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Enhanced Fujita Ratings Debate Thread (1 Viewer)

Marshal79344

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Chicago, IL
First reply in this thread in a long time, but in a discord server that I'm in, several other enthusiasts and I post damage pictures and rate the tornado based on those pictures. I feel that it would be quite fun to continue the excitement that goes on in that server over here.

All of these photos are from the same tornado:

20130515GRANBURY5.jpg 1614984157321.png
20130515GRANBURY16.jPG 20130515GRANBURY1.jpg

Some ground-level photos:
20130515GRANBURY15.jpg 20130515GRANBURY14.jpg 20130515GRANBURY6.jpg 20130515GRANBURY24.jpg 20130515GRANBURY26.jpg 20130515GRANBURY12.jpg
 
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Well, clicking on the photos to expand them reveals in the filename that they are from the EF4 Granbury, TX tornado of May 2013 (probably the most obscure violent tornado of that infamous month, edging out Shawnee).

I was going to go with EF4 anyway based on the debarking and homes destroyed down to the slab, without being able to tell from the photos if those were anchor bolts or just nails.
 

pohnpei

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shanghai
First reply in this thread in a long time, but in a discord server that I'm in, several other enthusiasts and I post damage pictures and rate the tornado based on those pictures. I feel that it would be quite fun to continue the excitement that goes on in that server over here.

All of these photos are from the same tornado:

View attachment 6391 View attachment 6390
View attachment 6392 View attachment 6389

Some ground-level photos:
View attachment 6393 View attachment 6394 View attachment 6396 View attachment 6397 View attachment 6398 View attachment 6395
There were two houses swept away anchored pretty well. But the overall contextual damage was not very impressive for a 15mph slow moving tornado. We've seen some quite slow moving F/EF5 tornados can actually largely to completely debarked All trees and mangled every single car along the path. So I will be more strict for a slow moving tornado talking about their contextual damage. Mid range EF4 was what I believe for this one.
 
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Missouri
There were two houses swept away anchored pretty well. But the overall contextual damage was not very impressive for a 15mph slow moving tornado. We've seen some quite slow moving F/EF5 tornados can actually largely to completely debarked All trees and mangled every single car along the path. So I will be more strict for a slow moving tornado talking about their contextual damage. Mid range EF4 was what I believe for this one.
I agree with the EF4 rating for Granbury; while it was a slow mover and more or less sat on top of that subdivision for several minutes it didn't go the complete devastation that Jarrell did. Plus, tornadoes like Smithville and Hackleburg were moving at 70+mph and still managed to do massive debarking of trees.
 

pohnpei

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2013 lebanon KS EF3 tornado was a quite interesting case that I think deserved to be discussed here. I don't think the EF3 rating of it was disputing because the house damage was at most low end EF3.But the incongruity between TIV's data and damage nearby was really confusing to me.
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Sean's team made a historical intercept 3 miles NNE Lebanon KS right along EE Road, Instruments on the vehicle measured peak winds somewhere around 175mph(mentioned 180mph-190mph in this link:https://en.m.wikipedia.org/wiki/List_of_tornadoes_in_the_tornado_outbreak_of_May_26–31,_2013) before destroyed by airborne debris. Extremeplanet once mentioned the instrument was destroyed when TIV2 just entered the tornado. Based on the video present here, it seems winds far exceed 200mph at the peak was very likely. Also should notice that winds of TIV2 was measured at about 3 m, which was likely lower than winds at 10m.(Video showed winds around 1 m)

Some damage around TIV2 can be found in this video:

Honestly, I don't think the tree near TIV2 was damaged at all. I just can't understand it. Why such long lasting violent wind can't even blow away leaves, let alone scour the corn field? The whole contexual damage was no way close to violent as I see but the radar was highly impressive at the time when TIV2 intercept the tornado, which lead to even more confusing about its intensity at this time. So, does anyone have any thoughts on this?

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QQ截图20210306224227.jpg
 

Equus

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Saragossa, AL
The more we get DOW data and low level measurements I'm convinced winds in high end strong/violent tornadoes are significantly underestimated by the EF scale and perhaps closer to the original F scale estimates. Either that or it's a specific combo of vertical and horizontal wind speeds necessary to cause certain damage, but honestly more than likely 200-250 mph is probably a lot more common than realized.

The original proposals for the EF scale had ideas of overlapping wind speeds for the rankings to account for such differences in speed and damage, and that could be closer; perhaps the vertical/horizontal speed ratio, forward motion, and trajectory of subvortices mean tornadoes with the same damage could be significantly different in actual intensity. Maybe. I dunno.
 
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894
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Missouri
The more we get DOW data and low level measurements I'm convinced winds in high end strong/violent tornadoes are significantly underestimated by the EF scale and perhaps closer to the original F scale estimates. Either that or it's a specific combo of vertical and horizontal wind speeds necessary to cause certain damage, but honestly more than likely 200-250 mph is probably a lot more common than realized.

The original proposals for the EF scale had ideas of overlapping wind speeds for the rankings to account for such differences in speed and damage, and that could be closer; perhaps the vertical/horizontal speed ratio, forward motion, and trajectory of subvortices mean tornadoes with the same damage could be significantly different in actual intensity. Maybe. I dunno.
I remember a study that was done around 10 years ago that demonstrated most tornadoes likely achieve at least EF2 intensity at some point in their lives even if they're on the ground for only a mile or so, the EF scale just can't measure that all the time given the way its set up (to measure damage, not wind speed) and that velocities in the most violent of tornadoes probably max out at ~350 mph or so. Stuff like Smithville, Philadelphia, Hackleburg, Joplin, Vilonia and Chapman, KS demonstrate that the EF scale significantly underestimates wind speeds in violent tornadoes. Have to find that PDF again sometime.
 

pohnpei

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I believe this is the paper you mentioned.
I remember a study that was done around 10 years ago that demonstrated most tornadoes likely achieve at least EF2 intensity at some point in their lives even if they're on the ground for only a mile or so, the EF scale just can't measure that all the time given the way its set up (to measure damage, not wind speed) and that velocities in the most violent of tornadoes probably max out at ~350 mph or so. Stuff like Smithville, Philadelphia, Hackleburg, Joplin, Vilonia and Chapman, KS demonstrate that the EF scale significantly underestimates wind speeds in violent tornadoes. Have to find that PDF again sometime.
10-03-38-038.png
 
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894
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Missouri
2013 lebanon KS EF3 tornado was a quite interesting case that I think deserved to be discussed here. I don't think the EF3 rating of it was disputing because the house damage was at most low end EF3.But the incongruity between TIV's data and damage nearby was really confusing to me.
View attachment 6427
Sean's team made a historical intercept 3 miles NNE Lebanon KS right along EE Road, Instruments on the vehicle measured peak winds somewhere around 175mph(mentioned 180mph-190mph in this link:https://en.m.wikipedia.org/wiki/List_of_tornadoes_in_the_tornado_outbreak_of_May_26–31,_2013) before destroyed by airborne debris. Extremeplanet once mentioned the instrument was destroyed when TIV2 just entered the tornado. Based on the video present here, it seems winds far exceed 200mph at the peak was very likely. Also should notice that winds of TIV2 was measured at about 3 m, which was likely lower than winds at 10m.(Video showed winds around 1 m)

Some damage around TIV2 can be found in this video:

Honestly, I don't think the tree near TIV2 was damaged at all. I just can't understand it. Why such long lasting violent wind can't even blow away leaves, let alone scour the corn field? The whole contexual damage was no way close to violent as I see but the radar was highly impressive at the time when TIV2 intercept the tornado, which lead to even more confusing about its intensity at this time. So, does anyone have any thoughts on this?

View attachment 6422 View attachment 6423 View attachment 6424 View attachment 6425 View attachment 6426
View attachment 6428
The wind speeds probably weren't as high as you think. Also, no ground scouring occurred with this tornado, in which case it seems to reasonable to believe that it probably doesn't start until winds hit the ~250 mph mark. To quote extremeplanet:

"According to past survey reports, long duration winds of EF4 intensity (166 – 200mph) are capable of causing EF5 damage, yet the vegetation around the TIV2 was largely unaffected by the bombardment of winds in excess of 175mph. Taking this into account, it is likely that ground scouring in violent tornadoes occurs due to winds significantly stronger than those encountered by the TIV2 crew."

I think the same can be said for tree debarking and vegetation stripping.
 

locomusic01

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Pennsylvania
Scouring and debarking/denuding are (at least partially) functions of debris loading. Outside of crop fields and such, you'll notice that most severe vegetation damage tends to occur in proximity to or downstream from significant debris sources. It wouldn't necessarily be surprising to see a strong or violent tornado in an open area not produce the kind of high-end vegetation damage we might otherwise expect. You'd normally see uprooted (and occasionally lofted) trees at least, but even that isn't 100% guaranteed.

Vehicle damage is kinda weird, too. For instance, this study found that significant lofting/rolling of vehicles should be common at EF4+ intensity, yet field observations show only about 15% of vehicles in the paths of such tornadoes are actually flipped or thrown. In fact, around 36% of vehicles didn't move at all. Conversely, even EF1-EF2 tornadoes can very occasionally (~4% of the time) roll or loft vehicles.

In both cases, there are probably a ton of factors at work. The structure of a tornado is incredibly complex and ever-changing, so things like vertical velocity, gust factor, pressure forces, etc. can vary enormously even over incredibly short distances and timespans.

Also, re: winds in violent tornadoes being underestimated, there are a bunch of papers out there on different approaches to simulating tornadoes. It's a fascinating subject, and several of the simulations have exceeded anything we've actually observed. For instance, depending on the swirl ratio, some of the tornadoes in this simulation produced absolutely insane velocities. In one instance, both horizontal and vertical max gusts exceeded 400 mph.

Of course, it's important to remember these are idealized simulations and they don't take into account debris loading and other important factors. They almost certainly don't reflect anything you'd actually see in reality. Still, I think it lends some credence to the idea that we may be underestimating the maximum intensity of the most violent tornadoes.
 
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Scouring and debarking/denuding are (at least partially) functions of debris loading. Outside of crop fields and such, you'll notice that most severe vegetation damage tends to occur in proximity to or downstream from significant debris sources. It wouldn't necessarily be surprising to see a strong or violent tornado in an open area not produce the kind of high-end vegetation damage we might otherwise expect. You'd normally see uprooted (and occasionally lofted) trees at least, but even that isn't 100% guaranteed.

Vehicle damage is kinda weird, too. For instance, this study found that significant lofting/rolling of vehicles should be common at EF4+ intensity, yet field observations show only about 15% of vehicles in the paths of such tornadoes are actually flipped or thrown. In fact, around 36% of vehicles didn't move at all. Conversely, even EF1-EF2 tornadoes can very occasionally (~4% of the time) roll or loft vehicles.

In both cases, there are probably a ton of factors at work. The structure of a tornado is incredibly complex and ever-changing, so things like vertical velocity, gust factor, pressure forces, etc. can vary enormously even over incredibly short distances and timespans.

Also, re: winds in violent tornadoes being underestimated, there are a bunch of papers out there on different approaches to simulating tornadoes. It's a fascinating subject, and several of the simulations have exceeded anything we've actually observed. For instance, depending on the swirl ratio, some of the tornadoes in this simulation produced absolutely insane velocities. In one instance, both horizontal and vertical max gusts exceeded 400 mph.

Of course, it's important to remember these are idealized simulations and they don't take into account debris loading and other important factors. They almost certainly don't reflect anything you'd actually see in reality. Still, I think it lends some credence to the idea that we may be underestimating the maximum intensity of the most violent tornadoes.
I remember there was a study done that speculated transonic velocities might be possible in tornadoes at extremely small scales and extremely brief moments (the area where the core meets the surface, or something like that) and thus would be almost impossible to detect. Wish I could find that PDF again.
 

locomusic01

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Yeah, that's from a paper presented at an SLS conference a number of years ago:


There's also a paper from 1986 that suggested a theoretical maximum of nearly 500 mph:


I'm skeptical of how applicable it is to real-world conditions, but it's still interesting.
 

MNTornadoGuy

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Apple Valley, MN
Scouring and debarking/denuding are (at least partially) functions of debris loading. Outside of crop fields and such, you'll notice that most severe vegetation damage tends to occur in proximity to or downstream from significant debris sources. It wouldn't necessarily be surprising to see a strong or violent tornado in an open area not produce the kind of high-end vegetation damage we might otherwise expect. You'd normally see uprooted (and occasionally lofted) trees at least, but even that isn't 100% guaranteed.

Vehicle damage is kinda weird, too. For instance, this study found that significant lofting/rolling of vehicles should be common at EF4+ intensity, yet field observations show only about 15% of vehicles in the paths of such tornadoes are actually flipped or thrown. In fact, around 36% of vehicles didn't move at all. Conversely, even EF1-EF2 tornadoes can very occasionally (~4% of the time) roll or loft vehicles.

In both cases, there are probably a ton of factors at work. The structure of a tornado is incredibly complex and ever-changing, so things like vertical velocity, gust factor, pressure forces, etc. can vary enormously even over incredibly short distances and timespans.

Also, re: winds in violent tornadoes being underestimated, there are a bunch of papers out there on different approaches to simulating tornadoes. It's a fascinating subject, and several of the simulations have exceeded anything we've actually observed. For instance, depending on the swirl ratio, some of the tornadoes in this simulation produced absolutely insane velocities. In one instance, both horizontal and vertical max gusts exceeded 400 mph.

Of course, it's important to remember these are idealized simulations and they don't take into account debris loading and other important factors. They almost certainly don't reflect anything you'd actually see in reality. Still, I think it lends some credence to the idea that we may be underestimating the maximum intensity of the most violent tornadoes.
Tornadoes like the 1987 Teton F4 hit no structures yet debarked trees and scoured the ground.
 

locomusic01

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Sure, which is why I used qualifiers like "partially" and "most" and such. That's kind of the point - there are so many variables when it comes to tornado damage that it's hard to draw conclusions from any one particular data point. The absence of severe vegetation damage doesn't necessarily preclude a violent tornado and the presence of it doesn't automatically guarantee it.
 

pohnpei

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shanghai
Scouring and debarking/denuding are (at least partially) functions of debris loading. Outside of crop fields and such, you'll notice that most severe vegetation damage tends to occur in proximity to or downstream from significant debris sources. It wouldn't necessarily be surprising to see a strong or violent tornado in an open area not produce the kind of high-end vegetation damage we might otherwise expect. You'd normally see uprooted (and occasionally lofted) trees at least, but even that isn't 100% guaranteed.

Vehicle damage is kinda weird, too. For instance, this study found that significant lofting/rolling of vehicles should be common at EF4+ intensity, yet field observations show only about 15% of vehicles in the paths of such tornadoes are actually flipped or thrown. In fact, around 36% of vehicles didn't move at all. Conversely, even EF1-EF2 tornadoes can very occasionally (~4% of the time) roll or loft vehicles.

In both cases, there are probably a ton of factors at work. The structure of a tornado is incredibly complex and ever-changing, so things like vertical velocity, gust factor, pressure forces, etc. can vary enormously even over incredibly short distances and timespans.

Also, re: winds in violent tornadoes being underestimated, there are a bunch of papers out there on different approaches to simulating tornadoes. It's a fascinating subject, and several of the simulations have exceeded anything we've actually observed. For instance, depending on the swirl ratio, some of the tornadoes in this simulation produced absolutely insane velocities. In one instance, both horizontal and vertical max gusts exceeded 400 mph.

Of course, it's important to remember these are idealized simulations and they don't take into account debris loading and other important factors. They almost certainly don't reflect anything you'd actually see in reality. Still, I think it lends some credence to the idea that we may be underestimating the maximum intensity of the most violent tornadoes.
I agree all of these ideas. The important idea is that wind is only one component of torando's strength when doing damage. Vehicle damage is indeed very comlicated. Violent rope type or stovepipe type small tornado are more prone to toss vehicle and do violent vehicle damage. Tornados like Mulvane 04, Pampa 95, Katie 16, Dalton 20, Taylor 10, Seward 01, Sibley 10 etc.. All of them had vehicle vehicle damage yet tree debarking of every single one of them was much weaker than the vehicle they made. Eile 07 was a little different because it did quite intense debarking, but it walked really slow which contribute to the level of debris loading. It was the intense pressure gredient (much smaller RMW) inside these relatively small tornados made them powerful but the actual winds don't always stronger than tornados much bigger than them.
I read this simulation paper before, very interesting thing. One thing I noticed was the ratio of horizontal and vertical winds inside tornado. Reed Timmer and his team got some Data from Linwood tornado 2019 and the ratio they have was more closer to Dr.leigh's El Reno 11 simulation which showed ratio of about 1.4(143m/s strom relative winds 99m/s vertical about 17-19m/s speed). But this was just one case so it must varied a lot in different tornados. IMHO I also believe winds well over 300mph inside the tornado was entirely possible, the hard thing was how to find it? What damage indicator can reflect these most insane winds? Especially in open field? That is a tough question but I do believe all of extremely high end damage made in very short time was a good indicator for extreme winds.
 
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Marshal79344

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Chicago, IL
Here's another one for you guys. This was probably one of the strongest January tornadoes ever recorded, striking and ripping a slash of death directly through the city of Warren, Arkansas on January 3, 1949, killing 55 people. Eyewitnesses described a multiple-vortex structure as the town was leveled. The tornado had a very long track that was documented from the air.

19490103WARREN5.jpg 19490103WARREN6.jpg 19490103WARREN7.jpg 19490103WARREN9.jpg 19490103WARREN12.PNG 19490103WARREN10.jpg 19490103WARREN3.PNG
 
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Here's another one for you guys. This was probably one of the strongest January tornadoes ever recorded, striking and ripping a slash of death directly through the city of Warren, Arkansas on January 3, 1949, killing 55 people. Eyewitnesses described a multiple-vortex structure as the town was leveled. The tornado had a very long track that was documented from the air.

View attachment 7196 View attachment 7197 View attachment 7198 View attachment 7199 View attachment 7200 View attachment 7201 View attachment 7202

Man, you beat me to posting this.

A couple more photos. This thing was well-documented.

1.jpg 2.jpg 3.jpg


This is a good resource: http://sites.rootsweb.com/~arbradle/tornado/photo_index.html
 

buckeye05

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Riverside, Ohio
Required reading for anyone who frequently visits this thread: https://www.pnas.org/content/118/14/e2021535118

Adding further support to what many already suspected. Quickest fix for this issue? Survey teams need to stop low-balling every wind speed estimate down to the lowest possible number given the damage, stop going below the lower-bound DIs for a given damage point, stop ignoring contextual evidence, and get comfortable with a liberal or at least centrist interpretation of the EF-Scale.

Bottom line, the idea that more conservative = more accurate needs to go away.
 

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