Among the most violent known meteorological events are tornadoes. Each year, more than 2,000 tornadoes occur worldwide, with the vast majority occurring in the United States and Europe.In order to assess the intensity of these events, meteorologist Ted Fujita devised a method to estimate maximum winds within the storm based on damage caused; this became known as the Fujita scale. At the top end of the scale, which ranks from 0 to 5, are F5 tornadoes. These storms were estimated to have had winds in excess of 261 mph (420 km/h). Following two particularly devastating tornadoes in 1997 and 1999, engineers questioned the reliability of the scale. Ultimately, a new scale was devised that took into account 28 different damage indicators; this became known as the Enhanced Fujita scale. With building designs taken more into account, winds in an EF5 tornado were estimated to be in excess of 200 mph (320 km/h).
Since 1950, there have been 59 officially rated F5 and EF5 tornadoes in the United States and 1 F5 in Canada. Additionally, the works of tornado expert Thomas P. Grazulis revealed the existence of several dozen more between 1880 and 1995. Grazulis also put into question the ratings of several currently rated F5 tornadoes. Outside the United States and Canada, seven tornadoes have been rated F5: two each in France, Germany, and Italy and one in Russia. Several other tornadoes are also documented as possibly attaining this status.
Since structures are completely destroyed in both cases, the identification and assignment of scale between an EF4 tornado and an EF5 is often very difficult
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