Tornado is a violent storm characterized by whirling winds extending from the surface of the earth to the base of a thunderstorm. It is in form of a column of air which is funnel shaped with the top opening up in the cumulonimbus (or cumulus) cloud and the base narrowing down to the earth surface. Although tornadoes are not visible, the funnel cloud formed can be visible due to the debris which can be seen spiraling up as a result of the strong whirling winds, (Carlyn, 2001).
According to Malder (2005) tornadoes are formed by instability in the atmosphere caused be differences in the temperature of the air. When there is a lot of heat on the surface of the earth which causes an increase in the temperature of air above it. The warm air rises owing to the decrease in its density. As the warm air reaches the surface of cold air, it exerts pressure upwards towards the cold surface of the air. As the pressure builds, the warm air breaks through into the cold air forming a thunder cloud. The warm air starts to condense once in contact with the cold air surface. Because of the continuous condensation of air coupled with the continuous flow of warm air, a stream of warm air from the ground rises up into the cloud forming a condensation funnel which descends down to the ground. The speed of air moving up may increases and the wind blowing horizontally from the opposite directions causes the upward moving air to spin up.
Place of formation
The formation of a tornado takes place in a number of steps, the first being the formation of warm humid air on above the surface of the earth, then the stage where the warm air rise up exerting pressure upon the surface of cool air above, formation of thunder cloud and the condensation funnel and finally the decay stage. At the decay stage, the condensation funnel reduces in size and becomes very thin due to the reduced supply of warm humid air since the horizontal blowing air consist of cool air. This eventually cuts off the funnel and the tornado stops, (Malder, 2005).
Time of a tornado
According to Malder (2005), the tornado can last for a short period of time or for a long period of time depending on the strength and sometimes stops due to the effect of a strong storm when it rains spreading the cold air throughout the atmosphere. The strength of a tornado is measured using the Fujita-Pearson Tornado Scale. The scale ranges from F0 to F6 where F6 is rated the strongest category of tornado, which is characterized by wind speed of about 319-379 mph. Tornadoes of this magnitude are known to cause massive destruction of property, (Newder, 2002). A tornado of F5 is the highest that can be experienced with a wind speed of 261-318 mph. This can cause immense destruction; collapse of strong houses, throwing cars away up to a distance of about 100 meter and even destroying steel reinforced structures, (Newder, 2002).
The size of a tornado varies depending on the amount of vortex wind involved. The wide varies from a few meters to hundreds of meters wide and may travel several miles from the starting point. The maximum size that can be attained by a tornado depends on the degree of temperature disturbance prevailing in the atmosphere at the time of its development, (Pastner, 1999).
On average, the size of a tornado is about 150 meters wide and extends on the ground for about 8 km. The size of a tornado varies from extremely narrow; about 2 m wide and may extend about 4 km on the ground. Such a narrow tornado is known to last a very short time. However, it is worth noting that the size of a tornado has nothing to do with its intensity. In some cases, a tornado can be small in size but may be very strong. Such a tornado may cause more destruction than other tornadoes which may be twice as large, (Carlyn, 2001).
Shape of tornado
A tornado is formed when the condensation funnel extends from the thunder cloud above to the surface of the earth. The shape of the tornado therefore is undoubtedly round. The horizontally blowing wind causes the vertically moving air to rotate and increases the speed of moving air and hence the strength of the tornado. As the warm air rise up, it cause object to spiral up and this may cause immense destruction.
The difference of tornado in northen and southern hemisphere
Tornadoes often spin in the anticlockwise direction on the northern hemisphere and in the clockwise direction in the southern hemisphere. This is due to the effect of coriolis force that is experience differently in the two hemispheres. Coriolis effect is the deflection of moving object in the opposite direction in reference to a rotating frame. The earth is a rotating frame and the tornado is spinning in the opposite direction relative to it. In the northern hemisphere, because of coriolis effect, objects spinning above the surface of the earth spin in the anticlockwise direction. That explains why, in the northern hemisphere, tornadoes spin in the anticlockwise direction. While in the southern hemisphere, they spin in the opposite direction; in the clockwise direction.
The intensities of tornadoes can be classified according to the wind speed, the time they are on the ground and the intensity of the destruction caused. According to the magnitude given by the Fujita-pearson scale (F0-F6), the intensity of a tornado increases as the wind speed increases. In this case, tornadoes are classified according to the wind speed and the impact in terms of the amount of destruction caused, (Newder, 2002).
Following Fujita scale, tornado intensities are classified as follows: an intensity of F0 with wind speed of 40-72 mph is rated as the lowest and may cause minor destruction to chimneys, branches of trees and street signs. F1 is rated as a moderate tornado with a wind speed of 73-112 mph which is the beginning of hurricane wind speed: characterized by destruction of roofs, homes and garages. F2 is classified as significant tornado with a wind speed of 113-157 mph and causes substantial destruction of property. F3 is rated as severe tornado with a wind speed of 158-206 mph and causes more adverse destruction such as uprooting trees and destruction of non-permanent buildings. A tornado which is rated F4 according to Fujita scale is considered a devastating tornado and is characterized with wind speed of 207-260 mph and destroys strong buildings and airlifts vehicles of all sizes. A tornado rating F5 is an incredible tornado with a wind speed of 261-318 mph and causes massive destruction of property; throwing away vehicles of all sizes and uproots off foundations of strong buildings. The highest intensity tornado that measures F6 on the Fujita scale is an inconceivable tornado with a wind speed of 319-375 mph. The occurrence of winds of this magnitude is however highly unlikely, this high intensity tornado may never be achieved, (Newder, 2002).
First, the massive destruction caused by a tornado is quite hazardous to the environment. Both material property and the biotic environment (both trees and animals) is affected by the fast moving wind. The biotic interdependence between the living organisms is greatly hampered and this causes a lot of instability within the environment, (Pastner, 1999).
Secondly, tornadoes cause environmental pollution. The moving air flies debris up into the atmosphere posing serous health hazard to both human being and entire living organisms. The dust fills the atmosphere and makes it unfavorable for survival of living organisms, (Pastner, 1999).
The likelihood of tornadoes occurring in different places differs depending on the climatic conditions. Netherlands has recorded the higher number of tornadoes per year, followed by UK. In the United States, an average of 1200 tornadoes is reported every year. However, most of them are small and may not cause any significant destruction. India and Bangladesh experiences a considerable number of tornadoes annually, however most occurrences are not publicized hence go unnoticed. In addition to that some countries that experience tornadoes include Argentina, Brazil, Australia New Zealand and South Africa, (Pastner, 1999).
Tornadoes are usually formed whenever the conditions are favorable. This means that they can be formed during any time of the month. They are most likely to be formed during the transitional period between autumn and spring since there are more chances of cool air meeting with warm air.
In the ancient times, tornadoes could only be detected by someone seeing it on the ground. Before a tornado, violent winds blowing and low moving clouds can be a sign of impending tornado. Tornadoes often form after thunderstorm updraft. Small clouds are formed and they quickly rise into large clouds which may lead to tornado formation. So the occurrence of a thunderstorm can be a good sign of occurrence of a tornado, (Helmen et al, 2007).
Fortunately, nowadays, weather radars are used to detect thunderstorms likely producing tornadoes. The radars have the ability to detect echoes of thunderstorms and relay radar signatures of tornadoes that are miles away. Most countries have developed a network of tornado detecting stations to enable monitor their occurrence. These stations are well coordinated to provide up to date information and warning in case of an imminent tornado. In addition, Additionally, Geostationary Operational Environmental Satellites (GOES) are to detect the presence of tornadoes in most populated areas of the earth, (Helmen et al, 2007).
Enough safety measures have to be taken both before the emergence of storm and after. The general public has to be sensitized enough about tornado safety. It is important to have an emergency safety plan for the family and the entire community. At school, it is important to teach all students on important safety techniques. Motorists also should be informed on the safety measures to employ before and during the storm. People should always listen to the radio and television in order to catch the latest on weather updates. Whenever you have your activities outdoors, ensure that you have enough information on the latest weather forecast and the necessary precautions to be taken in case of tornado occurrence, (Carlyn, 2001).
How to behave during a tornado
If a tornado warning is issued, move to previously designated safer areas such as basement of a building. If there is no building nearby, lie flat on the ground preferably a depression. When you are in a vehicle, you are not supposed to drive, instead move to a safer place. Do not try to run against a tornado since this is even more dangerous. In case of a tornado alert, do not run to inform your family members; instead make a phone call (Helmen et al, 2007).
Tornadoes are formed by disturbance in the atmosphere that is caused by the presence of warm air from the heated ground and cooler air above it. Their intensity can be measure using Fujita scale (F0-F6) with the lowest intensity tornado measuring F0 on the scale and the highest being F6. Basing on this scale, tornadoes can be classified into seven categories. These categories have different wind speed and magnitude of destruction caused. The likelihood of occurrence of tornadoes can be detected using weather radars located in the weather stations. This makes it possible to take precautionary measure against it and to avoid destruction and even loss of life.