The Anatomy of a Tornado

Tornados are some of the most violent storms on Earth with the winds spiraling around them sometimes exceeding 100 mph and some have even exceeded speeds of 300 mph. In the U.S., an average of 1000 tornadoes are reported each year and they usually kill around 60 people.

The three conditions required for thunderstorms to form are moisture in the lower to

middle levels of the atmosphere, unstable air or air that continues to rise from near the ground and a lifting force or something needed to lead the air once it begins to rise. Heated air near the ground is the most common cause of Tornados. When the air warms it rises easier and advances lots of cool air, which forces warm air upwards triggering thunderstorms.

When all conditions are present, moist air rises high into the sky and then cools and condenses into high clouds, which eventually form lightning storms. The air, which rises in a thunderstorm, is called an updraft. The Tornados are formed in the updrafts.

The strongest Tornadoes are often near the edge of the updraft, not far from where the air is descending in a downdraft caused by the thunder, falling rain and hail. This is why a burst of heavy rain or hail sometimes announces a Tornado's arrival.

Tornados are often mostly found in the Nations' Midwest in an area stretching from Texas to Nebraska that also includes Colorado, Iowa, Illinois, Indiana, Missouri and Arkansas, known as Tornado Alley. Tornados have occurred in all 50 U.S. states and are actually more common in Florida than in Oklahoma.

Tornados rank according to the amount of damage in which they cause according to the six levels of the Fujita Scale. F0 and F1 tornadoes on the scale are considered to be "weak" and cause minimal to moderate damage with winds of 40-112 mph. F2 and F3 tornadoes are considered to be strong, packing winds of 113-206 mph that can cause severe damage. The most violent tornadoes are classified as F4 to F5 with winds of more than 206 mph. Damage is extreme to catastrophic.

Most weak tornadoes last 10 minutes or less, traveling short distances. Violent tornadoes have been known to last for hours and some have traveled more than 100 miles.

How are Tornados formed?

Exactly how tornadoes are formed is not yet fully known. But after many years of study, meteorologists, who are researchers who study the weather, know some things for sure.

Tornados may form due to several different types of storms, but they are often produced in the more powerful thunderstorms.

Tornados form where warm, moist air and cold, dry air meet and begin creating updrafts which develop into a massive rotating cumulonimbus clouds and sometimes a spinning column of air known as vortex forms in these clouds. When this vortex becomes visible and reaches the ground, a Tornado is created.

But not all tornadoes form as part of a thunderstorm. Meteorologists have found that sometimes a horizontal layer of air sometimes begins to spin. This happens when it becomes caught between two thin layers of air that move in opposite directions. This is similar to rolling a pencil between your hands. With the help of the updraft this column becomes vertical and extends to the ground to form a tornado.

How big are most Tornadoes?

Tornados are spin tops, which spin on an axis while they are moving across the earth's surface. Tornados also vary in size as well. They are, on average, between 130 to 170 meters (400-500 feet) wide and can travel between 35 to 90 kilometers per hour (20 to 50 mph) over the ground. These tornadoes usually last for several minutes and can cut a path of destruction a couple of kilometers long. The most devastating Tornados are nearly 2 kilometers (a mile) long but they are also the most rare. Their winds can exceed 250 mph) and can last for up to three hours while traveling at over 70 mph.

The word Tornado comes from two Spanish words, Tronado meaning thunderstorm and Tornar meaning to turn.