5 ms·

Category 1 - 74-95 mph Category 2 - 96-110 mph Category 3 - 111-129 mph Category 4 - 130-156 mph Category 5 - 157 mph or higher I’m not sure why these divi

by rblatz 3y ago

Category 1 - 74-95 mph Category 2 - 96-110 mph Category 3 - 111-129 mph Category 4 - 130-156 mph Category 5 - 157 mph or higher I’m not sure why these divisions were made. The jumps between are seemingly arbitrary, from 27 mph to 15 mph and no pattern I can discern. What makes the next jump to 192 which is the largest jump yet?

yieldcrv 3y ago
I think its the damage that benign debris can do to a person at certain speed thresholds but I could be wrong
- senectus1 3y ago
  which seems weird when you consider the building materials and styles that different regions use.
Keyframe 3y ago
Like Fujita scale for Tornados, it's about potential for potential damage it can cause which is here dependent somehow on the wind speed variable. I'm sure someone more knowledgeable about it can explain how it's correlated, but it's not about wind speeds (alone).
- lcnPylGDnU4H9OF 3y ago
  Reminded of a joke by Ron White in the context of a person choosing to remain behind in a hurricane because they believe they can withstand the wind and rain: “It’s not that the wind is blowin’, it’s what the wind is blowin’.” On topic, it makes me wonder if the wind cutoffs have to do with what can be additionally picked up by the increase in energy. I’d honestly assume not but I would still hesitate to assume that it’s arbitrary. Not really sure but the phrasing of the joke made me wonder.
  - Keyframe 3y ago
    This made me interested as well. Why the exact cut-offs, right? I found few resources like NOAA https://www.nhc.noaa.gov/pdf/sshws.pdf https://www.nhc.noaa.gov/pdf/sshws.pdf and wikipedia https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale saying basically about the wind speed that the actual wind speed is "sustained winds as average winds over a period of one minute, measured at the same 33 ft (10.1 m) height" and then I thought ok if this scalar we're using is correlated to potential damage, that would mean force, right? They did remove air pressure and storm surges as components later on. I didn't bother with air pressure outside of standard since it would deviate a lot into researching exactly that. Since it's not really my domain, I decided to wing it by googling around and looked for wind force formulas. One that I found out ( https://sites.uci.edu/energyobserver/2017/09/07/hurricane-wind-force-increases-as-the-square-of-the-velocity/#:~:text=The%20Force%20on%20a%20unit,F%20%3D%20r%20V%5E2 https://sites.uci.edu/energyobserver/2017/09/07/hurricane-wi.... ) can roughly be translated as F = v^2 but then when I charted it out with x being wind speed and y proportional force, only thing I found out was that it looked logarithmic (which I didn't need a chart for lol ). The other I found was saying for wind load formula "The generic formula for wind load is F = A x P x Cd where F is the force or wind load, A is the projected area of the object, P is the wind pressure, and Cd is the drag coefficient." I had to hunt for variables here, but gist of it is that since scale is in mph I went USA with 1 square foot for A - area (and then to square meters from that, 0,093 m^2), wind speed to m/s, and went with these (more googling): Wind Pressure (P) is P = 0.5 x p x V^2 where p (rho actually) is air density (google: 1.225 kg/m^3 at sea level and 15C, I couldn't find one at 10m height), V is our wind speed, and Cd (drag coefficient) for a flat plate which is 1.28 according to https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/shaped.html#:~:text=A%20flat%20plate%20has%20Cd,07%20to%20 https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/a.... tl;dr; I couldn't find clear cuts in Newtons. I tried minimum, maximum and average wind speeds for each categories, and then I kind of lost interest there. More googling says that it was based on established observations what wind force can do to structures, but no more than that and I couldn't source original work to see more details. Outside of optics, this is as far as my physics will lead me tonight. I'd be highly interested to see if anyone more in the know can provide methodology behind it, be it from meteorology, construction, or fluid dynamics.
- genocidicbunny 3y ago
  The thing I find interesting (in a way) is that even then, the damage caused is not a single-variate function. Where I live, we just had a massive for the area storm with really strong wind gusts. My little weather station on my balcony recorded 80mph gusts. I also have several new cracks in the walls from when the roof tried to leave the building. But in other places, hurricanes and tornadoes much stronger than that still end up leaving buildings intact. We try so hard to reduce so many things to a single number, a single qualifier. And nature just keeps showing us why that's not entirely useful. Musings from an evening spent in the dark, and perhaps the slightly spoiled leftover meatloaf that I had because there was no power to cook anything.
TylerE 3y ago
It’s an extension of the Beaufort scale. The start of class 12 aligns with the start of cat 1.
- vitus 3y ago
  That's a partial answer, but not the full story. The Beaufort scale is designed to grow as B^1.5, and so it has a natural direct extension. 13-16 on the extended Beaufort scale do not map onto category 2-5 (https://en.wikipedia.org/wiki/Beaufort_scale#Extended_scale https://en.wikipedia.org/wiki/Beaufort_scale#Extended_scale). As others mention, SSHWS was designed to reflect building damage. Apparently, Saffir's original scale only included wind speed; Simpson augmented it to include storm surge and flooding. However, the categories were at times conflicting (e.g. Hurricane Charley in 2004 was a category 4 that led to a storm surge of 7 feet, or Katrina that made landfall as a category 3 but led to a storm surge of 20+ feet in places). To reduce public confusion, the NHC simplified the scale to only use a single prescriptive factor, wind speed (oddly, while still keeping Simpson's name attached to the thing even though they removed his contribution). https://www.nps.gov/articles/saffir-simpson-hurricane-scale.htm https://www.nps.gov/articles/saffir-simpson-hurricane-scale.... contains the multi-factor scale that was discontinued in 2009.
Lendal 3y ago
They are indeed completely arbitrary, which makes "Category 6" completely meaningless/useless, just like the rest of those silly numbers. A storm with a wind speed of 130 mph is not 20% more dangerous than a storm with wind speed of 128 mph. They are equivalent dangers. It's a ridiculous system and should be abolished, but it won't, because it's good entertainment.
- Dylan16807 3y ago
  Oh come on, by that criteria you dismiss the entire concept of categories. Rounding is not a disqualifier.
- dgellow 3y ago
  Something being arbitrary doesn’t make it meaningless. It’s arbitrary and useful, so people use it.
FuriouslyAdrift 3y ago
It's supposed to be roughly correlated to damage potential to man made structures. It is also supposed to be logarithmic. https://www.nhc.noaa.gov/aboutsshws.php https://www.nhc.noaa.gov/aboutsshws.php

by rblatz 3y ago

yieldcrv 3y ago

I think its the damage that benign debris can do to a person at certain speed thresholds but I could be wrong

senectus1 3y ago
which seems weird when you consider the building materials and styles that different regions use.

Keyframe 3y ago

Like Fujita scale for Tornados, it's about potential for potential damage it can cause which is here dependent somehow on the wind speed variable. I'm sure someone more knowledgeable about it can explain how it's correlated, but it's not about wind speeds (alone).

lcnPylGDnU4H9OF 3y ago
Reminded of a joke by Ron White in the context of a person choosing to remain behind in a hurricane because they believe they can withstand the wind and rain: “It’s not that the wind is blowin’, it’s what the wind is blowin’.” On topic, it makes me wonder if the wind cutoffs have to do with what can be additionally picked up by the increase in energy. I’d honestly assume not but I would still hesitate to assume that it’s arbitrary. Not really sure but the phrasing of the joke made me wonder.
- Keyframe 3y ago
  This made me interested as well. Why the exact cut-offs, right? I found few resources like NOAA https://www.nhc.noaa.gov/pdf/sshws.pdf https://www.nhc.noaa.gov/pdf/sshws.pdf and wikipedia https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale https://en.wikipedia.org/wiki/Saffir%E2%80%93Simpson_scale saying basically about the wind speed that the actual wind speed is "sustained winds as average winds over a period of one minute, measured at the same 33 ft (10.1 m) height" and then I thought ok if this scalar we're using is correlated to potential damage, that would mean force, right? They did remove air pressure and storm surges as components later on. I didn't bother with air pressure outside of standard since it would deviate a lot into researching exactly that. Since it's not really my domain, I decided to wing it by googling around and looked for wind force formulas. One that I found out ( https://sites.uci.edu/energyobserver/2017/09/07/hurricane-wind-force-increases-as-the-square-of-the-velocity/#:~:text=The%20Force%20on%20a%20unit,F%20%3D%20r%20V%5E2 https://sites.uci.edu/energyobserver/2017/09/07/hurricane-wi.... ) can roughly be translated as F = v^2 but then when I charted it out with x being wind speed and y proportional force, only thing I found out was that it looked logarithmic (which I didn't need a chart for lol ). The other I found was saying for wind load formula "The generic formula for wind load is F = A x P x Cd where F is the force or wind load, A is the projected area of the object, P is the wind pressure, and Cd is the drag coefficient." I had to hunt for variables here, but gist of it is that since scale is in mph I went USA with 1 square foot for A - area (and then to square meters from that, 0,093 m^2), wind speed to m/s, and went with these (more googling): Wind Pressure (P) is P = 0.5 x p x V^2 where p (rho actually) is air density (google: 1.225 kg/m^3 at sea level and 15C, I couldn't find one at 10m height), V is our wind speed, and Cd (drag coefficient) for a flat plate which is 1.28 according to https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/shaped.html#:~:text=A%20flat%20plate%20has%20Cd,07%20to%20 https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/a.... tl;dr; I couldn't find clear cuts in Newtons. I tried minimum, maximum and average wind speeds for each categories, and then I kind of lost interest there. More googling says that it was based on established observations what wind force can do to structures, but no more than that and I couldn't source original work to see more details. Outside of optics, this is as far as my physics will lead me tonight. I'd be highly interested to see if anyone more in the know can provide methodology behind it, be it from meteorology, construction, or fluid dynamics.
genocidicbunny 3y ago
The thing I find interesting (in a way) is that even then, the damage caused is not a single-variate function. Where I live, we just had a massive for the area storm with really strong wind gusts. My little weather station on my balcony recorded 80mph gusts. I also have several new cracks in the walls from when the roof tried to leave the building. But in other places, hurricanes and tornadoes much stronger than that still end up leaving buildings intact. We try so hard to reduce so many things to a single number, a single qualifier. And nature just keeps showing us why that's not entirely useful. Musings from an evening spent in the dark, and perhaps the slightly spoiled leftover meatloaf that I had because there was no power to cook anything.

TylerE 3y ago

It’s an extension of the Beaufort scale. The start of class 12 aligns with the start of cat 1.

vitus 3y ago
That's a partial answer, but not the full story. The Beaufort scale is designed to grow as B^1.5, and so it has a natural direct extension. 13-16 on the extended Beaufort scale do not map onto category 2-5 (https://en.wikipedia.org/wiki/Beaufort_scale#Extended_scale https://en.wikipedia.org/wiki/Beaufort_scale#Extended_scale). As others mention, SSHWS was designed to reflect building damage. Apparently, Saffir's original scale only included wind speed; Simpson augmented it to include storm surge and flooding. However, the categories were at times conflicting (e.g. Hurricane Charley in 2004 was a category 4 that led to a storm surge of 7 feet, or Katrina that made landfall as a category 3 but led to a storm surge of 20+ feet in places). To reduce public confusion, the NHC simplified the scale to only use a single prescriptive factor, wind speed (oddly, while still keeping Simpson's name attached to the thing even though they removed his contribution). https://www.nps.gov/articles/saffir-simpson-hurricane-scale.htm https://www.nps.gov/articles/saffir-simpson-hurricane-scale.... contains the multi-factor scale that was discontinued in 2009.

Lendal 3y ago

They are indeed completely arbitrary, which makes "Category 6" completely meaningless/useless, just like the rest of those silly numbers. A storm with a wind speed of 130 mph is not 20% more dangerous than a storm with wind speed of 128 mph. They are equivalent dangers. It's a ridiculous system and should be abolished, but it won't, because it's good entertainment.

Dylan16807 3y ago
Oh come on, by that criteria you dismiss the entire concept of categories. Rounding is not a disqualifier.
dgellow 3y ago
Something being arbitrary doesn’t make it meaningless. It’s arbitrary and useful, so people use it.

FuriouslyAdrift 3y ago

It's supposed to be roughly correlated to damage potential to man made structures. It is also supposed to be logarithmic. https://www.nhc.noaa.gov/aboutsshws.php https://www.nhc.noaa.gov/aboutsshws.php