LDD 10 - Tornadoes
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South Carolina State University *
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Industrial Engineering
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Jan 9, 2024
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Uploaded by JudgeSteelHerring34
AHS 106 Natural Hazards & Human Society
Let’s Dive Deeper # 10:
Tornadoes
This assignment uses an online applet to help you understand a key concept –the Enhanced
Fujita scale. This is the tornado rating scale and is based on
observed damage, not measured
winds
.
The assumption is that the damage is related to the tornadic wind speed—something we
cannot directly measure.
Part I: Enhanced Fujita Scale for Tornado Damage
Start by opening the NOAA page with a table of tornadic wind estimates for various F scale
levels:
http://www.spc.noaa.gov/faq/tornado/ef-scale.html
.
Find the Damage Indicator table.
For each type of damage indicator, you can go to a linked details page which has a description of
the damage for each “Degree of Damage” (DOD) and a graph that shows the expected wind
speeds for that DOD.
For example, if you click on #13 you will see a table of possible visible
damage to a automobile showroom.
At DOD 3 on the table on the website for #13, there will be
broken glass in window and doors. On the graph below we can see that the expected wind speed
(EXP) for DOD 3 is approximately 87 mph, with an upper bound (UB) of 106 mph and a lower
bound (LB) of 76 mph.
Find the answers for the following questions.
1. Find the EF Scale damage indicator value for a free-standing pole.
After you click on the
correct number for that type of structure and you’re brought to the next site, what is the Degree
of Damage (DOD) if the pole is bent and what is the expected wind speed for that degree of
damage?
The degree of damage is 2 and the wind speed of that degree is around 100 mph.
2. Go back to the table with the various Fujita scales (the top of the first page).
Use the
Operational EF scale (the scale furthest on the right), what is the tornado rating (EF) based on the
wind speed for bending the free-standing pole?
That is, what is the EF rating for the wind speed
you found in the previous question (question #1)?
The tornado EF rating is 1 based on the wind speed.
3. Look at the damage page for a warehouse building.
What is the DOD and expected wind
speed if there is collapse of pre-cast concrete tilt-up panels?
The DOD is 6 and the wind speed would be around 130 mph.
4. Based on the table for Operational EF scale, what is the tornado rating (EF) based on the wind
speed for the DOD you found in the previous question (question #3)?
The tornado EF rating is 2 based on the wind speed.
Part II: Tornadoes and Flying Cows!
Now let’s use the tornado simulation. First, go to the following website:
https://cimss.ssec.wisc.edu/wxfest/Tornado/tornado.html
.This applet lets you start build a
tornado based on funnel width, wind speed, or air pressure, and then shows the impact and asks
you to determine the Enhanced Fujita scale rating.
You can refer back to the NOAA Tornado
Wind and Damage Scale pages if you want help estimating the EF values.
1. Using the default tornado settings (560 m width and 100 mph winds), what is the EF-scale
rating for the created tornado?
The EF rating for the created tornado is EF 1.
2. Now, set the wind speed to 160 mph (leave the width at 560 m).
What happens to the car?
The car gets flipped over when the wind speed is at 160 MPH.
3. Now, make the tornado as small and weak as possible.
Which of the manmade structures get
damaged?
The shingles on the house get ripped off.
4. Set the tornado to the largest size and speed.
What happens to the cow?
The cow gets sucked up by the tornado.
5. Reset the funnel width to 560 yards.
What is the
minimum
tornado wind speed (in mph)
required to completely demolish the house (that is, there aren't any parts of the house left
standing)?
The minimum speed to destroy the house is 175 MPH.
6. From your observations, which variable is the most important in generating a tornado with a
high Enhanced Fujita number?
The rotating speed is the most important.
Please remember to upload this assignment to the “LDD #10” assignment folder on D2L, being
sure you only upload a .doc, .docx, .PDF, .jpg, or .jpeg file.
Thanks!
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