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Myth: "Tornadoes don't cross rivers." Although some landforms may influence the distribution of tornadoes, rivers do not have any clear effect on them. The great Tri-State tornado of 1925, the deadliest tornado ever recorded, crossed both the Mississippi and the Wabash Rivers.
Myth: "Open windows in your house to equalize pressure." Do not do this! Your house will not "explode" due to a tornado passing over it, and taking time to open windows merely reduces your ability to seek safe shelter in time.
Myth: "Get to (or away from) the southwest corner of the building for safety." Of course, the safest place to be is in an underground storm shelter, or a reinforced above-ground storm shelter. If neither is available, then the safest place in a building is in a small, reinforced room (such as a bathroom or closet) near the center of the building, on the lowest floor (preferably below ground).
Myth: "Tornadoes skip." Sometimes, the damage path of a tornado will result in demolition of several buildings, followed by several lightly damaged, followed by several more demolished. This gives the impression that the tornado "skipped" over the less-damaged structures. There are several possible explanations for this. One is that the surviving buildings were simply better-constructed. Also possible is that the orientation of the buildings resulted in varying degrees of vulnerability to the winds of the tornado. Finally, small eddies in the tornado's circulation can add or detract from the overall flow in the tornado's circulation. Longer breaks in a tornado's path suggest that more than one tornado was involved. Supercell thunderstorms go through cycles of tornado formation and decay. One supercell storm may generate several tornadoes during its own life cycle. For an example, see the map of the May 3, 1999 tornado outbreak across central Oklahoma.
Myth: "Mobile homes attract tornadoes." This myth probably came from the tendency of tornadoes to demolish mobile homes while leaving nearby structures only slightly damaged. Mobile homes can be severely damaged even by weak tornadoes, which tend to cause only minor damage to most other kinds of dwellings. If the mobile home is not tied down, it is vulnerable even to the winds of a not-quite severe thunderstorm, since such a building can be flipped over by winds around 50 mph.
There are several excellent Web sites for general information on tornadoes. Try these:
Storm Prediction Center: Tornado FAQ
National Severe Storms Laboratory: NSSL Weather Research and NSSL Tornado FAQ
Federal Emergency Management Agency: Tornadoes
NOAA: NOAA Tornado FAQ and NOAA Tornado Links
Twelve, as of 2012. See this page for details. It is important to remember that the (E)F-scale is somewhat subjective, which can lead to some disagreement between experts as to the true rating of a given storm. Also, most of these tornadoes were given ratings long after they occurred, based on surviving reports of the storm-related damage.
No. See our detailed explanation.
According to the NSSL mobile radar (then referred to as "Doppler on Wheels", yes. Those winds were measured several hundred feet above the ground, however, and speeds at the surface were probably somewhat lower, due partly to friction.
Please see the answer to this question in the SPC's FAQ.
People have described the sound of a tornado in many different ways, often depending on the intensity of the storm in question. Sometimes, it sounds like the rumble of a passing freight train; occasionally it is described as being like the whine of a jet engine as power is applied to it. People in shelters sometimes describe the sound of their house being destroyed as similar to the sound of large hail pounding on the roof.