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May 22, 2013 8:55 AM by Stephen Bowers

Tornado numbers and what those ratings mean

With all the talk about tornadoes following the massive and very powerful tornado that hit Oklahoma earlier this week, I wanted to give you an idea of how common tornadoes are in Colorado. 

We have accurate tornado records in the United States back to 1950, and from then to 2012 the National Weather Service in Pueblo says 1,950 tornadoes have hit within Colorado. Data shows that nearly all of Colorado's counties have experienced at least one tornado, and at least two of those tornadoes have occurred atop 14,000+ foot peaks. We know of tornadoes that have touched down on both Mount Princeton and, more recently, Mount Evans. Contrary to popular belief, mountains do NOT block tornadoes from hitting our area. Thanks to the National Weather Service in Pueblo for helping us gather tornado statistics for Colorado.

The United States is the tornado capital of the world. 61,029 twisters have hit within the U.S. since 1950. The majority of those tornadoes happen in the Central and Southern Plains and the Midwest.

While most tornadoes occur in the United States, they do happen elsewhere. Since 1950, 6,749 tornadoes have been reported across Europe. In Australia, over 1,200 tornadoes are known to have touched down since the first record of a tornado there in 1795. Tornadoes also have occurred in Asia and South America, though tornadoes in those areas are very uncommon.

The only continent where there is no recorded tornado is Antarctica. 

So what about this EF-5 rating we keep hearing about? That comes from the Enhanced Fujita Scale, which is used to measure the intensity of tornadoes. First, Dr. Fujita was a well-known tornado researcher at the University of Chicago. The scale describes the wind of a tornado based on the damage it produces and ranges from EF-0 to EF-5 and the wind speeds of those ratings are as follows: 

 

  • EF-0: 65-85 mph
  • EF-1: 86-110 mph
  • EF-2: 111-135 mph
  • EF-3: 136-165 mph
  • EF-4: 166-200 mph
  • EF-5: Over 200 mph
Damage surveys conducted by the National Weather Service using strict guidelines following years of testing suggest the intensity of the wind. The pattern in which the damage is laid is analyzed to determine whether that damage was caused by a tornado or straight-line winds. Following the damage surveys, the National Weather Service survey teams name the official category. The category can change, especially with a tornado with a long lifespan, since the survey will begin at the beginning of the tornado track and conclude at the end of the tornado track. What starts as a weaker tornado may be stronger later on its path.

 

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