Scale Fujita ( F-Scale ), or Fujita-Pearson scale ( FPP scale ), is a scale for tornado intensity rating, based primarily on tornado damage caused to man-made structures and vegetation. The Fujita scale scale is officially determined by meteorologists and engineers after a survey of land or air damage, or both; and depending on circumstances, circle patterns (cyclical signs), weather radar data, witness testimony, media reports and damage images, and photogrammetry or videogrammetry if movie recording is available. The Fujita scale was replaced with the Fujita Improvement scale (EF-Scale) in the United States in February 2007. In April 2013, Canada adopted the EF Scale on the Fujita scale along with 31 "Special Damage Indicators" used by the European Commission (Environment Canada) they.
Video Fujita scale
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The scale was introduced in 1971 by Tetsuya Fujita of the University of Chicago, in collaboration with Allen Pearson, head of the National Great Storms Forecasting Center/NSSFC (currently the Center for Hurricane Prediction/SPC). This scale was updated in 1973, taking into account the length and width of the account path. In the United States, beginning in 1973, tornadoes were assessed immediately after the incident. The Fujita scale was applied retroactively to tornadoes reported between 1950 and 1972 at the National Oceanic and Atmospheric Administration (NOAA) National Tornado Database. Fujita ranked tornadoes from 1916-1992 and Tom Grazulis of The Tornado Project retroactively assessed all known significant tornadoes (F2-F5 or cause death) in the US back to 1880. The Fujita scale was adopted in most areas outside the United Kingdom.
In 2007, Fujita's scale was updated, and Fujita Scale Improvement was introduced in the United States. The new scale is more accurate according to wind speed with the severity of damage caused by tornadoes.
Although each level of damage is associated with wind speed, the Fujita scale is effectively the scale of damage, and the wind speed associated with registered damage is not strictly verified. The Fujita Scale Improvement was formulated because of studies showing that the wind speed required to inflict damage by intense tornadoes on the Fujita scale is overwhelming. An expert elicitation process with top engineers and meteorologists produces wind speeds of the EF scale, however, this is biased to United States construction practice. The EF scale also improves the description of the damage parameter.
Maps Fujita scale
Derivation
The original scale derived by Fujita is a 13th-scale theoretical scale (F0-F12) designed to connect Beaufort scale and Mach number scale smoothly. F1 corresponds to the twelfth-level Beaufort scale, and F12 corresponds to the number of Mach 1.0. F0 is placed in a position that determines no damage (approximately the eighth degree of the Beaufort scale), in analogy with how the Beaufort zeroth level sets little or no wind. From these wind speed figures, qualitative descriptions of damage were made for each category of Fujita scale, and then this description was used to classify tornadoes. The diagram on the right illustrates the relationship between the Beaufort, Fujita, and Mach scales.
As Fujita scales down, little information is available on wind-induced damage, so the original scale provides slightly more than educated guesses in the wind speed range for a certain degree of damage. Fujita intends that only F0-F5 is used in practice, as it covers all possible levels of damage to skeletal homes as well as estimated estimated wind speed limits. He, however, adds a description for F6, which he describes as an "unimaginable tornado", to allow wind speeds to exceed F5 and for possible future progress in the analysis of the damage that might indicate it.
Furthermore, the original wind speed figures since found higher than the actual wind speed required to inflict damage are described in each category. Errors manifest itself to an ever increasing level when the category increases, especially in the range of F3 to F5. NOAA notes that "... precise precise wind speed numbers are actually guesses and have never been scientifically verified." Different wind speeds can cause seemingly similar damage from one place to another - even from buildings to buildings Without a thorough engineering analysis of the tornado, damage in any case, the actual wind speed required to cause such damage is unknown. "Since then, Fujita Scale Improvement has been made using better wind estimates by engineers and meteorologists.
Some sources add F levels, meaning tornadoes with winds below 39 mph, on rare occasions these weak tornadoes are observed covering a wide range of paths and lengths.
Parameters
These five categories are listed here, in order to increase the intensity.
- The rating of each given tornado is the most severe damage to any well-built skeleton house or the level of damage comparable to other damage engineering analyzes.
- Since the Fujita scale is based on the severity of the damage caused by high winds, the F6 or the F7 tornado is a theoretical construct. Structural damage can not exceed total damage, which is F5. Tornadoes with wind speeds over 319 miles per hour (513 km/h) are theoretically possible, and Bridge Creek-Moore Tornado 1999 may have been such an event. However, no such wind velocity was ever recorded and the measurement was not anywhere near the ground.
Ranking classification
For purposes such as tornado climatology studies, Fujita scale ratings can be grouped into classes.
Decommissioning in the US
The Fujita scale, introduced in 1971 as a means of distinguishing the intensity and trajectory of a tornado, assigns wind speeds to the damage that, best of all, educated guesses. Fujita and others acknowledge this immediate and intensive engineering analysis carried out through the remainder of the 1970s. This study, as well as subsequent research, shows that the tornado wind speed required to inflict the described damage is actually much lower than the F scale shown, especially for the upper category. Also, although the scale provides an overview for the type of damage that can be caused by a tornado, it gives a little leeway to the strength of the construction and other factors that may cause the building to receive higher damage at lower wind speeds. Fujita tried to address this problem somewhat in 1992 with the Modified Fujita Scale, but by that time he was semi-retired and the National Weather Service was not in a position to make updates to an entirely new scale, so most of it was not done.
In the United States, on February 1, 2007, the Fujita scale was closed to support what these scientists believed to be a more accurate Fujita Scale Improvement, replacing it. Meteorologists and engineers designing the EF Scale believe it is an increase on the F-scale in many ways - it is responsible for different degrees of damage occurring with different types of structures, both man-made and natural. The expanded and improved damage indicators and level of damage standardize what is rather ambiguous. It is also considered to provide a much better estimate for wind speed, and does not set an upper limit on wind speed for the strongest level, EF5. Some countries continue to use the original Fujita Scale. The Canadian environment has begun using the Fujita Improvement scale in Canada on April 18, 2013.
See also
References
Note
Bibliography
- Marshall, Timothy P. (2001). "Birth of Fujita Scale". Storm Track . 24 (3): 6-10.
- Edwards, Roger; J. G. LaDue; J. T. Ferree; K. Scharfenberg; C. Maier; W. L. Coulbourne (2013). "Estimated Tornado Intensity: Past, Present, and Future". Bull. Amer. Meteor. Soc . 94 (5): 641-53. Bibcode: 2013BAMS... 94..641E. doi: 10.1175/BAMS-D-11-00006.1.
External links
- Enhanced F Scale for Tornado Damage (SPC)
- Fujita Scale Improvement (EF Scale) (SPC)
- Guide to Conducting Windstorm Convection Surveys (NWS SR146)
- Tornado: Technical Oriented Perspective (NWS SR147)
- Archive of Fujita archives (Texas Tech University)
Source of the article : Wikipedia
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