What Is a Tornado? How Do Tornadoes Form?

(Last Updated On: July 26, 2019)
What Is a Tornado? How Do Tornadoes Form?

Tornadoes are a force of nature to be reckoned with. These unpredictable spirals can occasionally generate winds of over 200 miles an hour, strong enough to completely destroy heavy structures like cars and houses. When a tornado hits, the damage can be incredibly costly. So what is a tornado exactly? And how do these massive spirals form in the first place? Let’s break it down.

What Is a Tornado?

A tornado is essentially a rapidly spinning funnel of air. In order to officially be considered a tornado, this air vortex must be in simultaneous contact with the earth and a cumulonimbus cloud at the same time. Tornadoes are rated in severity on a wind speed scale called a Fujita Scale, named for Ted Fujita, a University of Chicago weather researcher, back in 1971. The scale varies from EF 0, classified as a Light Tornado with wind speeds of 65-85 miles per hour, to EF 5, where a tornado with wind speeds in excess of 200 miles per hour is classified as an Incredible Tornado.

Some notable F5 rated tornadoes occurring throughout US history include the Tri-State Tornado of 1925 that killed 625 people, the St. Louis Tornado of 1896 that was responsible for the death of 216 people, and the more recent Joplin, Missouri Tornado of 2011 that killed 158 people.

Tornadoes may alternately be more broadly classified as weak, violent or strong. Strong tornadoes comprise only a tiny chunk of annual tornadoes in the US, only about 2%, but are typically responsible for most of the death and destruction. A typical tornado will eventually grow to an average size of 660 feet wide, and they will generally move across the earth at relatively slow speeds of about 10-20 miles an hour, although they can periodically burst forward at much faster speeds from time to time. Most tornadoes last for less than 10 minutes, but a severe tornado can continue to exist for up to 30 minutes.

Tornadoes tend to attract a unique brand of thrill seeking researcher dubbed a storm chaser, who will often repeatedly endanger their lives trying to study these unique phenomenon in an up close and personal manner. They collect data that is otherwise impossible to obtain.

How Do Tornadoes Form?

Tornadoes require specific conditions in order to form. First, tornadoes can only form during thunderstorms. Secondly, the formation of the powerful vortex necessitates the clash of cool dry air, usually from Canada, with warm moist air, usually moving in from the Gulf of Mexico. A large tornado also must include unpredictable winds. The unique combination of ingredients required to create a tornado is the reason why tornadoes tend to occur quite randomly and can be so difficult to foresee.

A region of the US just east of the rocky mountains that stretches from the Midwest states of Iowa, Kansas, Missouri, Oklahoma, and Nebraska, all the way into southern Texas, has been nicknamed Tornado Alley. This stretch of land is particularly prone to tornadoes, especially between the spring months of March to May. This is largely due to the probability of the high mountain range to the West generating cold, dry wind that can easily clash with warm high pressure systems rolling in from the South with no major mountain range to stop them.

Because of the unpredictable nature of tornado formation, tornado alerts cannot be sounded with the same accuracy and advanced warning systems that modern day forecasters use to predict hurricanes. The average warning time for a tornado alert is 13 minutes. While this may not be enough time to fully inform everybody in the vicinity of the impending danger, it can still help save lives. Warning signs that signal that a tornado is likely to form or has already formed include dark greenish tinted skies, the presence of hail, and an audibly loud roaring sound.  

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