April 20, 2014
A tornado is one of the few natural disasters that have taken place in the Midwest, but its effects can cause devastation that can be felt worldwide. Tornadoes destroy entire towns. In some cases they will level an entire block, but leave one house standing almost untouched. Their paths can be unpredictable, and cost of the destruction almost immeasurable. A major natural disaster such as this could wipe out people’s way of life and a food supply that helps to feed the world. In many cases flooding accompanies tornadoes. These super cell storms can drop several inches of water in a very short ...view middle of the document...
Tornadoes produce the highest wind speeds of any storm. These winds can be in excess of 300 miles per hour (Abbott, p264). Tornadoes can occur in many parts in the world including Australia, Europe, Africa, South America, and North America. They are more common in the United States than in any other part of the world. Nearly 70% of the world’s tornadoes occur in the central United States. Tornadoes have occurred in all 50 states (NOAA,nd). The United States averages more than 1,200 tornadoes each year. Texas gets the award for the most tornadoes each year. I am sure they are thrilled.
Tornadoes form in unusually violent thunderstorms when there is sufficient instability and wind shear present in the lower atmosphere. Instability refers to unusually warm and humid conditions in the lower atmosphere. With these conditions, air quickly moves upward and forms thunderstorms. Air in the lower troposphere is lifted until it becomes less dense than surrounding air. Once it is less dense, it rises on its own. The speed that is rises depends on the density difference between the air rising and the surrounding air (Haby, nd). Wind shear is the change of wind speed or direction at different heights in the atmosphere. As downdrafts of air within the storm start to block the updraft that is supplying the energy for the tornado, it begins to weaken. The severe thunderstorms which produce tornadoes form where cold dry polar air meets warm moist tropical air. This is most common in a section of the United States known as Tornado Alley. Tornado Alley is a term often used by the media to denote a zone in the Great Plains region of the central United States. This area includes parts of Texas, Oklahoma, Kansas, and Nebraska.
The most violent tornadoes spawn from supercell thunderstorms. Supercell thunderstorms are usually long lived and have a continuously rotating updraft of air. They can move in a large-scale rotation. This rotation within the mid-level of the supercell is known as the mesocyclone (Abbott, p259). This rotation spins around the updraft and creates the vortex. Supercells are known for producing large quantities hail, hard downpours, strong winds and powerful downbursts.
Dr. T. Theodore Fujita, a Japanese-born American meteorologist created the Fujita Scale, or F-Scale in 1971. It is a system of classifying tornado intensity based on damage to structures and vegetation. It ranked tornadoes on a scale from 0-5. This system was used for over 30 years until the Enhanced F-scale was developed and took effect February 1, 2007 (“Tornado Facts”, 2014). The Enhanced F scale now uses 28 damage indicators to determine the intensity of the tornado.
Tornadoes can strike quickly with little warning. Most times they move from the Southwest to the Northeast, but can travel in any direction. Tornadoes can appear almost completely transparent until the pick up dust and debris or until a cloud forms in the funnel. Tornadoes normally occur during the afternoon hours...