- Education and Science
Videos, Photos and Facts About Tornadoes
Tornadoes are the most destructive storms on this planet. Their violent, high winds have been known to wipe out entire towns in just minutes. According to the National Severe Storms Laboratory, about 60 people are killed by tornadoes every year. Just recently, on June 17, 2010 the state of Minnesota experienced deadly tornadoes. Two different EF4 tornadoes took the lives of two people and another EF4 tornado wiped out buildings and injured 30 in Wadena, located in West Central Minnesota.
A tornado occurs during a thunderstorm when warm air quickly rises and cold air stays at the Earth's surface. This creates winds from two different directions and they collide and begin to spin. The updrafts cause the funnel cloud to become vertical. The funnel cloud then reaches the bottom of a cumulonimbus cloud. When the funnel cloud reaches the ground that's when it becomes a tornado. There are many other factors involved in how exactly a tornado forms, some of which scientists are still trying to understand.
Tornadoes are classified by using the Enhanced Fujita Scale (EF). This scale rates the strength of a tornado based on the damage it causes. As of February 1, 2007 the Enhanced Fujita scale was implemented in place of the original Fujita Scale that was developed in 1971.
EF0 (gale tornado) - wind speed: 65-85 miles per hour (mph). Causes minor damage that can tear off tree branches, damage sign boards and chimneys.
EF1 (moderate tornado) - wind speed: 86-110 mph. Causes moderate damage that can overturn mobile homes and push moving vehicles off the road
EF2 (significant tornado) - wind speed: 111-135 mph. Causes considerable damage that can demolish mobile homes, uproot large trees, lift cars off the road
EF3 (severe tornado) - wind speed: 136-165 mph. Causes severe damage that can damage large buildings, destroy well-constructed houses, overturn trains
EF4 (devastating tornado) - wind speed: 166-200 mph. Causes extreme damage to near total construction that can completely level well-constructed houses and its frames, blow off structures with weak foundations, throw cars
EF5 (incredible tornado) - wind speed: over 200 mph. Causes total destruction. An EF5 tornado can badly damage reinforced steel concrete structure and lift houses off of their foundation and carry them through the air.
About 2% of the 1000 tornadoes that occur each year are categorized as EF4 or EF5.
There is no official National Weather Service definition of the area delineating Tornado Alley but it is a term that is often used to describe where most tornadoes in the United States occur.
Tornado Alley is located on the Plains between the Rocky and Appalachian Mountains. According to the Storm Prediction Center, 90% of tornadoes hit this region because cold, dry air from Canada and the Rockies meets warm, moist air from the Gulf of Mexico and hot, dry air from the Sonoran Desert, which combines with atmospheric instability to produce intense thunderstorms.
Fast Facts About Tornadoes
- Tornadoes can take place in any state in the U.S.
- Texas has had the most tornadoes, followed by Oklahoma and Kansas
- The strongest ground level wind speed ever recorded was 318 mph in 1999
- The current average time to warn people of a coming tornado is 11 minutes
- The deadliest tornado killed 695 people in 1925
- 1000 tornadoes occur in the United States every year
- Typically, tornadoes only last for a couple of minutes
- On average, tornadoes are around 500 feet across and stay on the ground for 5 miles
- Tornadoes normally rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere
- Although they can happen any time of the year, peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer
- Tornadoes are most likely to occur between 3:00 and 9:00 p.m.
- The average forward speed of a tornado is 30 mph and can reach speeds up to 70 mph
- Tornadoes are also called cyclones or twisters
Close Call - Storm Chasers in South Dakota
Have you ever seen a tornado or been in one?
Tips to Stay Safe During a Tornado
Danger signs of a tornado:
- Dark, greenish sky
- Large hail
- Tornado sirens
- Large, dark, low-lying cloud
- Rotating clouds
- Cloud of approaching debris
- It is suddenly still and quiet
- Loud roar like the sound of a freight train
If you are in a building structure such as your home, a shopping center, an apartment building, etc. seek shelter in the basement or cellar. If none such place exists, go to the lowest level and find the center of most interior room (like a hallway, closet, etc.) Get away from corners, windows, doors and outside walls.
If you are in a vehicle, trailer or mobile home get out as quickly as possible and go to the lowest floor of a nearby building.
If you are outside with no protection lie flat in a nearby ditch and cover your head with your hands.
Some things to remember:
- If you're outside, do not go under an overpass or bridge
- Don't try to outrun a tornado, especially if you are in a congested or urban area - you are safer outside of your vehicle in the appropriate shelter
- Be wary of flying debris, which is how most people are injured or die in tornadoes
- Even if tied down, mobile homes offer little protection from tornadoes
- Do not try to open windows
Twister - the Movie
Remember Twister? The movie with the flying cow? In the movie, Helen Hunt and Bill Paxton were storm chasers looking for a way to to put their equipment (which they called Dorothy) in the path of a tornado in the hopes that the sensors would fly up into the tornado and collect data. The idea wasn't that far-fetched as it was based on work done by the National Severe Storms Laboratory (NSSL) in the mid 1980s. They called their equipment TOTO (TOtable Tornado Observatory).
The NSSL tried for many years to put TOTO in the path of a tornado but had minimal success. They did not however have the sensors to fly up in the tornado, as in the movie. Although they claim, "that is not a bad idea and with all the advances being made in computer technology, we might be able to do that someday."