On April 26th of 1991 university of Oklahoma researchers measured 287 mph winds at about 600 feet above the ground in a tornado in northern Oklahoma, using a portable Doppler radar. This was the first time direct measurement of winds in a tornado of that intensity had ever been made. These are the strongest winds ever directly measured in a tornado. These two cases are actual measurements, but otherwise, no wind measuring equipment has ever survived a direct hit from a violent tornado. Other than these few cases of direct measurements, tornado wind speeds must be estimated from the study of damage left in their wake.
Tornadoes do their destructive work through the combined action of wind and windblown debris.
In one of the most common cases, the roof is peeled off or wind enters the structure through a large window or door, such as a garage door, blown in by the winds. The appearance to someone outside the structure is that the building has exploded. The damage pattern can vary widely from one home to the next based on factors such as shape, building quality, orientation relative to the direction of the wind, the amount and size of windblown debris, and the intensity of the tornado itself. An important point to remember is that while most tornado damage is caused by the violent winds, most tornado injuries and deaths are caused by flying debris. Wood splinters, glass, lawn furniture, or even cars can become deadly missiles when driven by tornado force winds.