Tornadoes are one of the deadliest natural hazards in the world. The cost of damages they leave behind can sometimes be monumental. Worse, they could leave in its wake hundreds of dead bodies both humans and animals.
In spite of the many studies already conducted on tornadoes, scientists have yet to find its exact meaning and classifications. The National Weather Service (NWS) defined tornado as a violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often visible as a funnel cloud (http://www.nws.noaa.gov).
The frequency and magnitude of tornado depends upon its location. In the U.S., there is a so-called Tornado Alley where tornadoes usually occur. This geographic location includes Texas and Oklahoma.
The have been two known measuring scales for tornado. One is the F-scale and the other is the TORRO scale. The F-scale was developed by Dr. T. Theodore Fujita. It measures the intensity of the tornado based on the damage it has left behind. On the other hand, the TORRO scale was invented by Terence Meaden of the TORRO group. It measures tornado intensity between T0 and T10 and relies solely on wind speed for classification. In actual practice, damage is utilized in both systems to infer intensity.
A significant percentage of the worlds tornadoes occur in the United States because of its unique geographical sketch that breeds strong, long-lived storms annually. In effect, a number of lives have already been lost. Millions-worth of properties have also been damaged.
Table of Contents
Table of Contents 3
Data Presentation 5
Discussion and Analysis 9
Tornado is one of the deadliest of the earths natural hazards. It can damage lives as well as properties. Perhaps the most popular tornado that took place happened in The Wizard of Oz, transporting Dorothy and her friends to another place. Of course, this story is just fiction; nevertheless, it depicts the damage a tornado could inflict in a place.
It is therefore essential to study tornado to mitigate its impact on the lives of millions of people. First of all, it is important to define tornado. According to the National Weather Service (NWS), a tornado is a violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often visible as a funnel cloud. However, a vortex must be in contact with the ground and the cloud base for it to be classified as a tornado. Moreover, it is also accepted that a tornado may not always have a discernible funnel.
To say that tornadoes are formed when warm moist Gulf air meets cold Canadian air and dry air from the Rockies is an understatement. Many thunderstorms that have been formed under those conditions do not produce tornadoes. In other words, not every thunderstorm spawns a tornado.
Weather scientists say that the most destructive and deadly tornadoes occur from supercells. These are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. Tornado formation is controlled mainly by the things that happen on the storm scale ” in and around the mesocyclone. Recent theories indicate that once a mesocyclone is in progress, tornado development is related to the temperature differences across the edge of downdraft air wrapping around the mesocyclone. Mathematical modeling studies of tornado formation also indicate that it can happen without such temperature configurations. In fact, very little temperature fluctuations has been observed near some of the most destructive tornadoes.
Tornadoes can appear from any direction. Some have even changed direction amid course. Tornadoes need a source of instability and a larger-scale property of rotation to keep them going (Liu 1996). There are a lot of processes around a thunderstorm which can possibly rob the area around a tornado of either instability or vorticity. For decades, storm observers have documented the death of numerous tornadoes when their mesocyclones weaken after they become wrapped in outflow air. The irony of it all is that some types of thunderstorm outflow may wipe out tornadoes, while others help to cause them.
It must also be noted that it is very hard to measure pressure in tornadoes because most weather instruments cannot survive its force (Golden 2000). However, the F-scale and the T-scale have been developed recently to help measure the intensity of tornadoes.
Dr. T. Theodore Fujita developed a damage scale called F-scale ” for winds, including tornadoes, which relates the intensity of the wind to the degree of damage that has occurred.
The original F-scale winds were arbitrarily attached to the damage scale based on 12-step mathematical interpolation between the hurricane criteria of the Beaufort wind scale, and the threshold for Mach 1 (738 mph). Though the F-scale actually peaks at F12 (Mach 1), only F1 through F5 are used in practice, with F0 attached for tornadoes of winds weaker than hurricane force. Again, F-scale wind-to-damage relationships are untested, unknown and purely hypothetical. They have never been proven and may not represent real tornadoes. Therefore, F-scale winds should not be taken literally.
Fujita plotted hypothetical winds higher than F5. However, they were only guesses. Even if a winds measured by portable Doppler radar had been over 318 mph, the tornado would still be rated only F5 since F5 is the most intense possible damage level. Even on the Enhanced F-scale, there is no such thing as F6.
Moreover, a tornado is classified as significant if it does F2 or greater damage on the Enhanced F scale. Of course, no tornado is essentially unimportant. Any tornado can kill or cause damage. In fact, some tornadoes rated less than F2 probably could do F2 or even greater damage if they hit a well-built house during peak intensity (Tobin 1997).
However, the original F-scale will no longer be used because it has been replaced by an enhanced version. Tornado wind speeds are still largely unknown; and the wind speeds on the original F-scale have never been scientifically tested and proven. Different winds may be needed to cause the same damage depending on how well-built a structure is, wind direction, wind duration, battering by flying debris, and a bunch of other factors. Even meteorologists and engineers highly experienced in damage survey techniques often came up with different F-scale ratings for the same damage. Even with all its flaws, the original F-scale was the only widely used tornado rating method for over three decades. The enhanced F-scale takes effect on February 2007 (wikipedia.org).
The Enhanced F-scale
The enhanced F-scale, on the other hand, is a much more precise and robust way to assess tornado damage than the original. It classifies F0-F5 damage as calibrated by engineers and meteorologists across 28 different types of damage indicators. The idea is that a one size fits all approach just does not work in rating tornado damage. In fact, a tornado scale needs to take into account the typical strengths and weaknesses of different types of construction. This is because the same wind does different things to different kinds of structures.
In the enhanced F-scale, there will be customized standards for assigning any given F rating to a well anchored wood-frame house compared to a garage, school, skyscraper, unanchored house, barn, factory, utility pole or other type of structure. In a real-life tornado track, these ratings can be mapped together more smoothly to make a damage analysis.
Of course, there still will be gaps on a track where there was little or no damage, but these will be less common than under the original F-scale. As with the original F-scale, the enhanced version will rate the tornado as a whole based on most intense damage within the path. There are no plans to systematically re-evaluate historical tornadoes using the Enhanced F-scale.
It must be noted that big fat tornadoes are not the strongest ones. There is a statistical trend toward wide tornadoes having higher F-scale damage. This goes to show that the size or shape of any particular tornado does not say anything conclusive about its strength.
The TORRO scale
The Tornado and Storm Research Organization (TORRO) is a research body serving international and national public interest, supported by private entities (www.torro.org.uk). Founded in 1974, most of its supporters are British.
With limited income, the nucleus of TORROs activity has been in data collection, site investigations and mainly climatological research (www.torro.org.uk). The group likewise produced the so-called TORRO tornado intensity scale, or T-Scale. Developed by Terence Meaden, it measures tornado intensity between T0 and T10. The scale was tested from 1972-1975 and was made public at a meeting of the Royal Meteorological Society in 1975 (wikipedia.org).
The TORRO scale differs from the Fujita scale because it relies solely on wind speed for classification, while the Fujita scale relies on damage for classification. However, in actual practice, both systems make use of damage to surmise intensity. The TORRO scale is primarily used in the United Kingdom, while the Fujita scale is widely used in the United States, Europe, and the rest of the world.
Every continent except Antarctica have already experienced tornado. However, a significant percentage of the worlds tornadoes occur in the United States. This is because of the unique geography of the country, which breeds strong, long-lived storms many times a year. Other areas which often experience tornadoes are south-central Canada, northwestern Europe, east-central South America, South Africa, and south-central Asia (nws.noaa.gov).
Tornadoes also occur in all regions of the United States. In fact, at least 1,000 tornadoes are accounted for annually. Some areas in the U.S. are more prone to tornadoes than others. For example, the area extending from the Dakotas south to Texas experiences the creation of many tornadoes. In fact, it has become known as Tornado Alley (intelihealth.com).
Discussions and Analysis
As has just been discussed, all 50 states of the United States of America have already been hit by tornadoes. However, this does not happen annually. In fact, in Alaska, Rhode Island and Vermont, the 30-year average number of tornadoes per year is closer to zero. In Oklahoma and Texas, the average number is 52 and 126, respectively. However, relatively the high number of tornadoes visiting Texas is credited mainly to its sheer size.
To account for the different sizes of states, tornado averages for the USA are compared by looking at the annual number per 10,000 square. For example, Oklahoma is about 70,000 square miles. If the entire state averages 52 tornadoes every year, then the number per year per 10,000 square miles is 52 divided by seven. This equals a little more than seven.
While no state is immune to tornadoes, there are places where they touch down more often. The highest concentration of tornadoes is in the area of Oklahoma and Texas, and in Florida. Recurrent thunderstorms in western Florida is a significant factor in the number of twisters occurring in its area, but these tornadoes are generally weak (usatoday.com).
. Generally speaking, the west coast of Florida has the highest occurrence of tornadoes in the USA. But this includes all tornadoes; violent, strong and weak (Manhattan 2003).
The Texas Tornadoes
One of the most remembered tornado in the U.S. is the one which occurred in Saragosa, Texas on May 22, 1987, between 8:15 p.m. and 8:20 p.m. It was a violent, multiple-vortex tornado, with winds of 207-260 mph. so it inflicted widespread damage throughout the town. Naturally, the worst damage occurred in the residential and business areas where structures were totally destroyed. Many automobiles were hurled several hundred feet into buildings and homes. One hundred three families incurred severe economic losses. Thirty people were killed and 131 injured (cdc.gov).
The Oklahoma Tornado
For the record, the May 3, 1999 Oklahoma Tornado Outbreak was the first stage of a severe weather event that lasted from May 3 to May 6. It brought violent storms to Oklahoma, Kansas, Arkansas, and Tennessee. Forty-eight people died during the outbreak. This tornado caused $1.1 billion in damage, making it the costliest single tornado in U.S. history. The Oklahoma tornado mentioned above could have delivered more blows and damages had early warnings been not made. Fortunately, early warning saved many lives. These were issued in advance of the tornados arrival. Broadcast media interrupted programming to follow the storms on radar and even by helicopter. The death toll would have been much higher if people had not been warned so far in advance (wikipedia.org).
Indeed, the damages inflicted by tornadoes can sometimes be monumental. This is the reason why everybody must always be prepared. In this sense, the adage prevention is better than cure is apt. For example, in Texas, the aftermath of the tornado resulted to contusions, lacerations, and fractures among its citizens. In addition with injuries connected to the immediate impact of the tornado, post-impact injuries were sustained by residents or emergency workers. This is the reason why residents of states often visited by tornadoes should always be alert and prepared for any eventuality. They should always have their first aid kit on hand to mitigate any injury.
Even federal governments should be able to find ways and means to alleviate the disastrous effects of tornadoes. As history will tell, there are some states in the U.S. which are frequented by tornadoes and data on this should be used to devise plans that will lessen the negative impact of natural disasters like tornado. Close coordination among government agencies should also be done. This is the only way that the effects of tornadoes can be reduced.
The study of tornado is very crucial to mitigate its after-effects. For the longest time, tornadoes have inflicted costly damage to human lives and properties in the United States of America. In spite of the several studies undertaken on this area, tornado remains one of the most complicated, yet dangerous, natural hazards. Its unpredictability makes it hard for weather scientists to prepare people for its onslaught.
Weather scientists try to estimate the intensity of a tornado by basing their judgment on its rotational speed and amount of debris being generated as well as its width, but the official estimate is always made after the tornado has passed (Mileti 1999). The development of the F-scale and the T-scale has made it possible for scientists to measure the intensity of each tornado after its occurrence.
An important point to remember is the fact that the size of a tornado does not really indicate its intensity. Large tornadoes can be weak, while small ones can be violent and deadly.
In the meantime, the best thing that people who live in tornado-prone areas can do is to be always prepared for its coming. Preparation for a tornado-visit is very crucial in mitigating the damage of this natural disaster. As history has shown, being caught off guard by tornado can be fatal and costly.
In the so-called Tornado Alley, people have learned the bitter lesson of their annual tornado encounters. Yet, despite this tornadoes can still attack viciously around the area. Although the deadly effects of tornado have already lessened through the years, they are still capable of inflicting costly damage on properties.
Sufficient warning and proper sheltering are critical factors in preventing tornado injuries and deaths. It has been recorded that tornado-related deaths have been declining because of improvements in warning systems (Gruntfest 1987).
Besides, further studies on tornado are recommended. These should include various aspects related to tornadoes, such as safety measures, safety provisions, and the development of a more accurate intensity measurement scales.
Moreover, alert systems should be put in place over tornado-prone areas. This goes without saying that federal governments should also be well-versed about tornadoes, their effects and their mitigation. This is the only way to minimize the damages that may be brought about by tornadoes.
Lastly, it is recommended that people should not take the warning about tornadoes lightly.
Books and Journals
Balluz, L. et al. 2000. Predictors for Peoples Response to a Tornado Warning: Arkansas, 1 March 1997. Disaster 24(1):71-77.
Budde, P. 2003. Catalyst Catastrophe Modeling Update: May 4th 5th 2003 Midwest Tornados. Minneapolis: Benfield Inc.
Cross, J.A. 2001. Megacities and Small Towns: Different Perspectives on Hazard Vulnerability. Environmental Hazards 3:63-80.
Golden, J.H., and C.R. Adams. 2000. The Tornado Problem: Forecast, Warning, and Response. Natural Hazards Review 1(2):107-118.
Gruntfest, E. 1987. Warning Dissemination and Response with Short Lead-Times. In Hazard Management British and International Perspectives. J. Handmer (ed.). Norwich: Geo Books, pp. 191-202.
Liu, SL et al. 1996. Assessment of a Severe Weather Warning System and Disaster Preparedness, Calhoun County, Alabama, 1994. American Journal of Public Health 86: 87-89.
Manhattan Mercury. 2003. Storms Damaged Dozens of Homes. May 13.
Mileti, D.S. 1999. Disasters by Design: A Reassessment of Natural Hazards in the United States. Washington, D.C.: Joseph Henry Press.
Odeh, D.J. Natural Hazards Vulnerability Assessment for Statewide Mitigation Planning in Rhode Island. Natural Hazards Review 3 (4):177-187.
Tierney, K.J. et al. 2001. Facing the Unexpected: Disaster Preparedness and Response in the United States. Washington, D.C.: Joseph Henry Press.
Tobin, G.A., and B.E. Montz. 1997. Natural Hazards: Explanation and Integration. New York: Guilford Press.
Tornadoes Natures Most Violent Storm 1993, National Oceanic and Atmospheric Administration and American Red Cross. Silver Spring, Maryland.
Tornado Basics 2006, Available at: http://www.intelihealth.com/IH/ihtIH/WSIHW000/9273/21340.html
The National Weather Service 2006, Available at: http://www.nws.noaa.gov/
Tornado and Storm Research Organization 2006, Available at: www.torro.org.uk
List of tables giving condensed information concerning tornadoes, geographical, financial, chronological, descriptive, etc. 2006, Available at: http://www.lib.noaa.gov/edocs/tornado/tornado3.html
The Online Tornado FAQ, Roger Edwars Storm Prediction Center 2006, Available at: http://www.spc.noaa.gov/faq/tornado/
Tornado Project Online 2006, Available at: http://www.tornadoproject.com/
FAQ: Tornado history, climatology 2006, Available at: http://www.usatoday.com/weather/resources/askjack/wfaqthis.htm
The Oklahoma Tornado Outbreak, Available at: www.enwikipedia.org