within the spinning winds, a spiraling column of air is formed. This is called a vortex. However, the tornado is not yet formed. 7. Dry winds from the west swarm in and up into the super-cell clouds. It evaporates the moisture. 8. The evaporation results with the air cooling and sinking. It acts together with the updraft and makes the vortex spin faster and tighter. 9. The vortex stretches downwards and finally touches ground. This is now our tornado!

What Damage Can It Do? Ø Chimneys break. Ø Roofs are torn open. Ø Buildings are crushed. Ø Miscellaneous items are blown away. Ø Fields are covered with debris. Ø People could be killed.

How Can We Stop This? Ø Support buildings to keep them from being blown away or toppled. Ø There is no way of stopping a tornado, but you can always prepare yourself. Ø Keep a First Aid kit at handy. Ø When it hits, find a safe place to hide it out. That would be in a basement or closet. If either cannot be accessed, hide under a sturdy piece of furniture.

Why Do People Still Live There? Ø Risk perception. (people think: “It won’t happen to me!”) Ø Job Ø Family and friends. Home. Ø Too expensive to move. Ø Good land (tornado alley has lots of land that is good for growing cereals)

How Can We Predict This? Ø Sadly, there is no way we can accurately predict tornadoes. Ø But, we still can use weather balloons to measure the weather and many warning systems that can spread news of on coming tornadoes quickly.

Where Do They Occur? Ø Whenever and wherever conditions are right, tornados are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. They occur mostly during the spring and summer; the tornado season comes early in the south and later in the north because spring comes later in the year as one moves northward. They usually occur during the late afternoon and early evening. However, they have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America.

How tornadoes form? • Prior to a thunderstorm, a change in the direction of wind, and increase in wind speed with increase in height. An invisible, horizontal spinning affect is created in the lower atmosphere. BB

• Next, rising air forces the updraft to tilt the rotating air from horizontal to vertical. BB

• An air area extends 2 -6 miles throughout the storm BB

• A rotating wall is then formed. • The rotating wall is formed when the storm intensifies the updraft in low-level air from several miles away. Some of this low-level air Is pulled into the updraft from the rain area. This rain-cooled air is humid and the moisture condenses to form a wall-cloud. BB

• Lastly, a tornado is formed. BB

What are the conditions needed for a tornado to form? • Moisture in the lower to middle of the atmosphere • Unstable air, that will continue to rise. • In some cases a lifting force needs to be present to help the air to begin to rise. BB

The Fujita Scale of Tornado Intensity • The Fujita Scale is used to rate the intensity of a tornado by examining the damage caused by the tornado after it has passed over a man-made structure. • Professor Fujita and Allen Pearson, directors of the NSSFC (National Severe Storm Forecast Center) in 1971 both created the scale, also known as The Fujita – Pearson Scale. • There are 6 parts to the scale. • SW

Category F 0: Light Damage (<73 mph); Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged. Category F 1: Moderate Damage (73 -112 mph); Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off road. Category F 2: Considerable Damage (113 -157 mph); Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground. Category F 3: Severe Damage (158 - 206 mph); Roofs and some walls torn off well-constructed houses, trains overturned; most trees in forest uprooted; heavy cars lifted off ground and thrown. SW

Category F 4: Devastating Damage (207 - 260 mph); Well-constructed houses leveled; structure with weak foundations blown off some distance; cars thrown and large missiles generated. Category F 5: Incredible Damage (261 - 318 mph); Strong frame houses lifted off foundations and swept away; automobile sized missiles fly through the air in excess of 100 meters (109 yards); trees debarked; incredible phenomena will occur. Category F 6: Inconceivable Tornado (319 – 379 mph); These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F 4 and F 5 wind that would surround the F 6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F 6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies. SW

• Tornadoes Occur Anywhere • Carolinas Outbreak: • March 28, 1984, afternoon-evening 22 tornadoes 57 deaths 1, 248 injuries damage $200 million 37% of fatalities in mobile homes • Pennsylvania-Ohio Outbreak: • May 31, 1985, late afternoon-evening 41 tornadoes, including 27 in PA and OH 75 deaths in US 1, 025 injuries damage $450 million • Plains Outbreak: • April 26 -27, 1991, afternoon of 26 th through early morning 27 th 54 tornadoes 21 deaths 308 injuries damage $277+ million 15 deaths in/near mobile homes, 2 deaths in vehicles. SW

Frequency of Tornadoes can occur at any time of the year. In the southern states, peak tornado occurrence is in March through May, while peak months in the northern states are during the summer. Note, in some states, a secondary tornado maximum occurs in the fall. Tornadoes are most likely to occur between 3 and 9 p. m. but have been known to occur at all hours of the day or night. The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70 mph. The total number of tornadoes is probably higher than indicated in the western states. Sparse population reduces the number reported. SW

Office Buildings: go to an interior hallway on the lowest floor Homes: go to the basement or a place in the middle of the house, like a closet, bathroom, etc. Shopping Centers: Do NOT go to your car! If there isn't a pre-designated shelter, go to a middle hallway on the lowest floor. Schools: Stay away from auditoriums or gymnasiums with wide, huge roofs that could collapse easily Cars/Mobile Homes: leave them and find shelter in a building. If there is no shelter nearby, move away from the tornado's path. Lie flat in the nearest ditch, ravine or culvert with your hands shielding your head. -Defense Supply Center,

“…more deaths occured in a single city than from any other tornado in U. S. history. ” –tornadoproject. com Towns: Murphysboro, Gorham, De. Soto Date: March 18, 1925 Deaths: 695 Injured: 2027

Tornadoes can occur in any month but March through June is considered tornado season. Historically, the most destructive tornadoes strike in March and April. 2 nd Most Destructive: The Natchez Tornado Towns: Concordia, LA & Adams, MS Date: May 7, 1840 Deaths: 317 Injured: 109 3 rd Most Destructive: St. Louis Tornado of 1896 Towns: St. Louis, MO &Madison, IL Date: May 27, 1896 Deaths: 255 Injured: 1000

4 th Most Destructive: The Tupelo Tornado Towns: LEE / ITAWAMBA Date: April 6, 1936 Deaths: 216 Injured: 700 5 th Most Destructive: The Gainesville Tornado Towns: HALL Date: April 6, 1936 Deaths: 203 Injured: 1600

In the early morning hours of April 9, 1999, tornadoes swept through Cincinnati, killing four and causing more than $25 million in damage to homes and businesses.

• April 9, 1999 • Sycamore/Symmes Township • Four Dead

Sources http: //federalvoice. dscc. dla. mil/federalvoice/020313/Tornado. html http: //www. tornadoproject. com/toptens. htm#top http: //www. cincinnati. com/tornado/ http: //www. noaa. gov/tornados. html http: //whyfiles. news. wisc. edu/013 tornado/predict. html http: //www. fema. gov/library/tornadof. htm http: //www. indystar. com/library/factfiles/history/weather/tornadoes. html Sands, Stella. Kids Discover Tornadoes. New York: Kids Discover 1996