Article

Tornadoes

  • Grades: 3–5, 6–8

Q: How are tornadoes formed?
A: Tornadoes are generally formed in a thunderstorm. Thundershowers this violent require a complex mix of environmental conditions but usually include: a) very warm, humid air, b) very cool, dry air to the west and south, c) air to the west trying to replace the warm, moist air (a front moving in), c) upper level (high in the sky) conditions that first hold down warmer air from rising and then later, a complete reverse in conditions that let the warm air rise very fast and very far, and d) an upper level wind stream to move the air away from the rising column. This sounds complicated, but it really boils down to warm, wet air driven east by a strong cold front and what we call instability. (Al Peterlin)

Q: What does the funnel of a tornado look like?
A: A tornado is a rotating column of air that reaches from a thunderstorm cloud to the ground. If it doesn't reach the ground, it's called a funnel cloud because it's shaped like a funnel. The color is dark because of dust and dirt pulled up into it from the ground. (Al Peterlin)

Q: How do tornadoes end?
A: Scientists know a lot about what happens in thunderstorms and tornadoes but still don't exactly know what causes them. We spend a lot of time trying to detect one and then sounding the warning. We use radar much like a physician uses X-rays to spot small things at the start of a tornado. We do know that thunderstorms, to become fierce, need warm, humid air near the ground, a stable layer of air above acting like a small cap, and then some trigger even farther above (called a short wave or layer of instability) to set the event in motion. Getting these in proper order lets a tornado form, and if even one or the others diminish, the tornado ends. (Al Peterlin)

Q: Which is more dangerous, a hurricane or a tornado? Why?
A: Deciding whether a tornado or a hurricane is more dangerous is difficult. They are both very powerful, but hurricanes are much much bigger and so they do far more damage. I guess I would say, then, that a hurricane is worse than a tornado. (Barbara McNaught Watson)

Q: How long does it take for a bad storm to turn into a tornado or hurricane?
A: A hurricane usually takes days to develop. The fastest a hurricane might form is in 48 hours or two days. If a cluster of thunderstorms already exists then it might only take a day. A tornado, however, is spawned from a thunderstorm. A thunderstorm takes about 30 minutes to form and reach maturity (when thunder and rain occurs). Some tornadoes, which are called "landspouts" over land and "waterspouts" over water, can develop during this stage. The stronger tornadoes are believed to come from thunderstorms that are rotating (or spinning) slowly. In these storms, it is believed to take about 45 minutes for all the ingredients to come together. That is not very long! (Barbara McNaught Watson)

Q: Have you ever been inside the "eye" of a hurricane or tornado? If so, what was it like?
A: I have never been in the eye of a hurricane or been too close to a tornado and I graduated from the University of Oklahoma, a school in the heart of the Tornado Belt. My wife has seen two tornadoes. I also have a friend, Dave Morris, who is a weather officer in the U.S. Air Force Reserves 920th Weather Reconnaissance Group, Keesler Air Force Base, Mississippi, and he regularly flies into the eye of hurricanes making scientific measurements. He says, "A hurricane flight is often more than just a bumpy ride. It can be a slam bang, stomach churning, spine jarring, heaving, yawing, pounding nightmare of a ride with pilots struggling at the controls and meteorologists straining to read their instruments." (Al Peterlin)

Q: Why do tornadoes form in the Plain States?
A: More tornadoes form in the central United States than anywhere else in the world. Over the Plain States, especially in the spring and sometimes fall, you will often find the right conditions for the formation of tornadoes. First, I'll explain what tornadoes are. Tornadoes are spawned from thunderstorms. To have thunderstorms, you must have moisture to form a cloud and fall as rain. The moisture over the plains comes from the Gulf of Mexico. Next, you need the air to be unstable, which means that once it begins to rise, it will continue to rise. As the day's sun beats down, the warm air, with its Gulf moisture, begins to rise. Hot, moist air rises just as you see steam rising out of a tea kettle. It cools as it rises even higher and condenses into clouds. A third ingredient to get a thunderstorm going is something that will focus where the air is rising, such as a cold front. Typically, over the plains (especially in the spring) you will get a clash of the warm, moist Gulf air from the south and the cooler, drier Canadian air from the north. The boundary between these two air masses is called a cold front. Often along the front is a line of strong thunderstorms. However, only one percent of all thunderstorms produce tornadoes. What makes the plains unique in spawning so many tornadoes is that it lies east of the Rockies. Air that descends off of these mountains is warm and dry, and helps to start a thunderstorm rotating. You need the winds to change direction with height in a clockwise manner to get a thunderstorm rotating. It is out of the rotating thunderstorm that the tornado descends down to the ground. In the plains, the winds near the ground blow warm, moist air from the south. Farther, off the surface, the wind turns southwest and then west as you encounter the dry, warm air from the Rockies. This combination with the cold front helping to trigger the thunderstorms makes tornadoes more common in the plain states. (Barbara McNaught Watson)

Q: How can you tell when to evacuate for a tornado?
A: For now we have to wait for a warning issued by the National Weather Service that is passed to schools through local television and radio stations. To receive warnings in the quickest time, schools can get a NOAA weather radio that provides warnings directly by the National Weather Service. You can ask your teacher if the principal has a NOAA weather radio in the office. (Al Peterlin)

Q: Do tornadoes hit large cities or only in open areas? If they do hit big cities, can they destroy very large buildings?
A: Tornadoes can indeed strike large cities and have in the past. Fortunately, the chance of a tornado hitting any one specific place is slim. Therefore, it is not often that cities are hit. There is much more open space and rural area for them to affect. About 80 percent of tornadoes are small with winds up to 115 m.p.h. Only about 2 percent of all tornadoes are considered violent, with winds over 200 m.p.h. If a violent tornado struck a big city, it could destroy large buildings. The safest place in a large building during a tornado is on the lowest floor toward the center. You should be in a small room with no windows, such as an interior bathroom, stairwell, or closet. This part of a building is often left standing when a tornado hits. (Barbara McNaught Watson)

Q: Have you ever experienced a tornado? Is it like the movie Twister or is it different?
A: I have never been IN a tornado. I have been in thunderstorms that have produced tornadoes, and they are pretty scary. Fortunately, most tornadoes have winds of 115 m.p.h. or less and do not do extensive damage. In the movie Twister, the tornadoes were stronger and of the kind that could be deadly if one did not take shelter in a basement or closet on the lower floor. While I thought much of the movie was well done and I enjoyed it, the last scene where they ride out the tornado attached to the metal post was not very realistic. While they might have survived such a ride, they would have been greatly injured by flying debris. For me, watching videos of tornadoes and experiencing the thunderstorms is as close as I'd like to get! One of my jobs is to survey the damage caused by tornadoes. There have already been 16 tornadoes in Maryland this year, though most have been small. I am always amazed at what they do. (Barbara McNaught Watson)

Q: How many tornadoes have been recorded in the United States over the last ten years?
A: On average, there were 760 tornadoes yearly in the United States 1950 to 1994. However, in the 1990s, the number of tornadoes each year was quite a bit higher closer to 1,000. The year 1992 was especially active with 1,297 tornadoes. The three most active months for tornadoes are April, May, and June, but tornadoes can occur in any month. Tornadoes also occur in other countries, but the United States is a principle area of occurrence. (Al Peterlin)

Q: What goes through your mind when a tornado hits?
A: When weather is "bad" enough to be severe or there is a possibility of a tornado, I have a great desire to be "part of the action." I love to watch thunderstorms, and I enjoy the stress of working during severe weather and getting the warning to the public in time to save lives. (Al Peterlin)

  • Subjects:
    Tornadoes, Weather Forecasting
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