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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 . 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 . 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.〔Grazulis, ''Significant Tornadoes'', 143–45; 147–48.〕 ==List of events== The tornadoes on this list have been officially rated F5 by an official government source. Unless otherwise noted, the tornadoes on this list have been rated F5 by the National Weather Service (NWS), as shown in the archives of the Storm Prediction Center and National Climatic Data Center (NCDC). Prior to 1950, assessments of F5 tornadoes are mostly based on the works of Thomas Grazulis. Between 1880 and 1950, the NCDC accepted 38 of his classifications as F5s. In addition to the accepted ones, he rated a further 25 during the same period.〔 From 1950 to 1970 tornadoes were assessed retrospectively, primarily using information recorded in government databases, and newspaper photographs and descriptions. Beginning in 1971, tornadoes were rated by the NWS using on-site damage surveys. For United States tornadoes as of February 1, 2007, the Fujita scale has been recalibrated to more accurately match tornado speeds with their damage and to augment and refine damage descriptors. The new system is called the Enhanced Fujita scale. No earlier tornadoes will be reclassified, and no new tornadoes in the United States will be rated F5. France and Canada later adopted the EF-scale in years following. In all, 51 tornadoes have been officially rated F5 since 1950: 50 in the United States and 1 in Canada. The works of Grazulis also revealed 16 more F5s between 1950 and 1995, with four later being accepted by the NCDC.〔 Since the implementation of the EF-scale, there have been 9 officially rated EF5 tornadoes in the United States. – Official F5/EF5; undisputed – Rated F5/EF5, or mentioned as a possible F5/EF5 by tornado expert Thomas P. Grazulis – Listed as an F5/EF5 on the 2000 NCDC tornado climatology memo – Official F5/EF5, but rating is disputed; event may not have been F5/EF5 – Officially ranked below F5/EF5, but rating is disputed; event may have been F5/EF5 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「List of F5 and EF5 tornadoes」の詳細全文を読む スポンサード リンク
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