Tornadoes: Nature's Phenomenon A tornado is "a violent, destructive, whirling wind accompanied by a funnel-shaped cloud that progresses in a narrow path over the land." Sometimes, a tornado will happen so quickly that there is little or no sign before it starts. A tornado can have the strongest winds on earth, up to 300 MPH, and can cause "fantastic destruction and great loss of life, mainly from flying debris and collapsing structures." Scientists use "the Enhanced Fujita Scale" to give tornadoes different levels. They started with the Fujita Scale and started using the Enhanced Scale in 2007 because it uses "three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to 28 indicators." The old scale had "F0" for the weakest level; the new scale has "EF0" for the weakest level. The old scale had "F5" for the worst level; the new scale has "EF5" as the worse level.
Tornadoes: Nature's Phenomenon
What is a Tornado?
A tornado is "a violent, destructive, whirling wind accompanied by a funnel-shaped cloud that progresses in a narrow path over the land" (Merriam-Webster, Incorporated, 2012).
Tornadoes can develop in mere seconds and destroy everything in their path
Sometimes, a tornado will happen so quickly that there is little or no sign before it starts (Federal Emergency Management Association, 2012). A tornado can have the strongest winds on earth, up to 300 MPH, and can cause "fantastic destruction and great loss of life, mainly from flying debris and collapsing structures" (Snow, 2012).
How and What of Tornadoes
How, What
The National Severe Storms Laboratory studies tornadoes and says that tornadoes come from thunderstorms. Before the thunderstorm, the wind changes direction, becomes faster and becomes higher. Then it becomes an invisible spinning wind going horizontally in the lower atmosphere. While the thunderstorm is happening, air rises inside it and tilts the spinning air sideways so it is spins vertically. Then the spinning air becomes 2 -- 6 miles wide and stretches through a lot of the thunderstorm, and is where a tornado usually comes from. The area where the thunderstorm develops is usually free of rain although it is in a thunderstorm. Then in moments, a strong tornado can start and "touch down" on the ground (NSSL-NOAA, 1992).
B. Size and Shape
The National Severe Storms Laboratory says that there are many shapes and sizes of tornadoes. It shows three sizes and shapes. There are weak tornadoes that are 69% of all the tornadoes, cause less than 5% of all tornado deaths, last 1-10+ minutes and have less than 110 MPH winds. There are strong tornadoes that are 29% of all tornadoes, cause almost 30% of all tornado deaths, can last 20 minutes or more, and have 110-205 MPH winds. There are violent tornadoes, that are only 2% of all tornadoes, cause 70% of all tornado deaths, can last more than 1 hour, and have winds more than 205 MPH (NSSL-NOAA, 1992). The National Severe Storms Laboratory did not really talk about different shapes of tornadoes but the Tornado Project does. The Tornado Project says that "you can get an infinite variety of possible tornado shapes" because: the tornado's shape might keep changing from a skinny rope, to a wider spinning mass of air, back to a weaker tornado; sometimes we do not see all the tornado; the air flows inside the tornado keep changing and the thunderstorm can keep changing strength (Tornado Project, 1999).
C. Appearance
The Tornado Project says that that "you can get an infinite variety of possible tornado shapes" but the Project also talks about "skinny rope" tornadoes, wide and fat tornadoes, and water spouts, which are tornadoes over water (Tornado Project, 1999).
D. Rotation
Tornadoes start out rotating horizontally inside of thunderstorms, and then the "updraft" of air in the thunderstorm tilts the spinning air and makes it spin vertically (NSSL-NOAA, 1992). The vertically spinning air is usually what we see when we see a tornado. Tornadoes spin counter-clockwise in the Northern Hemisphere, except when there is a "rare anti-cyclonic tornado" that spins clockwise. In the Southern Hemisphere, tornadoes nearly always spin clockwise (Wiki Answers, 2012).
III. Different Levels of Tornadoes
A. Level System
Scientists use "the Enhanced Fujita Scale" to give tornadoes different levels. They started with the Fujita Scale and started using the Enhanced Scale in 2007 because it uses "three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to 28 indicators" (About.com, no date).
B. Least
The old scale had "F0" for the weakest level: the wind speed is 40-72 MPH and the damage is light, like tearing branches from trees, ripping out trees with shallow roots, damaging signs, traffic signals and chimneys (Brain & Lamb, 2012). The new scale has "EF0" for the weakest level.
C. Worst
The old scale had "F5" for the worst level: the wind speed is 261 -- 319 MPH and the damage is "incredible," with cars thrown through the air, houses destroyed and steel-reinforced concrete buildings seriously damaged (Brain & Lamb, 2012). The new scale has "EF5" as the worse level (About.com, no date).
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