What is a Tornado? Facts and Pictures

Dictionary.com defines a tornado as "a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.

The word "tornado" originates from the Latin word "tonare", which means "to thunder." That word then became the Spanish word "tronada" which means thunderstorm. English speaking people then starting pronouncing the word in the form we use today - tornado.

In the U.S. tornadoes are also called twisters.

The United States leads the world in the number of tornadoes annually, but only because of its size. Measured by tornadoes per acre, the U.K. the has the highest number of tornadoes annually, though the majority are relatively weak. (NOAA)

Tornadoes occur on all continents except Antarctica. North America's millions of acres, different climate zones and topographical features make it a prime breeding ground for tornadoes.

Climatologists have two categories which classifies tornadoes by how they are created: supercell and non-supercell.

Supercell

These tornadoes are formed along with violent thunderstorms. They are the strongest and most dangerous, with windspeeds sometimes reaching over 200 mph.

The vortex of winds in a supercell is not considered a tornado until it touches both the base of the "mother" cloud and the ground. Until then the vortex of winds is called a funnel cloud.

Non-supercell

Non-supercell tornadoes are divided into three types.

• Gustnado, also known as a dust devil or whirlwind: It is formed by gusts of wind in front of a storm front. It is a forms on or just above the earth's surface.
• Landspout: This is a tornado with a thin, rope-like vortex that forms before a storm. The rotation starts on the ground, and is not caused by updrafts of air.
• Waterspouts: They are landspouts which are formed over surfaces of water.

For a tornado to form, certain atmospheric conditions must be present: adequate low-level moisture, an unstable atmosphere, and clashing cold and warm weather fronts.

This three conditions make the atmosphere ripe for violent weather.

Stable vs unstable atmosphere

According to Meteorologytraining.tpub.com, "The atmosphere has a tendency to resist vertical motion. This is known as stability."

A stable atmosphere keeps air flowing horizontally, even when the air flow is disturbed. An unstable atmosphere allows air flow to develop both horizontally and vertically. This results in unstable air.

Clashing weather fronts

When a cold weather front meets a warm weather front with plenty of moisture, the warm, moist air, being lighter then the cooler air, rises. As the warm air rises, it meets cooler air and condenses, which forms moisture-laden thunderhead clouds.

The rising air will meet winds coming from different directions at various altitudes. These upper level winds will cause the rising air to spin, at first horizontally, then vertically as the air rises faster and faster. A tornado has been born.

The Fujita scale classifies tornadoes on a scale of 0-5 based on the speed of a tornado's winds and the damage caused by those winds. The scale is named after Dr. Ted Fujita, a scientist who developed the scale in 1971.

The Fujita scale has since been revised by experts and is believed to be much more accurate. The new scale, adopted by meteorologists in 2007, is known as the Enhanced Fujita Scale. It is known more commonly as the EF scale.

Since there is yet no practical way to measure the wind speeds inside a tornado, scientists estimate the wind speed by examining structural damage done by tornadoes.

Scientists and meteorologists will also look at the marks a tornado leaves on the ground, consider eye-witness testimony, video evidence and radar images to rate a tornadoes severity.

• Oklahoma City, OK has the honor of being the US city that has been most hit by tornadoes - 100. Huntsville, Alabama is second.
• Only 2% of tornadoes cause 70% of the deaths. These are the tornadoes with wind speeds greater than 200 mph, and which can last longer than one hour.
• Tornadoes rotate counter-clockwise in the northern hemisphere, and clockwise in the southern hemisphere.
• 695 people were killed and more than 2,000 injured by the single most deadly tornado on record. This tornado lay down a trail of devastation for 219 miles across parts of Missouri, Illinois and Indiana on March 18, 1925.
• The record for most tornadoes in a single month was 543 tornadoes, set in May 2003.
• Houses do not explode or implode because of pressure changes in a tornado. They are destroyed by the winds.

• Florida has more twisters per square mile than any other state.
• Tornadoes kill an average of 70 people a year in the U.S.
• The deadliest outbreak of tornadoes killed 308 people on April 3, 1974. The two-day outbreak of 147 tornadoes occurred across 13 states.
• A single tornado can be one mile wide.
• May is the month which has the most twisters. June is second.
• It is an old wives' tale that the safest place to be during a tornado is in the southeast corner of your basement. The safest place is in an interior room on the lowest level of your home.
• The tornado that affected the most people world-wide occurred in Bangladesh on April 26, 1989. It killed 800 people and injured or displaced 102,000.

A tornado watch is issued for your area if conditions are right or may become right for the development of tornadoes.

A tornado warning for your area means a tornado has been spotted or is being shown on radar. You should seek immediate shelter.

I have lived both in the Midwest and on the East Coast of North America. I have witnessed and lived through a few hurricanes. They are scary storms, sending millions of people fleeing from their path. Listening to a hurricane beat against your house for hours, even days, is nerve wracking.

The biggest difference between the two, in my opinion, is that you have at least a week's warning when a hurricane is coming. When a tornado appears, you have minutes, not days, to get out of its destructive path.

In hurricanes more people die because of the storm surge and flooding, something that can be predicted with some accuracy and from which a person can evacuate from before hand. Twisters kill with their deadly winds.