10 Tornado Factoids

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Tornadoes remain deadly and relatively unpredictable, despite recent advancements in weather science.
• a tornado, or twister, is a violently rotating column of air that extends between the earth’s surface and a cloud, usually a cumulonimbus cloud.
• most tornadoes last for less than ten minutes
• large tornadoes usually last longer—around 30 minutes
• the most powerful twisters have wind speeds of more than 300 miles (483 kilometers) per hour, which can rip buildings off their foundations. They can be more than two miles (3.2 kilometers) wide, and can spin across the ground for dozens of miles.
• the more common tornadoes have wind speeds of less than 110 miles (177 kilometers) per hour, are about 250 feet (76 meters) across, and travel only a few miles before they dissipate.
• tornadoes kill an average of 60 people a year in the u.s., mostly from flying or falling debris.
• how a tornado forms? While tornadoes can differ in size, strength, and location, they all share certain characteristics. They are spawned from a type of rotating storm called a supercell thunderstorm.
• wind shear – when winds at two different altitudes blow at two different speeds creating wind shear
• updraft – warmed by the sun, buoyant air near the ground begins to lift a section of the horizontal vortex into a vertical position
• storm – the stronger of the two vortices created by the updraft becomes the heart of the thunderstorm. The other one dies.
• supercell – upper-level winds tilt the rotating updraft, called a mesocyclone. This allows the storm to keep growing as warm air is sucked into the storm away from the cool downdraft
• a supercell requires more: winds that increase in strength and change direction with height. “then the updraft tends to rotate, and that makes a supercell
• tornadoes have been observed on every continent except antarctica.
• they have been most documented in north america, where an estimated 1,200 strike the united states each year
• the most notoriously affected region in the united states, called “tornado alley,” includes the great plains states of kansas, nebraska, and the dakotas, as well as parts of texas
• in many countries, including the united states, canada, and continental europe, the strength of tornadoes is measured by the fujita scale or the updated enhanced fujita scale.
• an f0 or ef0 tornado damages trees but substantial structures are left unharmed; a tornado in the strongest category—f5 or ef5 —blows away buildings.
• tornadoes are much harder to forecast than hurricanes
• as computers get faster and data improves, forecasts may get more accurate.