Tornadoes or twisters manifest as rapidly rotating funnels of air which extend from a thunderstorm and maintain contact with the surface of the earth. Tornadoes are extreme environmental events and often lead to property damage, injury, and death. Tornadoes travel for a few miles, have a width of about 250 feet, and record wind speeds below 110 mph.
Etymology And Definition
The word tornado comes from the term tronada, which is the Spanish word for a thunderstorm. The Spanish word has its origins in the Latin word tonare which translates to "thunder". A tornado is also sometimes called a twister or a cyclone. The word cyclone is used in place of a tornado in the regularly-aired 1939 film "The Wizard of Oz", which also uses the term twister. A 1999 tornado-related film called "Twister" uses twister as a synonym for a tornado.
A vortex is considered a tornado if it touches both the ground and the source cloud. Most tornadoes are deemed to be funnel clouds, although the definition of a funnel cloud remains disputed. Tornadoes mostly start as funnel clouds while not all funnel clouds end up as tornadoes.
How Are Tornadoes Formed?
Tornadoes are mostly associated with severe thunderstorms referred to as supercells. During an extreme storm, rainfall from a cloud creates a downdraft in the rear of the cloud. This downdraft (sinking air) picks up speed as it heads to the ground and carries with it the thunderstorm’s rotating mesocyclone. The mesocyclone, while descending from the cloud base, pulls in cold, moist air from the storm’s downdraft area. A rotating wall cloud is subsequently created from the convergence of moist air and warm air in the updraft. As the downdraft causes the mesocyclone to pull air from a small area on the surface, the updraft intensifies and forms a region of low pressure on the ground. The mesocyclone is subsequently stretched down in the shape of a condensation funnel that is visible. The funnel’s descent coincides with the descent of the downdraft which fans outwards creating a gust front capable of causing profound damage at a significant distance from the tornado. The funnel evolves to a tornado after minutes of the downdraft touching the ground. The tornado is powered by the inflow of warm moist air, and it grows until it attains maturity. This period can be as a short as several minutes or as long as over an hour, and it is when the tornado causes the most damage. The downdraft cuts off the tornado’s air inflow thereby weakening it and causing it to dissipate.
Appearance Of Tornadoes
Tornadoes occur in a variety of shapes and sizes, and they move along with the thunderstorms from which they extend. A tornado appears as a narrow funnel stretching a few hundred yards wide, and it packs a cloud of debris close to the ground. Tornadoes appear in a variety of colors ranging from gray, white, blue, red, or the color of debris. The color of a tornado depends on where it occurs. In dry environments, the phenomena may be almost invisible if not for the swirling debris at its base. A tornado viewed before sunset may take on yellow, pink, or orange hues. Lighting conditions also affect the appearance of a tornado. Factors which have an impact on a tornado’s visibility include darkness, rain, and hail.
How Many Types Of Tornadoes Are There?
- Multiple vortex: These types of tornadoes feature two or more vortices rotating around their individual axis as well as a common center. These vortices often occur in severe tornadoes, and they leave small sections of heavier damage in their wake. A multiple vortex should not be confused with a satellite tornado which appears as a smaller tornado near a vast and vigorous tornado extending from the same mesocyclone.
- Waterspout: This type of tornado commonly occurs over water. Researchers further subdivide this tornado into fair weather and tornadic waterspouts. Fair weather waterspouts occur more frequently but are less severe. This tornado extends from cumulus congestus clouds above tropical as well as subtropical waters. Tornadic waterspouts, on the other hand, are associated with adverse thunderstorms and are intense and dangerous.
- Landspouts: Landspouts do not form from mesocyclones and are characterized by short lifespans and relative weakness. Landspouts can, however, produce strong winds with a potential to cause severe damage.
Where Do Tornadoes Occur?
The impact of tornadoes has been felt in every continent apart from Antarctica. The phenomenon occurs most frequently in North America. In the US, a region known as Tornado Valley is named for the occurrence of tornadoes. This area includes the states of Kansas, Missouri, Texas, Nebraska, and Oklahoma. The tornadoes in this area take place during summer when it gets hot in the Great Plains. The State of Florida also experiences its own share of tornadoes associated with the frequent thunderstorms recorded in the area. Tornadoes are occasionally recorded in northwestern and southeast Europe, eastern and south-central Asia, New Zealand, Southern Africa, southeastern and Western Australia, and east-central and northern part of South America.
Intensity And Impact Of Tornadoes
In 1971, Tetsuya Fujita together with Allen Pearson created a system of rating tornadoes using the Fujita-Pearson Scale. It has since been gradually replaced by the Enhanced Fujita Scale which is used to classify tornadoes. Tornadoes based on this system range from a least damaging EF0 to a devastating EF5. Another scale known as the TORRO scale classifies tornadoes from a weak T0 to very intense T11. The weaker tornadoes occur more frequently while the severe tornadoes are only reported on occasion and cause massive damage.