Tornadoes: the phenomenon that has devastated the eastern United States, in three keys

The tornados are a common meteorological phenomenon in U.S, sometimes devastating, but whose origin cannot yet be fully explained. This Friday night, Kentucky and other states in the east of the country have suffered a wave of about 30 tornadoes classified as the event of its kind “most severe in history“.” In the United States there are usually more tornadoes than anywhere else in the world, although they can occur almost anywhere, “says the US National Weather Service (NWS). Great American plains states like Kansas, Oklahoma and even Texas is particularly affected.

These are some of the keys of this type of meteorological phenomena:

Scientists still don’t fully know the mechanism behind the formation of a tornado. “The mystery remains great around tornadoes. They are rare, fatal and difficult to predict“explains the National Severe Storms Laboratory of the United States National Oceanic and Atmospheric Agency (NOAA).

What is known, however, is that they are generally the result of calls supercell storms, which are characterized in particular by strong updrafts, says NOAA.

Inside the storm, a strong vertical wind current causes the appearance of a cylinder that rotates horizontally on itself. The upward air currents lift the rotating cylinder inside the supercell. The rotating air column becomes thinner, often spreading in the form of funnel, Y spinning faster and faster to form a tornado, also details NOAA.

“Tornadoes grow extremely fast and can dissipate just as quickly,” according to the NWS. “Most tornadoes make landfall during less than 15 minutes“, keep going.

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A very violent phenomenon

“Tornadoes are the more violent storms of nature, “notes the NWS. Winds can reach almost 500 km/h, with damage reaching almost two kilometers wide and about 80 km long for each tornado.

According to NOAA, more than 50 people die each year in the United States as a result of tornadoes.

Spring 2011 was the deadliest tornado season in the United States, with more than 580 people killed between April and June. The damage bill rose to $ 21 billion.

Once a tornado has passed, scientists assess its strength by looking at the damage caused and associating it with the observed gusts. They then rank it using the improved scale of Fujita, which includes six grades -from 0 to 5-. The lower level (0) represents light damage with gusts between 100 and 135 km / h, and the upper level (5) represents “incredible” damage with gusts greater than 320 km / h.

How to act in the event of a tornado

Despite advances in weather predictions, tornado warning times are often short. The most important thing is to plan in advance how to react. In regions where tornadoes normally occur, tornadoes are performed drills and the houses have shelters underground to hide while the storm passes.

According to the US Federal Emergency Agency (FEMA), it is essential to have the shelter equipped with flashlights and spare batteries, a portable battery-powered radio, a first aid kit, food and water.

If you lack shelter, it is advisable to be in a windowless area of ​​the house or to crawl under a sturdy piece of furniture, such as a desk. If you are on the street, it is recommended to enter a sturdy building. If this is not possible, find a ditch or area at a low level and protect your head and neck with your arms. If you were traveling by car, you must get out of the vehicle immediately and seek shelter.

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