A spinning funnel of air that can spin at speeds of up to 300 miles per hour (https://www.nssl.noaa.gov/). They can each cause millions in property damage, and about a billion dollars a year.
How A Tornado Forms
Scientists don't exactly understand how a tornado forms, but here's what they know. A tornado needs an unstable atmosphere and it needs to be moist. Then, when an cold and warm front meet the warm air from the warm front rises quickly, since it's less dense. This creates a thunderstorm, which may reach the supercell stage. A supercell is a long thunderstorm that has about equal updrafts(rising air since it's less dense than the other air) and downdrafts(sinking air since it's more dense than the other air). When winds form at two different heights, from the up and down drafts, and start blowing in opposite directions they start to spin horizontally. Lastly, when one end gets caught in a updraft it pulls the spinning funnel vertical, and you have your tornado.
Historical Tornado Examples
The Tri-State Tornado of Missouri, Illinois and Indiana touched down on March 18, 1925. It was rated a F5 on the Fujita scale, a scale which classifies the tornado on the damage it causes. This tornado killed 695 people and injured 2,027. It caused 17 million dollars in property damage!
The 2011 Joplin tornado touched down on May 22, 2011. This storm killed 158 people and injured 1,150. This storm caused 3 billion dollars in property damage. It was an F5 on the enhanced fujita scale, a updated scale that classifies tornadoes.
This is a picture of the damage the Tri-State tornado caused.
This is the damage the Joplin tornado caused.
How Are They Alike/Different
The historical Joplin 2011 tornado had much more money lost to property damage. This is because there many people had insurance that the insurance companies had to pay. There was also a higher death toll, almost 500 more people, and more injuries, about 1,000 more in the Tri-State tornado.
Impact On Human Life
Tornado sirens are used to warn people when a tornado is coming. People in places where where tornadoes are common usually have basements in their house. People know to go to the basement when a tornado siren is on. With the technology people have today, such as cellphones, they may have an app that tells them when a tornado is coming. Another form of technology when it comes to predicting tornadoes that plays a big part are weather satellite. They can show when it is probable a tornado may be coming in the near future, so people can prepare.