Tornadoes: Masters of the Air
Grapefruit-sized hail pounds on the roof and you wake up from your afternoon nap. You dash to the window and you see a wall cloud dropping from the base of the storm… Almost immediately, the tornado sirens start blaring, and you shout to everyone “Get to the storm cellar ASAP!” You throw open the front door and race outside, dodging the hail. You pry open the door to the cellar open and everyone climbs inside, just in time for you to turn your head…to see the one thing that scares you the most, a huge tornado, at least a mile wide. You duck into the cellar just in time for the tornado to strike with its deadly force. While you wait in the storm cellar, you hear the tornado passing right over you. As suddenly as it started, it is soon over. The sirens sound the “OK” signal and you step out of the cellar to…nothing but a pile of rubble. Tornadoes are perhaps the most deadly things that nature can produce.
So, what exactly are these powerful, destructive whirlwinds? How do they form? How do you know if one is coming? Who studies them? What was the largest, most deadly tornado outbreak? Let’s find out…
How are tornadoes formed? First, even before the thunderstorm develops, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Next, rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical. Finally, an area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation. (NOAA, 13-15)
Sure, we know how they are formed, but what are they by definition? Anyone could say that they are rapidly rotating columns of air and debris, but that isn’t quite right. The technical definition of a tornado is a rotating column of air attached to or beneath a cumuliform cloud and is in contact with the ground. (Passante & Bologa, 60) As far as the debris is concerned, it is picked up after the tornado hits the ground. Pieces of homes, cars, basically anything can be debris in a tornado. Yes, even cows are picked up by tornadoes. Even with this, how are tornadoes measured?
Tornadoes are measured using the Fujita scale, created by Tetsuya Theodore “Ted” Fujita in 1971. Fujita, a Japanese – American meteorologist, developed the scale in order to rate tornado damage. The scale differentiates tornado intensity and links tornado damage with wind speed. (Ted Fujita, 3) The scale rates tornadoes from F0-F5. F0’s are the weakest, only producing light damage, which includes damage to chimneys, branches broken off trees, shallow-rooted trees pushed over, and sign boards damaged. In an F0, the wind speed is estimated to be less than 73 miles per hour (mph). (NOAA, 3) As we go up the scale, the winds get stronger, and there is more damage to the area affected.
F1’s are a tiny bit stronger than F0’s, but they produce more damage. F1’s produce moderate damage, which includes peeling the surface off roofs, mobile homes pushed off their foundations, and moving automobiles are blown off the road. (NOAA, 4) Wind speeds are estimated to be 73-112 mph in an F1.
F0’s and F1’s are considered weak tornadoes because they don’t produce a lot of damage. Of all of the tornadoes that happen in the United States, 69% of them are weak tornadoes. Also, weak tornadoes make up less than 5% of all tornado deaths. These tornadoes also have a lifetime, on average, of 1-10 minutes and the winds are usually less than 110 mph. (NOAA, 18)
Strong tornadoes also occur, and these include F2’s and F3’s. F2’s produce considerable damage, which includes roofs torn off frame houses, mobile homes demolished box cars overturned, large trees snapped or uprooted, ect. (NOAA, 3) F2’s have wind speeds up to 157 mph and a minimum speed of 113 mph.
F3’s are stronger than F2’s and, as such, produce more damage. F3’s have wind speeds of 158-206 miles per hour. At these speeds, severe damage is caused. Severe damage is defined by roofs and some walls torn off well constructed houses, heavy cars are lifted off the ground and thrown, ect. (NOAA, 4)
These strong tornadoes account for 29% of all tornadoes in the U.S. and they account for 30% of tornado related deaths. Also, their lifetimes are, on average, 20 minutes or longer and they have wind speeds from 110-205 mph. (NOAA, 5)
Violent tornadoes are the terrors of the skies. They are F4’s and F5’s and they are very destructive. F4’s produce devastating damage, which means that well contracted houses are leveled; structures with weak foundations are blown away some distance, ect. With wind speeds of 207-260 mph, it’s hard not to expect that something wouldn’t be destroyed. Even with the damage caused by F4’s, F5’s are basically the definition of damage.
F5’s are the strongest tornadoes on the Fujita Scale. F5’s produce incredible damage, destroying all most everything in its path. But, F5’s are known to produce some weird things, such as destroying a house and leaving the patio furniture exactly where the people left it.
F4’s and F5’s account for only 2% of all tornadoes and 70% of tornado related deaths. (NOAA, 22) Also, their lifetimes can exceed 1 hour. Even with this information, how do you know if a tornado is coming?
In the environment, there are 3 important clues that implicate that a tornado is coming. A wall cloud is usually the first sign of a tornado. A wall cloud, by definition, is a lowering of the rain free base of a thunderstorm. Wall clouds are often prior to tornado formation. Another sign of a tornado is hail. Hail is formed by strong updraughts and super cooled water droplets in a storm. In strong storms, the air is rising so quickly, that some of the inflowing water vapor doesn’t have a chance to freeze onto a solid nucleus, like a bit of dust or salt. (Henson, 75-76) The storm that spawns the tornado has strong up draughts, so the hail falls near the tornado, making it an environmental clue. Another clue is the sound the tornado makes when it is touching down. People say that is sounds like a freight train going past or a large swarm of bees. This clue is by far the scariest, as you know that the tornado is very close. Even with these environmental clues, how do you find out about a tornado, even if you aren’t there and who monitors the area and issues warnings? (NOAA, 30)
The National Severe Storms Laboratory (NSSL) and the National Oceanic and Atmospheric Administration (NOAA) monitors the weather, issue warnings and watches, and have programs that monitor weather phenomena from the ground. NOAA mainly prepares the forecasts and broadcasts warnings via the television, weather radio, ect. NOAA looks at weather data to determine whether a severe storm will hit an area and if it will produce a tornado. If NOAA sees a hook shaped area forming on the Doppler radar, they would issue a warning or a watch, depending on the strength of the rotation. Then the National Severe Storms Laboratory (NSSL) would pick up on the watch/warning that was issued, and have scientists in the area directly affected on the lookout for severe weather. The NSSL’s goal is to study and investigate all aspects of severe weather in order to improve severe weather warnings and forecasts in order to save lives and reduce property damage. (NSSL, 1) The NSSL helps deploy the Totable Tornado Observatory (TOTO), which helps scientists learn about what happens inside a tornado. The Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) is the largest tornado research project in history to explore how, when and why tornadoes form. (NSSL, 2) VORTEX is a team of storm chasers from all over the country that deploy weather instruments, such as TOTO, in order to study tornadoes. These government projects are intended to help keep us safe from the power of tornadoes. Even with this information, what was the deadliest tornado outbreak in U.S. history?
The deadliest tornado outbreak occurred on March 18th, 1925. The tornado that cause most of the damage was spawned NNW of Ellington, Missouri, to 10 miles NE of Princeton, Indiana. This tornado was not expected and when it struck, it was a powerful F5 tornado. It was a mile wide and destroyed everything in its path. Its range was from Missouri and went through a total of three states, giving it the name the Tri-State Tornado. It went through Missouri, Illinois, and Indiana, where it dissipated. The reason it is considered the deadliest tornado outbreak is because it took 695+ lives and made 3,000+ people injured in a space of 5 hours. The storm also destroyed15,000+ homes and caused $5-$50 million dollars in damage. The tornado was not rated back then, as the Fujita scale had not been invented. When scientists saw pictures decades later, they rated the tornado as an F5 because of all the damage it caused. (Sanders, 65)
So, what have we learned about tornadoes? Well, in the first place, we have learned that they are rapidly rotating columns of air attached to or beneath a cumuliform cloud and is in contact with the ground. Secondly, we have learned how they are formed. Thirdly, we have learned that there are environmental clues that warn us that a tornado is approaching. Also, we have learned that there are government projects that help to keep us safe from the power of tornadoes. Another thing we have learned is when and where the deadliest tornado outbreak occurred. And the most important thing we have learned about tornadoes is when you see one…run for your lives!
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Updated: 6:32 PM GMT on February 07, 2013
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