Tornadoes-Green

Tornadoes  Eunice L. & Katherine L.   Green Class

Introduction
A tornado is a violent, narrow, counter-clockwise rotating column of air called a "vortex" that extends from a cumulonimbus thunderstorm all the way to the ground. (1) It is the smallest of all types of cyclones but has the strongest windspeed and may form anywhere at any time. However, it mostly occurs in Tornado Ally in the Midwestern United States during spring and early summer (April~June). (1,9) It has a counter-clockwise rotating condensation funnel that contains water droplets, but sometimes, tornadoes do not have a funnel and are known as a single vortex. (1,9) This severe form of weather occurs when warm and cold air meet and create an updraft of unstable air (2), which fuels a thunderstorm that is usually formed by hot and humid air in a strong updraft with a cold front. (9) A tornado generally occurs near the edge of a thunderstorm, and often sunny skies can be seen beyond it. (2) Its winds can reach up to 300 mph and its damage paths may be 1 mile wide by 50 miles long. (2) In addition, tornadoes generally move from the southwest to the northeast, although they can travel in any direction. (2) They can be visible if dust and debris (accumulation of loose fragments of rock.) are in the column of air; if not, they may be invisible. (1)

There are two different types of tornadoes that are determined by their formation. (1) One of the tornado types is formed from supercell thunderstorms, which form the most common and dangerous form of tornado because of the strong rotation of its updraft. (1) It is long-lasting (more than one hour) and occurs with a rising of warm, moist, unstable air known as an "updraft" that tilts and rotates in an area within the thunderstorm called a Mesocyclone. The other type of tornado comes from non-supercell thunderstorms with little rotation of its updraft that is not associated with a Mesocyclone. In addition, tornadoes can form over water. (1) These types of tornadoes are known as "waterspouts". (5) To learn more, visit the National Weather Service page on waterspouts.Also, to see a video clip of a tornado called the "elephant trunk tornado" visit this link. [|"Elephant Trunk" tornado]. (7)

Dangers Tornadoes can be massive, deadly storms that may strike quickly with little to no warning. (2) They may also appear transparent until they pick up debris, and they move fairly quickly at an average groundspeed of 30 mph although they can move anywhere from 0-70 mph; thus, tornadoes can be invisible and fast-approaching storms. (2) In addition, although the storms themselves may be dangerous, 50% or injuries result from the aftermath of the storm due to the vast number of nails and weak structures caused by the storms. (2) The damage that comes from the strong winds that tornadoes contain are sometimes as fast as 300 mph. (2) They cause automobiles to become airborne, rip homes to shreds, and break glasses. (3) A tornado also threatens living creatures due to flying debris. (3) People used to believe that tornadoes made buildings "explode"; however, this is not true. (3) Weak tornadoes are 74% of all tornadoes. (3) Weak tornadoes break branches and damage roofs, windows, and structures due to their winds and flying debris. (3) Strong tornadoes destroy some buildings, including a loss of outer walls or roofs, although the interior walls will most likely survive. (3) Violent tornadoes make up 67% of total tornado deaths. (3) They cause incredible damage. (3) They can lift and even throw heavy cars. (3) Strong frame houses can be leveled off and trees may be uprooted. (3) Tornadoes can result in huge monetary losses for the economy. (3) They hurt the communities hit by them through loss or injury of family members, loss of business, and the cost of emergency personnel and shelter operation. (3) A tornado also damages crops and human properties, although it remains an intangible long-lasting cost as well. (3)

Conditions of Formation Tornadoes are created when warm, humid, unstable air is lifted above cold air, sometimes by processes such as orographic lifting, convergence, frontal wedging, or localized convective lifting. They also can be created when moisture is added to the air and replaces air molecules with less dense water vapor that lowers air's density, causing it to become unstable and rise. Tornadoes often form along cold fronts due to the rising of warm air over cool air. This warm air, known as an "updraft", is wedged upward by the colder air, and it expands because as altitude increases, air pressure decreases and allows the same number of air molecules to occupy a larger volume. As air expands, it cools because there is less molecular movement per unit area. As the air keeps rising, its temperature decreases, which also decreases its capacity and increases its relative humidity. Once the air reaches its dew point (100% relative humidity), the air is saturated and condensation occurs. This condensation forms cumulonimbus clouds, which are clouds of vertical movement that are responsible for creating thunderstorms.

Tornadoes are caused by the rotation of an updraft due to wind shear (2 different levels of wind above the ground blowing at different speeds and directions). (1) Ground level winds are slower because of friction (the roughness of the ground), which deflects the wind to flow at a greater angle to the isobar, minimizing the effect of the Coriolis Effect (air flows to the right - in the N. Hemisphere - as it travels from high to low pressure). However, in the same position above the Earth's surface, wind speeds are faster due to little friction. The stronger wind at a higher altitude causes an transparent tube of air to spin horizontally. (1,5,9) The updraft from the surface tilts the spinning air so that it rotates vertically rather than horizontally. (1,5,9) This vertical cylinder of rotating air is called a "Mesocyclone" (link: a rapidly rotating air mass within a thunderstorm that often gives rise to a tornado). After a Mesocyclone forms, a tornado can develop from this area of rotation. (5) However, Mesocyclones do not always create tornadoes. (1)

The rising air in the updraft of a thunderstorm creates counter-clockwise rotating cyclones (in the Northern Hemisphere) within these Mesocyclones, which have a center of low pressure. (5) Tornadoes have such large pressure gradients that the pressure within the tornado can be 10% lower than outside of the storm. The strong center of low pressure causes the air near the ground to rush in to its center and spin inward counter-clockwise (usually). This is due to the Coriolis Effect, the tendency of free-moving objects or fluids such as wind to veer to the right of their paths in the Northern Hemisphere and to the left in the Southern Hemisphere due to Earth's rotation.

In addition, tornadoes may form from two different types of thunderstorms: one is a supercell thunderstorm and the other is a non-supercell thunderstorm. (1) Supercell thunderstorms are created by long-living (longer than one hour) updrafts that tilt and rotate. (1) The storm's Mesocyclone can be large, up to 50,000 feet tall anywhere from 20-60 minutes before a tornado forms. (1) The non-supercell thunderstorm does not have a rotation of updraft and is not associated with Mesocyclones. It is caused by wind shear from warm, cold/ sea breeze front as an updraft moves over and spins, stretches, and creates a tornado. (1) There are two types of non-supercell thunderstorms. (1) One is called a Gustrado, which is dust/debris near the ground that does not form a condensation funnel with water vapor along a gust front. (1) The other type of non-supercell thunderstorm is a "landspout" which is narrow and rope-like with a condensation funnel develop of thunderstorm clouds. (1) It is similar to a Gustrado but it occurs over water. (1)

1.) The faster wind above surface causes a horizontal spinning of air 2.) The updraft from the ground creates a "Mesocyclone" 3.) The cumulonimbus cloud creates a thunderstorm, and a tornado forms!

 Historical Examples The deadliest single tornado recorded in history was the Tri-State tornado of 1925, which occurred at 1:00 p.m. on March 18. (4) It began in northeastern Missouri, crossed the Missouri River, and tore through southern Illinois and Indiana. (4) A total of 690 people were killed and over 2,000 injured during the three-plus hours the storm spent on the ground and during its aftermath, and it cost the U.S. a grand total of $18,000,000 in 1925 dollars. (4) Illinois was hit the worst, with 540 deaths. Murphysboro, IL was smashed and 234 people were killed there alone, making it the largest death toll in a single town due to a tornado in U.S. history. (4) In West Frankfort, a small mining town, over 127 citizens died, most of them women or children. (4) Most of the men were in the mines during the time of the storm and did not realize tht anything was amiss until their power shut off. (4) They emerged from the mine only to find the destruction that the storm had left in its wake. (4) In total, the storm's ground speed averaged about 62 mph, although it may have surpassed 70 mph during its journey. (4) It traveled 219 miles, the longest distance traveled on the ground of any single tornado, was approximately .25-.75 of a mile wide, and was discovered to have been an F5 on the Fujita Tornado Intensity Scale. (4)

Another historical tornado record was the Carolina Outbreak on March 28, 1984. (5) There was a total of 22 tornadoes from the afternoon to evening. (5) 57 people died and 1,248 were injured. (5) There was $200 million dollars of damage on houses and public facilities. (5) 37% of fatalities occured in mobile homes. (5) The Pennsylvania-Ohio outbreak was even more devastating. (5) It happened on May 31, 1985 from afternoon to evening. (5) There were 41 tornadoes. (5) It caused 75 death and 1,025 injuries. (5) It cost total of $450 million dollars. (5) Also, the Plain outbreak on April 26 to 27 in 1991 had 54 tornadoes. (5) 21 people died and 308 people were injured. (5) The total cost was $277 dollars with an additional million dollars. (5)

Safety The first step to preparing for a tornado is to create an emergency kit and a family communications plan. (2) It is important to listen to warnings on the news and from officials, as tornadoes can occur with little to no warning. (2) Some warning signs of an incoming tornado are: a dark, often green-tinted sky, large hail, a loud roaring sound, dark low clouds (especially if they are rotating), and a lack of wind or air movement. (2) If you are in a structure as a tornado strikes, the safest place to be is in a safe room or the lowest level of the structure, preferably a basement. (2) Go to an interior room away from corners, doors, windows, or outside walls, and protect your head under a sturdy table. (2) It is vital not to open windows during the storm. (2) If you are in a vehicle such as a car or trailer, you should get out of the vehicle and go to the lowest level of a nearby structure. (2) If you are outside and shelter is unavailable, lie flat in a ditch or depression rather than under a bridge or other structure, and protect your head until the storm passes. (2) Never try to outrun a storm and be aware of flying debris. (2) After the storm passes, pay attention to the placement of electrical lines to avoid fires, listen for more information from authorities, and be careful of weak structures. (2) In order to avoid injury from the storm's aftermath, wear long sleeves, sturdy shoes, and gloves. (2) Finally, there may be people trapped by debris or injured during the storm; however, you should not attempt to help them alone if it endangers you as well (2). For more information, visit American Red Cross Tornado Preparation.

Sources (1) "Questions and Answers about tornadoes : Basics" //NOAA. NOAA, n.d. Web 9.Jan. 2012// 

(2) "Tornadoes." //Ready//. FEMA, n.d. Web. 9 Jan. 2012. <[]>

(3) "Question and Answer about Tornadoes:Dangers and Impact" //NOAA. NOAA, n.d. 12 Jan. 2012//
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//(4) "1925 Tri-state tornado was worst in U.S. history."// USA Today//. USA Today, n.d. Web. 10 Jan. 2012.// //.//

// (5)"Tornadoes.....Nature's Most Violent Storms" Jan.10.2012 // // [] //

// (6) Williams, Jack.// The Weather Book//. New York : Vintage Books, 1997. 124-129. Print.//

//(7)// "Storm Chaser- A Tornado Beauty", //The discovery network. n.d. Web1 2 Jan.2012// 

//(9) Edward J.Tarbuck and Frederick K. Lutgens, Prentice Hall Earth Science ;//Pearson Education, Boston, Massachusetts 02116, 2009. p.573-574. //Print//