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Friday, October 4, 2019
Tornadoes in the United States Essay Example for Free
Tornadoes in the United States Essay Introduction            From the natural definition of tornado usually connotes a vortex of air that rapidly rotates and progress its contact with the ground. The rapidly circulating winds are very much capable of causing damage vast damage as a natural disaster. A tornado can move over a surface with few objects to be picked up and swirled about or you may not be able to see all the way to the surface beneath a funnel cloud because of intervening hills, trees, or buildings. Usually, the manifestations of these funnel clouds are already considered as indications of tornadoes, unless these manifestations are certain not to contact the ground[1]. The stretching that ultimately leads to tornado formation is due to the upward acceleration of the air at the base of the updraft[2]. Most manifestations of tornado illustrate extreme cyclonic force due to the effect called Corriolis, which connotes a counterclockwise movement of air in the northern hemisphere while the opposite direction of air’s movement in the south of equator. Anti-cyclonic tornadoes (clockwise-spinning in the northern hemisphere) have been observed[3]. Tornadoes most prominently manifest from the right side of air movement and the progress ahead from the storm center path as it touches the shores. In this discussion, the primary subject concerns with the occurrence and formation of tornadoes. The study tackles the principles comprising the formation of tornado in order to answer the main inquiry of the study. After which, the study analyzes the effects of tornado occurrence in the environment and the individuals in the perspective of its damaging effects. Lastly, the study covers the frequency of tornadoes in the United States and the most prominent parts in which tornadoes occur. Discussion Formation of Tornadoes            Although the process by which tornadoes form is not completely understood, scientific research has revealed that tornadoes usually form under certain types of atmospheric conditions. The technology and studies in predicting the tornadoes’ occurrences are presently utilized by weather experts to eventually obtain even a crude prediction for tornadoes occurrences. Weather forecast can at least provide crude predictions for the occurrence of tornado, but this information can go inaccurate due to the wide scale of outside factors influencing the tornado’s characteristics[4]. However, even with continuous and vast studies being made to further understand the behavior of these tornadoes, predicting the occurrence of weather even with crude indications are still impossible[5]. Some predictions even fall into inaccuracy at times wherein those areas with less frequent tornadoes are being populated more than those areas with predictions of tornado occurrence but with little or no manifestation of the phenomenon.  Tornadoes, rather than being spread uniformly, as the case for solid body rotation, most of the vorticity and the ascent within the interior of the tornado vortex tend to become concentrated within a narrow ring, just inside the radius of strongest winds. Under certain conditions, this ring of extremely high vorticity can break down into multiple vortices, whose signatures are clearly evident in the situations of aerial debris[6]. In fact, nature’s most violent storms are usually quite small and localized. They are generated, shaped and dominated by powerful winds that whirl around a small area of extremely low pressure, creating a revolving storm with the characteristic swirling, funnel-shaped clouds[7].            The easiest way to estimate the size of a tornado is by the size of the damage path. Usually, the common type of tornado’s path is from one to two miles wherein the width exceeds up to 50 yards. So far, the largest width the ever recorded accounts to one mile, while the smallest is considered 10 yards[8]. Tornado is formed and driven by a very low pressure winds present at its very core low pressure as its centre, which is often as much as 100mb lower than in the surrounding air. This scenario creates an overly steep pressure gradient that sucks in surrounding air and generates high wind speeds. The usual speed of the wind is in excess of 300 km/h are commonly present in Tornadoes. Geostrophic winds blow clockwise around tornadoes in the northern hemisphere and anticlockwise in the Southern hemisphere[9]. The widths of the tornadoes can vary during depending on the circulation of wind and other factors influencing their occurrences, because the size of the tornado can alter considerably during its lifetime. On other hand, the length of tornadoes’ path varies from the single point or the point of origin to more than 100 miles. The rotation in the tornadic supercell storm builds up gradually for a several hours, but the progression of the tornado itself usually occurs in much more speed than the usual expectation[10]. Typical tornado lifetimes are usually on the order of tens of minutes during which time move with the storm[11]. Most tornadoes have a diameter of less than a few hundred meters. A narrow rotating column of air that blows around a more or less vertical axis of low pressure and moves across the surface of the land is frequently described as a whirlwind[12]. The development of these Doppler radars provided a means for weather forecasters to at least obtain the status of characteristics, and event he chances of tornado for at least under circumstances. The National Weather Service has strategically located Doppler radars across the country which can detect air movement toward or away from the radar[13]. Detecting the progress of rotation within the tornadoes can enable the weather experts to determine and provide appropriate life-saving procedures. Most tornadoes eventually become surrounded by cooler, less buoyant downdraft air a the flanking line or rear flank gust front wraps around the mesocyclone, reminiscent of the way in which the cold air wraps around an occluding extratropical cyclone. As the mature tornado and its associated mesocyclne weaken and die, a new mesocyclone may form along the gust front, setting the stage for the formation of second tornado[14]. Somehow, studies have arrived to the most frequent time ranges when tornadoes usually occur; however, the accuracy of these time frames still vary according to other external factors, such as area, topographical location, climatic shifts, presence of storms, seasonal variations, etc. Tornadoes usually occur during late afternoon or early evening. They are most frequent during late spring or early summer[15]. A series of climatic cycles and transformations is thought to be the primary theory to support the ground basis for the formation of tornadoes. During its early phase, the initial event starts with the drying of cool air starts to meet up with the drying war air. In this sense, the air continuously overlaps with each other until humid air arises on the surface. Progressing to the next phase, the warmer air begins to settle in the lower altitudes in order to increase the temperature inversion, which comprises of warm, dry stratum above moist or humid air surface layer. Due to the continuous advection or the horizontal airflow, the atmospheric changes under the temperature inversion continue to warm and moisturize. As the sun heats the air at the ground surface, it starts to ascend and cool, which then forms a large cumulonimbus clouds[16]. With tornado’s unpredictable character, tornadoes and the system for its formation are still being critically studied. So far, the studies have revealed the usual occurrence of tornado resides in isolated incidents or in great numbers along a storm front. In extreme cases, these tornadoes can even generate more than 300 miles (483 kilometers) per hour and may travel over 200 miles; the average tornado is much weaker and lasts for 5 to 10 minutes on the ground and traveling 2 to 5 miles[17]. A whirling mass of cloud and debris beneath a roiling sky is a truly awesome and frightening sight. The twisting winds inside a tornado average between 100 and 150 miles per hour, but some storms generate winds in excess of 200 miles per hour[18]. After which, a cold front settles in within the temperature inversion and force the surface air up through it into the cool air above. In this phase, the growth of the clouds progress rapidly although substantial in form but does not extend above the tropopause. In this scenario, a jet stream is being produced, which moves air away from the top of the cloud and convection occurs beneath it, making the storm more intense[19]. After this phase, the tornado is likely now to develop most especially if the position and curves of the jet stream is in very favorable condition. In addition, for a tornado to form, these should be enough air to flow into the bottom of the storm, which usually coincide with the tailing hail. This initiates the descending of the cold air produced in the initial phase, which somehow help to stimulate convection current and energy transfers. Finally, tailing hail and descending cold air initiate the production and initiation of convection of currents and energy transfers. Static electricity is now produced, which consequently aids on the development of the vortex present in the tornado’s body[20]. Effects of Tornadoes on Environment and People            People and properties are usually threatened by the massive entrance of high wind speeds around the tornado, which tornadoes move across the ground. Many tornadoes move at speeds of between 150 and nearly 500 km causing massive damage in the area that it passes by. Fast-progressing tornadoes cannot be outrun, and people caught in their path are generally advised to shelter or drive away at right angles to the narrow tornado track[21]. The intensity and duration of tornadoes greatly affect the rate of damage done by this disaster to the path it passes by and the environment to which it occurred. They have vast destructive impacts on the land in which they touch whether it is city, town, country, ocean or forest. The effects of tornadoes on forests are similar to that of hurricanes wherein the strong downward circulating motions of the wind alter the composition of forest stands[22]. In emphasizing tornadoes effects in financial losses of the community, approximately $5 million a year (compared with $200 million for urban drought) is spent to provide and improve warning systems and to construct tornado shelters or storm cellars[23]. The government is ready to spend this amount of funds for the preventive preparations in order to further warn their citizens of the coming natural phenomena. This is one of the primary reasons why the number of tornado-related deaths in these tornado-prone areas tends to be lower than those with lesser risked areas. Warning time under the best conditions is not more than one hour ahead of the event. Tornadoes cause great damage they often cause total destruction where the touch the ground, because of the extremely strong winds and the powerful uplift is within them. They often follow quite well-defined paths along the ground, and this is evident in the trail of damage they leave behind including swathes cut through forest and narrow strips of buildings destroyed in residential areas[24]. On the other hand, although deaths from tornado have been reduced in recent years, the number is still relatively high, averaging about 120 a year. Economic damage from tornadoes averages about $125 million a year, as opposed to only $15 million for drought[25]. The tornadoes have been one of the most destructive events in decades, killing forty-seven people, destroying 2,000 homes and causing about US $500 million worth of damage[26]. On the other hand, from one of the most prominent site of Tornado, Kansas, several tornados were estimated to have caused $2.5-5 million in property damage. Four deaths were caused by 484 tornadoes over the 52 year period (from 1950-2002) only for this area. In terms of tornadoes’ damaging potential, a primary tornadic direct hit on one of the larger communities can cause much greater loss of life and property than in small country[27]. Areas of the U.S Being Hit the Most            Tornadoes are the most violent and destructive disasters of the Earth’s atmosphere. About 200 tornadoes a year are recorded across the United States. They are even considered as the primary climatic hazards in central and eastern areas, and particularly in the valley of the Mississippi, which is most prominently known as the tornado alley[28]. In fact, during the years from 1920 to 1950, every country in Mississippi valley and those adjoining coastal plains of the Gulf of Mexico was struck by at least a dozen tornadoes that cause extreme property damages and the crude death rate of 2000 people[29]. Although tornadoes occur in many areas of the world, the United States has more tornadoes than any other country, with an estimated 30% to 50% of the world’s total. Canada ranks as the second place in the occurrence of tornado with approximately 100 to 200 tornadoes per year[30]. In additional, tornadoes occurring in these areas tend to be more aggressive and deadly than those in other countries. Such scenario is because of the clashing of air masses east of the Rockies. The most obvious tornado alley extends from the plains of northwest Texas eastward into north Texas and then northward across Oklahoma, Kansas, and eastern Nebraska. A second tornado alley, called Midwest Alley, is located over most of Illinois and Indiana. Finally, Dixie Alley[31] stretches eastward from Arkansas, Louisiana, and Texas through Mississippi, Alabama, and Georgia. Dixie Alley also extends southward into Florida[32]. A portable Doppler radar measured a wind speed of 318 miles per hour in a tornado that struck Oklahoma City[33] on May 3, I999.[34] In this incident of tornado, the immense manifestation of tornado was not predicted accurately by the weather forecast during that point or at least, the news of its intensive manifestation arrived late, which caused the immense damage[35]. During April 26, 1991, one of the most prominent tornado occurrences in Oklahoma occurred near Red Rock. The wind measuring for 286 miles per hour was incorporated within the storm that devastated parts of Red Rock Oklahoma. In an average year, more than a thousand tornadoes are likely to touch down across the United States[36]. However, it is fortunate for the community that weather analysts can provide advance warning for the coming or at least a crude prediction of tornado occurrence in their area. In this way, the public is able to prepare for the coming of tornadoes; hence, reducing the damage this phenomenon can cause. Knowing that these Tornadoes happen predominantly during the afternoon and early evening, the exact ranges of time frames based on previous historical occurrence of tornadoes state 2:00P.M. until 7:00 P.M local time. On the other hand, the time wherein tornadoes usually show immense activity is from 5:00 P.M. to 6:00 P.M. Such time frame is very much evident in smaller alley or regions such as the Dixie Alley[37]. A broad swath from central Texas to eastern Nebraska comprises the heart of ‘tornado alley,†which extends southward through the Gulf States and eastward to the Ohio Valley. No other place in the world experiences more tornadoes than the nation’s heartland, although twisters are not confined to the Midwest and southern states[38]. In addition, the national tornado season is clearly from April through July; however, tornado season in the United States never really begins or ends but is ongoing[39]. Most tornadoes tend to build up inside very large storms, and these are usually found in unstable environments in which wind speeds vary with height and where cool, dry air rests on top of warm, moist air, with a thin, stable layer separating the two air masses[40], a condition similar to temperature inversion in other settings[41].            In the United States, those areas with high occurrences of tornadoes have relatively low rates of tornado-related deaths, partly because of variations in population density, but the provided proofs show a variation over time in the location of tornadoes, which is placing significant numbers of less well-prepared individuals and communities at risk. Death rates from tornado-related injuries in the United States are the highest among people living in mobile homes, the elderly (over 60 years of age) and people caught outside with no protection when the tornado passes by[42]. One of the most historical events that occurred in Pennsylvania was during 1998 wherein fifty-nine tornadoes, plus several waterspouts over the open waters of Lake Erie were counted for just one season. According to climatologist and weather analysts, the most damaging tornadoes that occurred within this area of Pennsylvania from 1865, 1896, 1944 and 1998 are only products of stronger western and southern storms that usually struck in late spring[43]. Conclusion            As for the conclusion of the subject, tornadoes in the United States have indeed manifested in greatest terms wherein U.S has been considered as the top most destination for the occurrence of tornadoes. From the discussion of tornadoes, formation, it has been uncovered that the origin of these phenomenon are from the contacts of war and cold air that contradicts to form humid, moisture and temperature variance, which in the end, initiate static electricity that causes the formation of the vortex. From the discussion on the effects of tornadoes, it has been uncovered the main destruction caused by this event is on the property and physical aspect wherein significant economic cost decline are mainly affected especially for those occurring in larger communities. Lastly, the areas where tornadoes mostly occur are Nebraska, Oklahoma, Kansas, Texas, and those areas within the tornado alley or Mississippi. Bibliography Alexander, D. E. (2003). Natural Disasters. Springer. Barnes, P. L. (1999). The Oryx Guide to Natural History: The Earth and All Its Inhabitants. Greenwood Publishing Group. Burton et.al., I. (1993). The Environment as Hazard. Guilford Press. Essex, S. (2005). Rural Change and Sustainability: Agriculture, the Environment and Communities. CABI Publishing. Gelber, B. (2002). The Pennsylvania Weather Book. Rutgers University Press. Gunn, A. (2001). The Impact of Geology on the United States. Greenwood Publishing. Hagget, P. (2002). Encyclopedia of World Geography. Marshall Cavendish. Konvicka , T. (1999). Teachers Weather Sourcebook. Libraries Unlimited. Pack, C. C. (2001). The Environment: Principles and Applications. Routledge. Tawrell, P. (2006). Camping Wilderness Survival: The Ultimate Outdoors Book. Paul Tawrell. Wallace, J. M., Hobbs, P. B. (2006). Atmospheric Science: An Introductory Survey. Academic Press. [1] Tawrell, P. (2006). Camping Wilderness Survival: The Ultimate Outdoors Book. Paul Tawrell. p.674 [2] In a typical supercell storm the rate of ascent w increases from near zero at the ground to ~3 m s-1. Hence, the e-folding time T for the amplification of the vorticity is 300s (Wallace, J. M., Hobbs, P. B. (2006). Atmospheric Science: An Introductory Survey. Academic Press. P.360). [3] Tawrell, p.674 [4] Tawrell, p.674 [5] Tornadoes usually form when warm, humid air is sucked into a low-pressure cell. There it arrives into contact with a cold front accelerating towards it from the counter directions. The steep temperature gradient permits the tornado to facilitate along the squall line either in front of or along the cold front. In the United States, tornadoes are most common in the Mildwest and along the east coast (Park, C. C. (2001). The Environment: Principles and Applications. Routledge. P.315) [6] Wallace, Hobbs, p.360 [7] Powerful updraughts within increasing column of air provide the tornado its strong vertical progression, and the circulating form is induced by strong winds that are drawn into the low pressure center (Park, p.315). [8] Tawrell, p.674 [9] Park, p.315 [10] Wallace, Hobbs, p.360 [11] On the other hand, non-supercell tornadoes form when a patch of boundary layer air with circulation about a vertical axis comes into vertical alignment with a vigorous convective-scale updraft. The source of the vorticity may be a gust front, a convergence line, or wind shear induced by flow around a topographical feature (Ibid, p.361) [12] Tornadoes form over dry land, but when the funnel-shaped vortex comes into contact with a lake or sea it sucks up particles of water and whirls them around in a spiral pattern as a waterspout (Park, p.315). [13] Tawrell, p.674 [14] Wallace, Hobbs, p.360 [15] Park, p.315 [16] Alexander, D. E. (2003). Natural Disasters. Springer. P.172 [17] The United States is the most tornado-prone country in the world, with the main characteristic of tornadoes that range from average to extreme. The usual area of occurrence relies in Great Plains or the Tornado Alleys (Barnes, P. L. (1999). The Oryx Guide to Natural History: The Earth and All Its Inhabitants. Greenwood Publishing Group. P.55) [18] Gelber, B. (2002). The Pennsylvania Weather Book. Rutgers University Press. P.135 [19] Alexander, p.172 [20] Ibid, p.172 [21] Park, p.316 [22] Tornadoes, by contrast, are intensive hazards that threaten about +0 million people living in the areas of higher tornado incidence in the Midwest, the Great Plains, and the Gulf States. Tornadoes are comparatively rare events with high energy outputs and arc highly localized, with a very rapid onset. Moreover, although between six and seven hundred tornadoes occur every year, the average path is quite small. There is little incentive, therefore, to invest in protective measures, since their likelihood of being needed in any one place is small and, given the force of a tornado, such measures are often not effective (Baumann and Sims, 1972; cited from Burton et.al., I. (1993). The Environment as Hazard. Guilford Press. p.42). [23] Burton et.al. p.42 [24] Park, p.317 [25] Burton et.al. p.42 [26] Park, p.316 [27] Essex, S. (2005). Rural Change and Sustainability: Agriculture, the Environment and Communities. CABI Publishing. P.175 [28] America’s known â€Å"Tornado Alley†or the Mississippi is the area with the most prominent occurrence of twister that entails great damage and destruction; however, few periods see as much activity as on one night in mid May 1999, when seventy-six twisters ripped through Oklahoma, Nebraska, Kansas and Texas (Park, p.316) [29] Hagget, P. (2002). Encyclopedia of World Geography. Marshall Cavendish. P.84 [30] Konvicka , T. (1999). Teachers Weather Sourcebook. Libraries Unlimited. P.200 [31] Tornado incidence increases in Dixie Alley in February. During the spring, tornadoes become more common farther west and north, extending into Texas and the Tennessee Valley. By May and June, tornado frequency increases in the plains of Texas, Oklahoma, Kansas, and Nebraska. In July, tornado frequency shifts 10 the Dakotas, the Upper Midwest, and the Great Lakes region while decreasing to a minimum in Dixie Alley. An interesting secondary peak is evident in November, particularly in Dixie Alley (Konvicka, p.200-201). [32] Konvicka, p.200 [33] Ibid, p.200 [34] On the evening of 3 May 1999 the worst tornado of the century, as far as costs are concerned, touched down on Oklahoma City. It was the nation’s first billion-dollar one. It was not alone. Other parts of Oklahoma. the state that gets more tornadoes per square kilometer than anywhere else on earth, were hit with 65 of these storms on that same evening, all of them in areas close to Oklahoma City. Within a period of five hours 8,000 buildings were in partial or total ruin as the rash of storms swept from southwest Oklahoma diagonally across the state toward Wichita, Kansas (Gunn, A. (2001). The Impact of Geology on the United States. Greenwood Publishing.p.205) [35] The difficulties involved in forecasting were evident on that fateful evening in May. The Storm Prediction Center (SPC), based at Norman. Oklahoma, issues bulletins every day, and on that morning’s statement announced it as unlikely that any tornado would appear during the day. By early afternoon SPC raised its estimate to moderate. Not until close to 4:00 in the afternoon did SPC change its prediction to high riskâ€â€and then only because a powerful computer had shown that storms were charging across the state (Ibid, 205-206). [36] Gelber, p.135 [37] Konvicka, p.200 [38] Gelber, p.135 [39] Konvicka, p.200 [40] If a weather system reaches this unstable mass, the status quo is disrupted: The low-level air is forced upward, and a vertical vortex gradually takes shape as the warm air ascends, cools to the point of condensation, and then is triggered into faster ascent as the latest heat of condensation warms the surroundings (Gunn, p.206). [41] Ibid, p.206 [42] Pennsylvania experiences an average number of eleven tornadoes annually, based on the statistical period of 1954 through 1999. However, during a ten-year period from 1989 to 1998, the average number of Pennsylvania tornadoes doubled to twenty-two . (Gelber, p.135) [43] Ibid, p.135
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