A tornado is a violent rotating column of air which is often highly dangerous and destructive. This twisting column of air is in contact with the earth and a cumulonimbus cloud.
The word ‘tornado’ is derived from Spanish and Latin roots and means "thunderstorm". A tornado is sometimes called a "twister" or the general term “cyclone”. It is a violent rotating column of air which is often highly dangerous and destructive. This twisting column of air is in contact with the earth and a cumulonimbus cloud. Often it appears in the form of a visible condensation funnel carrying a cloud of debris and dust. The narrow end of the tornado is in contact with the surface of the earth. Tornados move around a distance of several kilometers before dissipating. They have wind speeds up to 175 km per hour and are about 75 m across. In rare cases tornados have wind speeds of more than 475 km per hour and they may be 3 km across and can move on earth for more than a hundred kilometers.
Tornados may Appear in Many Forms
There are various types of tornadoes. Waterspout, landspout and multiple vortex tornados are the main varieties. Waterspouts are spiraling funnel-shaped winds. They connect to a large cumulus or cumulonimbus cloud. Waterspouts are found generally in the tropical regions near the equator. With the exception of Antarctica, tornados have developed in all the continents. However, most of the tornados of the world occur in the North America, especially in the Tornado Alley region of the United States of America. Tornados occur in other parts of the world also, such as south and eastern Asia, South America, southeast Europe, southern Africa, southeastern Australia, etc.
Rating of Tornados
There are different rating systems for measuring the strength of tornados. They use different scales to rate the strength of tornados. Fujita Scale is one rating system. Fujita Scale rates the strength of tornados by estimating the damage caused. Now some countries use the Enhanced Fujita Scale. If it is an F0 tornado, it the weakest and it can damage trees but houses and structures may not be damaged. If it is an F5 tornado, it can cause devastation by ripping buildings off their foundations. Another rating system is the TORRO scale and it ranges from T0 for the weakest tornado to T11 for the highly devastating ones. Ground swirl patterns, Doppler radar data, photogrammetry, etc are studies for the rating of tornados.
Tornado Families and Outbreaks
In some situations, a single storm can cause a number of tornados. They may occur simultaneously or in succession. If a number of tornadoes take place from the same storm cell, they are collectively called a "tornado family". In some places several tornadoes may be spawned from a single storm system. If it occurs without a break, it is called a tornado outbreak. Sometimes in the same region tornado outbreaks may take place in successive days. It is an extended tornado outbreak and is often spawned by multiple weather systems.
Size and Shape of Tornados
Tornados can appear in different sizes and shapes. Generally, they appear in the shape of a funnel, a few hundred meters across. Often they are completely obscured by a cloud of dust and debris along with rain. They play havoc and can be devastatingly destructive. Landspouts which are relatively weak may appear as a small swirl of dust on the ground. Sometimes tornados may appear with a nearly cylindrical profile. They may be low in height and is called "stovepipe" tornado. There are also single-vortex tornadoes. They may appear like huge wedges stuck into the ground. Hence they are called "wedge tornadoes". Sometimes tornados in the dissipating stage may look like narrow tubes or ropes. They may even curl or twist into many shapes. They are called “rope tornados” or “roping out tornados”.
Color and Appearance of Tornados
Color and appearance of tornados may vary depending on the environment in which they form. If it is a dry environment, the tornado may be almost invisible. It may be a little obscured by swirling debris. If it does not pick up much debris as in the case of condensation funnel, the color may be gray to white. Waterspouts, moving over water bodies may appear white or even blue. If the tornado collects much of dust and debris, it may appear dark or in the color of the debris. Tornadoes in the snow-covered mountainous regions appear white and those in the Great Plains acquire a reddish color from the soil. The sources of light in the background also influence the color and appearance of tornados. If a tornado is viewed with the sun behind it (“back-lit”), it is found dark. The visual experience may be very different if the same tornado is viewed while the sun is behind the observer. Then it may appear gray or brilliant white. Tornadoes viewed in the background of setting sun may appear in dazzling colors.
Rotation and Sound of Tornados
Most of the tornadoes rotate cyclonically. They rotate clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. However, very few of them rotate in the anticyclonic direction. Tornadoes produce sounds which are caused by multiple mechanisms. The sounds may be of a wide variety; some may be of a jet engine, freight train, waterfall or a combination of these. The atmospheric conditions have a direct impact on the audibility of tornados. Some are not audible from a distance. The sound is caused by the winds of the tornado vortex. Also the airflow interaction with the surface and the debris has a role in the sound generation. Sound cannot be a sure warning for the coming a tornado because for many tornados sound may not be audible from a distance.
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