A tornado is one of the most violent of all storms. It is a destructive spinning column of air that extends from a thunderstorm. By definition, a tornado also has to touch the ground; a spinning column of air that doesn’t touch the ground is called a funnel cloud.
What Causes Tornados?
Scientists are still not entirely sure what causes tornados – and the question is complicated by the fact that there are different types.
The most common type of tornado, unfortunately, is also the most dangerous and destructive type. It develops from a type of thunderstorm called a supercell that typically contains a rotating updraft, with an updraft being an air current traveling upward.
Scientists are still not sure what causes air currents to start spinning. According to one hypothesis, the rotation is caused by wind shear. In wind shear, air currents at two different levels above the ground start blowing in different directions or at different speeds.
For example, a wind that is just above the ground and is consequently slowed by friction may be blowing from the southeast at five miles an hour. At 5000 feet above the ground, the wind might be blowing from the southwest at 25 miles an hour. The two air currents form a spinning tube of air. At first, the funnel cloud spins horizontally, but it eventually tilts to a vertical position. When it touches the ground it becomes a tornado, and the moist, warm air just above the ground fuel it.
Researchers still have a lot of questions about the formation of tornados. For example, they have noted that only 20 percent of supercells form tornados. What makes those supercells different from the 80 percent that don’t form tornados? What causes air currents in a supercell to move at different speeds or in different directions?
And what about tornados that form in thunderstorms that aren’t supercells?
Non-supercell tornados are just that: tornados that form from a storm that isn’t a supercell. They generally develop in areas that are sparsely populated, so researchers have had less opportunity to observe them. The ones they have seen have usually been smaller than supercell tornados.
Non-supercell tornados develop when a wind shear collides with a small column of spinning air and causes it to grow. For example, eastern Colorado gets non-supercell tornados when cool air from the Rocky Mountains collides with the dry and hot air over the plains.
Scientists have identified at least three types of non-supercell tornados: gustnados, waterspouts, and landspouts.
Gustnados don’t even have a tornado’s characteristic funnel. They form along a storm’s gust front at or just above the ground and develop into whirls of debris or dust.
Waterspouts and landspouts both have ropy and narrow funnels that develop from a still-growing thundercloud that doesn’t produce a rotating updraft. They start spinning near the ground or surface of the water.
Which Countries Get the Most Tornados?
The United States, which experiences over 1200 tornados a year, leads the pack by a significant margin. It also tends to have many of the strongest and most violent tornados. There is even a region in the US called Tornado Alley. While authorities have not agreed on its exact borders, it generally includes the states Texas, Oklahoma, Nebraska, Kansas, South Dakota, Iowa, and Missouri. Some experts add Indiana, Illinois, Minnesota, Wisconsin, and western Ohio to the list of states in Tornado Alley.
Tornado Alley owes its unfortunate distinction to its geography. It gets cold and dry air from both Canada and the Rockies as well as warm moist air coming north from the equator. The mixture spawns the type of storms that produce tornados.
Canada gets the second-highest number of tornados per year with about 80 to 100 tornados every year. Most of them occur in Ontario or the plains.
The United Kingdom experiences over 30 tornados every year. Because of its small size, that means it has more tornados per area than any other country. Most of the tornados develop along the Thames or in western England near the Welsh border. Fortunately, most tornados in the UK are relatively weak.
Other countries that get a lot of tornados include Argentina, Bangladesh, Uruguay, Brazil, New Zealand, South Africa, and the Philippines. Tornados also occur frequently in parts of Asia and Europe, as well as northern Mexico.
Why Does the United States Get So Many Tornados?
The US owes its distinction as Tornado Central to geography since it is home to both the Gulf of Mexico and the Rocky Mountains. These geographical features produce the conditions needed to create the ingredients for severe thunderstorms that spawn tornados:
- Cool and dry air at high altitudes
- Warm and moist air near the ground
- Horizontal winds that rise from the ground and change direction as they do so
Most of the United States also falls in the middle latitudes between the tropics and the polar regions. Whether above or below the equator, regions that fall between 30 and 50 degrees tend to produce a lot of tornados. Such regions get warm tropical air colliding with cold polar air. The different air currents tend to move at different speeds and in different directions, and that can lead to the development of a thunderstorm with rotating air in it. That rotating air can form a funnel cloud or tornado.
What Is the Enhanced Fujita Scale?
The Enhanced Fujita Scale (EF-scale) is a modified version of the Fujita Scale. While the original was introduced in 1971, the Enhanced Fujita Scale was adopted in 2007. Both scales measured a tornado’s intensity by its speed and destructiveness, but the EF-scale was based on several additional decades of research and observations that better matched a tornado’s wind speed with the damage it caused.
The EF-scale still uses the same ranking as the original. There are six possible ranks with EF0 being the weakest and EF5 being the strongest.
The EF-Scale also uses a list of 28 Damage Indicators (DI) that describe the amount of damage done to a given type of structure or tree.
Where Was the Biggest Tornado?
Not only does the United States get the most tornadoes, but it also gets the biggest tornados. The biggest tornado ever recorded was the El Reno Tornado of 2013. It was a colossal 2.6 miles (4.2 kilometers) wide and tore through Oklahoma’s Canadian County during a 40-minute period. It also reached speeds of over 300 miles per hour. The tornado killed eight people and injured 150 others.
Other massive tornados include the Hallam Tornado of 2004, the Mulhall Tornado of 1999, the Bridge Creek-Moore Tornado of 1999, and the Tri-State Tornado of 1925. All of them hit areas within Tornado Alley.
How Can You Determine A Tornado’s Width?
Scientists have two ways of measuring a tornado’s width. The first and older method is to measure the width of the path left by the tornado. This is still the most common method. The newer method involves using Doppler radar. While it may be quicker and more precise, powerful tornados can easily destroy weather instruments.
Where Was the Deadliest Tornado in the World?
While the United States has the most tornados and the biggest tornados, the deadliest tornados tend to occur in Bangladesh. Nearly half of the ten most lethal tornados in the world occurred there.
The Daulatpur-Saturia Tornado, which was the deadliest tornado in the world ever recorded, took place on April 26, 1989, in Bangladesh’s Manikganj District. Over 1300 people perished, and 12,000 others were injured. The tornado also destroyed the homes of 80,000 people. A newspaper reported that the devastation was so total that only a few trees were left standing; everything else had been destroyed. The tornado tore through about 50 miles between Saturia and Daulatpur.
Another devastating tornado struck Bangladesh in 1973. It annihilated nine villages, killed 681 people and injured countless others.
Other deadly tornados in Bangladesh include the following:
- 1969 East Pakistan Tornado – 660 fatalities
- 1964 Magura and Narail Districts Tornado – at least 500 fatalities; seven villages destroyed
- 1977 Madaripur and Shibchar Tornado – 500 fatalities; all buildings and trees in the area were destroyed
The second-deadliest tornado in the world did take place in the United States. It became known as the Tri-State Tornado because it swept through parts of Missouri, Indiana, and Illinois on March 18, 1925. It killed 695 people and left 300 miles of destruction behind it. The Tri-State Tornado was also one of the biggest tornados anywhere, for it was a mile wide. The Tri-State Tornado also holds the record for duration; it lasted three hours and 37 minutes.
The Joplin Tornado was the deadliest tornado to strike the United States so far in this century. It occurred on May 22, 2011, in Joplin, Missouri. 158 people perished and over 1,000 were injured.
What Is A Tornado Outbreak?
Sometimes, a very strong thunderstorm will spawn more than one tornado. If it spawns several over 24 hours, the result is called a tornado outbreak.
The exact number of tornados required to earn the designation of “outbreak” depends on the region. In most places, an outbreak describes a storm that has produced at least ten tornados. An outbreak in Tornado Alley consists of at least two dozen strong tornados. On the other hand, if the storm takes place in an area like New England that has relatively little tornado activity, an outbreak consists of just six tornados spawned by the same storm.
What Was the Largest Tornado Outbreak?
The 2011 Tornado Super Outbreak was the largest outbreak ever recorded. It took place between April 25 and 28 and spawned a staggering 362 tornados.
The 2011 Tornado Super Outbreak covered nearly a third of the United States. Alabama was the most severely affected, but other states hit by tornados included Arkansas, Georgia, Illinois, Kentucky, Louisiana, Mississippi, Missouri, Ohio, Oklahoma, Tennessee, Texas, and Virginia.
The storm originated in Mississippi and spread to neighboring states. Alabama was hit the worst; it was struck by 69 tornados, including an EF-4 monster that was 1.5 miles wide and traveled over 80 miles while passing through Tuscaloosa and Birmingham. This one tornado killed 65 people and injured over 1,000 others. Tuscaloosa alone spent $100 million dollars on simply cleaning debris.
The outbreak produced 11 more EF-4 tornados and 3 EF-5 tornados. The first EF-5 tornado appeared outside of Smithville, Mississippi. It had a wind speed of around 205 mph, killed over a dozen people, and destroyed 18 homes.
What happened to Greensburg?
Greensburg, Kansas, is a small town famous for its rebuilding efforts. On May 4, 2007, a massive EF-5 tornado tore through the town, killing 11 people and destroying 95 percent of the buildings.
Local, state, and federal officials decided to emphasize using green technologies during the town’s reconstruction. For example, all of the electricity now comes from wind power. Greensburg also became the first town in the United States to install all LED streetlights.
The Arts Center became the first building in Kansas to earn a LEED-Platinum certification, with Platinum being the highest-rated and most stringent certification given by the US Green Building Council. Greensburg has more LEED-certified buildings than any other town of comparable size.
Ten years later, the citizens held an anniversary celebration that included a memorial service for the tornado’s victims and the unveiling of a new public sculpture. By that time, they had rebuilt The Twilight theater and the Big Well Museum. The latter is dedicated to Greenburg’s oldest attraction, the world’s largest hand-dug well, which dates back to the 1880s. Greensburg also now has a hospital, school, a John Deere dealership, and about a half-dozen restaurants.