A tornado is a wind vortex that rotates in the atmosphere and is in contact with the clouds of cumulonimbus or, unusually, the clouds of cumulus and the surface of the earth. It is also possible to refer to a tornado as a cyclone. In different shapes and sizes, the features form, but often they look like a condensation funnel. With an average wind speed of 110 miles per hour, the most damaging and volatile weather patterns are tornadoes. Before dissipating, the most destructive storms can also reach wind speeds of up to 300 mph and can travel across a vast region. Tornadoes have occurred in every continent except for Antarctica. Most of them occur in a region in the United States known as Tornado Alley. Pulse-Doppler Radar is an instrument used to detect tornadoes before they can happen. Enhanced Fujita Scale and TORRO scale are used to rate the strength of a tornado. The weaker tornado does not destroy solid structures, but it damages trees while the strongest tornado can completely destroy skyscrapers and buildings.
The Stages of Development
A tornado is formed in a series of steps. The wind first changes its direction as it increases its speed as a result of an increase in altitude. The movement creates a horizontal spinning effect (a shear) that is invisible in the lower parts of the atmosphere. Secondly, the rotating air is tilted by the rising air present in the thunderstorm’s updraft from a horizontal to a vertical shape. A vast area of rotation (3-10 km) is formed, and the strongest tornadoes form here. The funnel rotates, and it touches down, and as a result, a tornado develops. Tornadoes mostly occur when water vapor is forced to condense by high winds in a low-pressure region to form a condensation funnel. A tornado can form on land (landspout), over a water body (water spout) or from a thunderstorm (gustnado).
Life-cycle
A tornado has a predictable life cycle once it has developed. The rear flank downdraft and the rotating air moves toward the ground forming a funnel. As this air reaches the ground, it picks up the surrounding dirt, and this causes damage. Once the funnel reaches the ground, a tornado is formed. In the next stage, rear flank downdraft (RFD) acts as the primary tornado source of energy. It begins by cooling down. The faster the cooling down of the RFD, the higher the energy of the tornado and the larger the distance it covers. During the last stage when the RFD cannot provide the tornado with sufficient energy, the vortex starts to weaken. The rotating air (mesocyclone) also begins to dissipate, and the tornado dies. However, the rotating air can begin at this following the dying one at this stage.
Characteristics
Tornadoes appear as narrow funnels that have little clouds of debris at the lower end. However, they may assume different shapes and sizes. The landspouts are weaker and may only appear as small swirl of dust, but the condensation funnels may fail to reach the ground. Enormous tornadoes may assume a wedge shape and are referred to as stovepipes. When dissipating, tornadoes can resemble ropes or narrow tubes. Multiple-vortex tornadoes can appear as a group of swirls that circle a common center. Weak tornadoes or strong but dissipating may be only some few miles across in size. The stovepipe tornado may have a damage path of about 1.6 km wide or even more.
Tornadoes appear in different colors depending on the area. In dry environments, tornadoes are invisible, only small debris is seen at the base of the funnel, and it assumes a gray or white color. Waterspouts appear as blue or very white. Those tornadoes that take a lot of debris from the ground appear darker while those in the high plains can turn red due to the color of the soil. Tornadoes can also assume different colors depending on lighting and sunlight.
Tornadoes usually rotate in a counter-clockwise manner when seen in the northern hemisphere and clockwise manner when seen in the southern hemisphere. They are not affected by the Coriolis Effect. During the formation of tornadoes, different sounds are produced due to multiple mechanisms. Many sounds have been reported, for instance, a sound of a jet engine, waterfall, and freight train. However, most tornadoes are not audible from a distance. These sounds depend on the nature of the atmosphere at that time as well as topography.
Types of Tornadoes
A multiple Vortex is a kind of tornado that has two or more columns that spin in the air while rotating around the same center. Landspouts appear as dust-tubes on land and have small condensation funnels which do not make it to the top most of the time. Waterspout tornadoes are similar to land spouts only that they appear over water bodies. The water sprout form at the bottom of clouds in tropical and subtropical water bodies, for instance, West Florida and the Adriatic Sea. A gustnado is also a type of tornado that forms when a fast moving cloud develops a thunderstorm and is blown through a non-moving humid air to the boundary. A supercell tornado form from a supercell thunderstorm. Dustdevils is a type of a vortex formed when the sun heats a dry area of land creating a swirling column of air. Derechos are created as a result of wind events and are not real tornadoes.
Regions
Tornado Alley is an area in the United States where tornadoes are likely to occur. It includes Texas, Kansas, Nebraska, Iowa, Minnesota, and South Dakota. About 1,200 tornadoes are formed in the U.S yearly. Tornado season refers to a time of the year tornadoes occur in the U.S. May to June is the season the Southern Plains sees most tornadoes, June-July for Northern Plains and earlier spring for the Gulf Coast. However, tornadoes can occur anytime but mostly between 4-6pm.
Measurement and Effects
Fujita scale was used to rank tornadoes, and in the year 2007, the Enhanced Fujita Scale was introduced. It ranges from EF0 (damages only trees with winds of up to 137 km/h) to EF5 (a devastating tornado that destroy buildings and trees with winds exceeding 322km/h). The strength of a tornado is measured by the damage caused. A tornado causes numerous structural damages. These losses usually happen after a tornado has left a region. Tornado winds and debris cause the losses, whereas broken wood, glasses, and nails lead to most of the physical injuries.
Precautionary Measures against Tornadoes
Having a safe room in the house with no windows is one of the precautions one can take to prepare for a tornado. The government has built houses with storm cellars, and it has saved thousands of lives in tornado-prone areas. Weather radios also play a bigger role in alerting people if there is a tornado coming. The knowledge about the different types of tornadoes also prepares people on the adverse effects of the calamity.
