Tornadoes: How The Fastest Winds on Earth are Rated

Oklahoma’s Winds: Tornado Categories

There are few meteorological events that are as awe-inspiring as tornadoes. These occurrences are a compilation of mother nature’s greats hits: jaw-dropping lightening, bone-shaking thunder, breath-taking cloud formations, roof-rattling hail, ground-soaking rains, and, of course, record-breaking winds. But how do we determine if the dust devil in the late morning is less impressive than the foundation-breaking storm at dusk? How do we quantify the power of a tornado?

In 1971 Japanese-born American meteorologist, Tetsuya Fujita, whose full name is Tetsuya Theodore Fujita, introduced the Fujita scale as a way to differential tornadic intensity and path area.  Mr. Fujita Tetsuya, born on October 23, 1920 in Kitaky?sh? City, Japan, developed a grid of intensity based on the severity of damage resulting from the high winds of a tornado. Mr. Fujita analysed tornadoes in a holistic manner, combining traditional data on temperatures and winds alongside photos and movies of damaged structures, swirling winds, drag and bounce marks on surfaces, and the observation of uprooted trees and detritus thrown.  Fujita hand-drew maps of the tornadoes’ track because he did not trust computers for such fine-scale work.

Through his diligent process, he developed the following rating scale for tornadic activity:

  • F0: winds of 43-74mph, with a width of 33-164 feet. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.
  • F1: winds of 73-112mph, width of 98-492 feet. Moderate damage. The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed.
  • F2: winds of 113-157mph, width of 360-820 feet. Significant damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; high-rise windows broken and blown in; light-object missiles generated.
  • F3: winds of 158-206mph, width of 660-1,640 feet. Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.
  • F4: winds of 207-260mph, width of 1,300 – 3,000 feet. Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.
  • F5: winds of 261-318mph, width of 3,600 feet. Incredible damage. Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air farther than 330 feet; trees debarked; steel reinforced concrete structures badly damaged and skyscrapers toppled.

 

The Fujita scale allows for F6 or even F7 events, these categories are entirely theoretical because structural damage cannot exceed the total destruction that constitutes an F5 tornado. The most destructive and highest speed tornado on record was categorized as an F5. The 1999 Bridge Creek-Moore Tornado holds the record for highest wind speed may have been an F6 event, due to winds surpassing the 319 miles per hour mark, however there was no way to accurately measure these speeds.

 

Mr. Fujita died November 19, 1998 in Chicago, Illinois, U.S. but left a lasting legacy through his work in categorizing tornadic activity.

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