Tornado: Use Of The Fujita Scale

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Abstract: When assessing any natural disaster, it is very common for scientists to develop uniform processes for identifying, classifying and studying these events. This uniformity in assessing a disaster is both beneficial and necessary so that as the history of these events are studied, we are able to more accurately evaluate past events and compare them to current day observations. Tornados are a natural disasters that have been recorded and studied using the Fujita Scale (F-Scale), which uses wind speed and destruction to determine the rating of the storm.

Tornados are a unique natural disaster that occurs within a cumulonimbus cloud that has drastically changed wind direction on its horizontal side. While this change in wind direction is happening in the clouds, strong winds from below are forced upward which help to turn these horizontal winds into vertical winds, allowing the funnel to form. Once the funnel forms and is stretching downward it will continue to pull warm air upwards allowing the funnel to maintain strength until the funnel reaches the ground and becomes a tornado. Since 1974, tornados have begun to be measured using the Fujita scale (F-Scale), which has created a system to more accurately compare the strength and impact of tornados.

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In lecture nineteen, Professor Fovell explains how Ted Fujita and Allen Pearson founded the Fujita scale (F-Scale) or the Fujita–Pearson scale (FPP scale) in the mid-1970s. Fujita and Pearson created this scale, where a tornado could be ranked from a category F0 that is classified as a weak storm but could be ranked as high as F5, which is considered extremely destructive. Upon the discovery and nearly worldwide acceptance of the F-Scale, scientists used this scale to go back and rate every documented tornado since 1950 so that it could be logged in the National Tornado Database ran by the National Oceanic and Atmospheric Administration (NOAA).

The original F-Scale system created assessed the storm’s category based on wind speed, path length and pathwidth but also took into consideration the amount of damage done to structures and the environment. When assessing the damage after a tornado, it was a very subjective evaluation that was based around the opinions of meteorologists and engineers after their observations, news reports and storm descriptions. Due to the subjectivity of assessing damage there have since been other versions of the F-Scale adopted, which were created to help remove biases.

As science transforms and improves its expected our techniques will too so it’s not surprising that in 2007 the original F-Scale was replaced with the Enhanced Fujita scale (EF-Scale). This enhanced version more accurately categorized a storm’s wind speed and the severity of damage but the scale still weighed more heavily on the storm’s overall damage. The EF-Scale took into account more details about the area where the tornado touched down, like the types of plants, building materials, etc.…these details are important when assessing damage because matured trees require more strength to be uprooted but once uprooted can cause much more damage then a shrub that is displaced.

One of the most noteworthy things to keep in mind is that although each tier has changed within the categories, the category system kept the same rankings of EF0 to EF5. From doing additional research Professor Fovell’s category system seem to be slightly outdated, so I will be using the EF-Scale published by the NOAAA.

EF0: Damage from a tornado that touched down outside of Philadelphia, PA in May ’19

Credit: ABC News

Earlier this year, the suburbs of Philadelphia called in reports of a tornado and upon investigation, it was determined that an EF0 tornado touched down. An EF0 tornado is categorized as a weak storm with winds reaching between 65-85 MPH, which usually indicates there was minimal damage. During a weak storm like this, it is expected to see minor damage to the surroundings like broken signs, minor building damage or uprooted trees as seen above. In our lecture, Professor Fovell says that these weak storms are the most common tornado seen and they account for almost half of all reported tornados.

EF1: Damage from a tornado that touched down outside of Indianapolis, IN in July 2018.

Credit: NOAAA, 2018

A tornado categorized as an EF1, is the second weakest storm and will cause slightly more damage then an EF0, which will be influenced by the heavier winds that are typically seen in this category because winds will range from 86-110 MPH. During this storm it is common to see broken windows, broken exterior doors on sheds or garages or roofing being ripped off. From lecture nineteen, we know that tornados that fall within the EF1-2 range, account for about 40-45% of all report tornados which makes EF1-2 the second most common types of tornados reported.

EF2: Damage from a tornado that touched down in Tampa in Oct 2019.

Credit: Kearbey, 2019

A tornado categorized as an EF2, is a storm that will cause moderate damage and appears with winds ranging from 111-135 MPH. During this EF2 storm that touched down in Tampa, they saw significant damage done to the roof of their elementary and middle school. Damage on this scale is expected and will often destroy larger trees and ruin small-detached structures like barns and mobile homes, which were all seen in Tampa after this storm.

EF3: (Left) Damage from a tornado that touched down in El Reno, OK in July 2019.

Credit: Duff, 2019

A tornado categorized as an EF3, is a storm that will cause moderate to strong damage and appears with winds ranging from 136-165 MPH. During this EF3 storm that touched down in El Reno, it is very clear that there was a lot of structural damage and displacement of materials and personal belongings. This storm was particularly impactful because El Reno suffered a very similar EF3 tornado six years ago, that was still fresh in everyone’s minds because it caused a great amount of damage and took eight lives, fortunately, this EF3 tornado did not claim any lives. Tornados that are categorized from an EF3-5 are the least common tornado typically reported, however, Professor Fovell pointed out that although the least common to see, they will on average account for 75% of all tornado related deaths.

EF4: Damage from a tornado that touched down in Linwood, Kansas 2019

Credit: Nate Chute, May 29th, 2019. Article by Allen and Hutchinson.

A tornado categorized as an EF4, is a violent storm that will cause severe amounts of damage and appears with winds ranging from 166-200 MPH. During this EF4 storm that touched down in Linwood, many parts of the town were turned into unrecognizable piles of debris. In the above picture to the left, we can see the house’s frame exposed because the siding and roofing were both ripped off. In the picture to the right, we see what looks like overturned and demolished RV, which is also almost camouflaged in the pile of debris. Throughout the city, there were multiple reports of entire houses, businesses and apartment complexes being leveled to the ground leveled.

EF5: Damage from a tornado that touched down central Oklahoma in June 2013.

Credit: (L: R) Joe Raedel, Justin Sullivan and Sarah Phipps (June 4th, 2013)

A tornado categorized as an EF5, is an extremely rare but violent storm that will cause extreme damage and appears with winds over 200 MPH. During this EF5 storm that touched down in across central Oklahoma, the second one they had seen in two weeks, the residents saw winds reach as high as 295 MPH. The storm leveled buildings of all shapes and sizes and made many more homes uninhabitable because they were still recovering from the first storm. When looking at the first two pictures above, we can see just how severely homes were destroyed due to roofs and framing being completely torn off while families’ try to sort through the rubble. In addition to the incredible damage, these devastating storms can cause they usually bring a lot of flooding with them too. In the last picture, we see a driver who is standing on top of his car to stay safe and dry. It is very likely he was not planning to be out when they storm him but due to the size and magnitude of the storm, once it started he realized the tough situation he was in.

The discovery and implementation of the F-Scale was an important milestone that helped to shape the way natural events like tornados are studied, forecasted and interpreted. Since it’s discovery over forty years ago, there have been some minor adjustments to the categories, EF0 to EF5, as we learned more about the damage created by wind and the specific role wind plays in each tier.

Bibliography:

  1. Action News: National Weather Service confirms EF0 tornado touched down at border of Bucks and Lehigh Counties Wednesday. 30 May 2019. 27 Dec. 2019. https://6abc.com/weather/tornado-hits-at-border-of-bucks-and-lehigh-counties-wednesday/5321986/
  2. Allen, Karma and Hutchinson, Bill. 29 May 2019. ABC News: Powerful EF4 tornado rips through Kansas, injures 18 and shuts down airport. 28 Dec. 2019. https://abcnews.go.com/US/kansas-declares-tornado-emergency-11-injured-airport-shut/story?id=63334787
  3. Duff, Renee. 1 July 2019. Accuweather: Deadly EF3 tornado strikes El Reno, Oklahoma, for the 2nd time in 6 years. 29 Dec. 2019. https://www.accuweather.com/en/weather-news/deadly-ef3-tornado-strikes-el-reno-oklahoma-for-the-2nd-time-in-6-years/329905
  4. Fovell G., Robert. Meteorology: An Introduction to the Wonders of the Weather (The Great Courses Series). Lecture 18: Thunderstorms, Squall Lines, and Radar. University of California, Los Angeles. 26 Dec. 2019.
  5. Fovell G., Robert. Meteorology: An Introduction to the Wonders of the Weather (The Great Courses Series). Lecture 19: Supercells, Tornadoes, and Dry Lines. University of California, Los Angeles. 26 Dec. 2019.
  6. Kearbey, Ric. 19 Oct. 2019. 10 News: Here’s what you need to know about tornadoes in Florida. 28 Dec 2019. https://www.wtsp.com/article/weather/10-tornado-facts-for-florida/67-0b783a71-705e-41be-b79a-90395e49624d
  7. (NOAAA) National Oceanic and Atmospheric Administration. NSW: National Weather Service. Enhanced Fujita Scale. 27 Dec. 2019. https://www.weather.gov/tae/ef_scale
  8. (NOAAA) National Oceanic and Atmospheric Administration. 28 July 2018. NSW: National Weather Service. EF1 Tornado Strikes Madison County. 27 Dec. 2019. Updated https://www.weather.gov/ind/EF1TornadoStrikesMadisonCounty
  9. Rice, Doyle. 4 June 2013. USA Today: Deadly Okla. tornado widest on record, rare EF5. 29 Dec. 2019. https://www.usatoday.com/story/weather/2013/06/04/okla-tornado-record-ef5/2388759/

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