Tornadoes. Tornadoes are an interesting topic because as often as they occur in the United

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Jade Hunter
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1 John Bucaro Environmental Hazards Dr. Scott 9/17/03 Tornadoes Tornadoes are an interesting topic because as often as they occur in the United States scientists still do not know much about them. They occur very randomly throughout the Midwest and they don t last very long. The strongest tornadoes, which are rare, can last slightly over an hour. These two factors plus the violent nature of the storm, and their small spatial extent make them very hard to study. Many studies are still being conducted on the formation of tornadoes. Scientists are studying what they call the vortex and vortex synthesis. The vortex is a theory on how the funnel of spinning air is started. We know under what conditions tornadoes usually occur but it is yet to be determined how exactly they begin. It is not even known precisely how strong the winds of a tornado are. The scale used to measure tornadoes is a theoretical scale based on the damage. Experts estimate how strong the wind would have to be to do the damage sustained by the area in the path of the tornado. No instrument has been developed yet that can accurately detect the wind speed inside a tornado. Some people we call storm chasers have made a life out of chasing tornadoes and trying to gather and analyze data they receive. Again, the tornadoes randomness to occur and ferocious spinning nature cause the storm chasers efforts to produce marginal data.

2 tornadoes. The following topics and notes offer some of the information we do know about Definition of a tornado: - A violently rotating column of air extending down from a thunderstorm. - Narrow column of rapidly spinning air associated with frontal thunderstorms. Magnitude: - Tornadoes are measure using the Fujita scale. - The Fujita scale is a theorized scale based on estimated wind speed by analyzing the amount of damage done by a tornado. - Instruments are yet to be developed that can measure the exact wind speed of a tornado as it occurs. - In theory since we cannot precisely measure the wind speed of tornadoes there is no real end to the Fujita scale, it can be infinite SCALE STRENGTH WIND SPEED DAMAGE F0 Weak mph Light damage, broken tree limbs F1 Weak mph Moderate damage, mobile homes overturned, roofs peeled off F2 Strong mph Considerable damage, mobile homes demolished, big trees snapped, light object projectiles. F3 Strong mph Severe damage, trains overturned, cars lifted and thrown, F4 Violent mph Devastating damage, houses

3 leveled, largeobject projectiles. F5 Violent Incredible damage, incredible phenomena occur. Spatial Extent: - Tornadoes area a fairly localized hazard. - They are usually about yards wide but can be up to about a mile wide at the surface, they get wider as you approach the top of the funnel. - They can travel great distance along the ground, but usually don t. The record is 343 miles. - They can travel anywhere from 0-75 mph but typically travel mph. Frequency: - The U.S. usually experiences about tornadoes a year accounting for about 50 deaths and 1500 injuries. - It Is estimated that many more occur but go unrecorded because they occur in an unpopulated area. - The area of most frequent tornadoes is in the Midwest, an area called Tornado Alley. Seasonality: - The most common time of year for tornadoes is in the spring time. This is because the air over the Gulf of Mexico is relatively warm to the cold air coming down from Canada. When these two air masses meet in Tornado alley a lot of frontal uplifting occurs and thunderstorms which have tornado creating potential are formed.

4 - States further to the north will experience a peak season closer to summer while states further south will experience a peak season closer to late winter/ early spring. Diurnal Factors: - Tornadoes are known to occur at any time of day but typically occur between 3 and 9 PM. - The earth has received the most insolation and it s surface temperature is the greatest causing rising unstable air which can spawn tornadoes. Countdown Interval: - This is a vague topic for tornadoes. Since we cannot assess the strength til seeing the damage afterwards and we cannot precisely mark the time a tornado begins and when it peaks countdown interval is not a relevant measure for tornadoes. Spatial Distribution: - Tornadoes are a uniquely American hazard. The U.S. has a unique setup which is ideal for the creation of tornadoes throughout the Midwest. - The Rocky Mountain range to the west funnel the cold Canadian air mass towards the south where it meets the warm gulf air mass. This area is extremely flat allowing and unobstructed path for the two air masses. - When the two conflicting air masses meet frontal uplifting occurs and this creates rising unstable air which creates thunderstorms that can spawn tornadoes. Safety: Before the Storm:

5 Develop a plan for you and your family for home, work,, school and when outdoors. Have frequent drills. Know the county/parish in which you live, and keep a highway map nearby to follow storm movement from weather bulletins. Have a NOAA Weather Radio with a warning alarm tone and battery back-up to receive warnings. Listen to radio and television for information. If planning a trip outdoors, listen to the latest forecasts and take necessary action if threatening weather is possible. If a Warning is issued or if threatening weather approaches: 1 In a home or building, move to a pre-designated shelter, such as a basement. If an underground shelter is not available, move to an interior room or hallway on the lowest floor and get under a sturdy piece of furniture. Stay away from windows. Get out of automobiles. Do not try to outrun a tornado in your car; instead, leave it immediately. Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned. Waterpouts: Waterspouts are weak tornadoes that form over warm water. Waterspouts 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. 2 Recent occurrence:

6 - A tornado outbreak occurred in the plains of Oklahoma and Kansas in 1991 on April 26 th and 27 th. - The outbreak caused: 54 tornadoes 21 deaths 308 injuries $277+ million dollars in damage 15 deaths in/near mobile homes, 2 deaths in vehicles As we can see there is still a lot to be known about nature s most violent storm. We know some of the conditions in which tornadoes form but exactly how is still yet to be determined. We know that changing wind direction and wind speed with height causes an invisible column of spinning air horizontal to the surface. Then the rising air in the thunderstorm tilts this column of spinning air upright and causes a tornado. Tornadoes are extremely dangerous because of our lack of knowledge about them. We cannot predict them very accurately, they seem to occur at random. They seem to occur very suddenly and they can wipe out an area very fast. They are extremely powerful hosting the world s lowest surface pressure, millibars less than the surrounding air. They also are home to the worlds strongest winds, getting upwards of 200 mph. These factors plus our insufficient knowledge of how they form makes them an extremely dangerous hazard.

COMMUNITY EMERGENCY RESPONSE TEAM TORNADOES

COMMUNITY EMERGENCY RESPONSE TEAM TORNADOES Tornadoes are powerful, circular windstorms that may be accompanied by winds in excess of 200 miles per hour. Tornadoes typically develop during severe thunderstorms and may range in width from several