Enhanced Fujita Ratings Debate Thread

[joshoctober16]

a interesting thing to note for the current EF scale.

DI5 DOD7 has no wind speed for LB / EXP and UB


there was one tornado that caused this damage it was the 2014 Louisville EF4

even thought they used DI6 its clear not a single wall is standing and it seems like it was swept clean



Satellite image of the area.

 

[Central Ohio Wx]

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Do you perchance have that kmz file on hand? Would love to see it for myself.

 

[Union]

Sawyerville-Eoline, Alabama EF3 - 04/27/2011
Path Length: 72.13
Fatalities: 7
Injuries: 52

This tornado was overshadowed by others in the area. Even so, dozens of rural homes were decimated, and remarkable vegetation damage occurred. About 2 miles after forming the tornado rapidly intensified. It demolished metal buildings and twisted their steel beams, disintegrated a trailer, and tossed outbuildings and mobile homes against tree lines over 100 yards away, all while scouring the ground, shredding shrubs, and smashing apart all kinds of trees.

A small gravel road was almost completely buried under shifted forest and mud. These three images perfectly showcase the intensification of the tornado's extreme winds over time

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The tornado also tossed cars like they were toys

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The only substantial structure that took a glancing blow in this area was a well built brick home that was completely leveled.

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Plenty of mobile homes were hit though, and the increasing intensity of what was done to them paints a clear picture of how powerful this beast was.

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The tornado likely reached maximum intensity over this patch of forest where, despite lacking any real debris load, numerous large trees were completely stripped of bark, with a defined area of ground trenching right in the middle.

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The next 7.6 miles were spent entirely in unpopulated land, where the tornado weakened and then restrengthen. It entered the town of Eoline with formidable strength. The Eoline Volunteer Fire Department served as the city's storm shelter. 12 people were sheltered here when the tornado struck. "The roof just popped off 'poof' and then the bricks came swirling, the bricks were just slinging around." The station was destroyed with only two walls left standing, luckily this is where everyone was sheltering and no one was killed.

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New Rating: F4

Reasons: This one is extremely tough to rate, and I went back and forth several times. On one hand, the debarking and scouring are incredible, and cars as well as mobile/manufactured homes were turned into airborne missiles that traveled WELL over 100 meters. On the other hand, the only substantial structures that were hit collapsed in place (there were more I didn't cover). I'm choosing F4 because I'm trying to imagine what this damage looked like on ground level without the assistance of satellite imagery painting the true scale of destruction. If the goal is to stay true to historical methods, satellite imagery can't be weighted as heavily as it would need to be here to give the F5 rating.

If anyone disagrees, I'm all ears. I'll call this rating "preliminary" for now.

I wouldn't say using Sat Imagery is unrealistic, we've had it forever and it's available for some quite old tornadoes, also to a degree, plane and helicopter images aren't much different than sat and those have been used for well over a century, I still wouldn't say F5 with the inclusion of satellite just wanted to chime in

 

[Union]

Tuscaloosa, Alabama EF4 - 04/27/2011
Path length: 80.68 miles
Fatalities: 64
Injuries 1,500

This tornado has been covered extensively on this site, including the two write-ups (below) I did on it a few months ago. Tornado Talk has an 8 part summary of it, so I'll dive even deeper at a later date.





New Rating: F5

Reasons: Everything. Tossed a train car further than one has ever been tossed, snapped a 68,000 pound railroad trestle from its foundation and lifted it 100 feet uphill. Well-built structures blown away. Incredible phenomena. Significant debarking. Fujita would've undoubtedly rated this F6 if it happened in 1974 instead of 2011.

That's all of Alabama. Now onto Illinois.

Coal City-Braidwood, Illinois EF3 - 06/22/2015
Path Length: 16.26 miles
Fatalities: 0
Injuries: 7

This was one of 10 tornadoes produced by the same supercell, and the most powerful. As the tornado entered Coal City, dozens of homes were heavily damaged , and three were completely destroyed. According to the NWS summary, "Two of these homes were well built and had at least part of their structures bolted down to the foundation with bolts secure by nuts."

House 1:
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House 2 (2 stories and well built):
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House 3 (well built): Entire structure destroyed and pushed off foundation/bottom level.

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This is what surveyors called "Very high-end EF3 damage" for some reason, and is the perfect example of how we've lost the plot with tornado ratings.

New Rating: F4

Reason: Strong framed homes blown over

This being high end EF3 damage is definitely somewhat correct, this final home at least is laying on a wooden subfloor and it still being present with little other debris left means it cannot be rated as swept away, EXP DOD9 is 170mph, the other homes here also look like all walls even if they were on slabs, homes like these are commonly not even rated EF4 and Marion getting 190 was a poor survey with an entirely wrong DOD being assigned to a home wiped off it's subfloor, contextuals here also don't look that crazy which would lean into the EF4 side

 

[Aaron Rider]

This being high end EF3 damage is definitely somewhat correct, this final home at least is laying on a wooden subfloor and it still being present with little other debris left means it cannot be rated as swept away, EXP DOD9 is 170mph, the other homes here also look like all walls even if they were on slabs, homes like these are commonly not even rated EF4 and Marion getting 190 was a poor survey with an entirely wrong DOD being assigned to a home wiped off it's subfloor, contextuals here also don't look that crazy which would lean into the EF4 side

Marion was not at all a poor survey, as I've said before. I'm sorry, but I've seen people nitpicking this survey and it's honestly weenyism in reverse.

Here's the DAT for the EF4 house:


"Two story home built in 2003 at 12928 Kyler Court completely swept away with slab cleared and debris scattered into wooded area behind the home. Trees behind the homes were reduced to stubbs. Residents were not home at the time the tornado struck. Analysis by NWS damage surveyors and structural engineering experts showed that everything above the floor diaphragm of the home was removed. The studs were toe-nailed, and there was evidence of partially engineered wood being removed. The extreme tree stubbing combined with the typical construction methods of the home support an estimated peak wind speed rating of 190 mph."

Note:
Studs were toe-nailed (good)
Partially engineered wood was removed (impressive)


I don't know why they chose "typical" instead of "reasonably well-built."

They used context + damage to make a very reasonable call.

Marion was not a supremely impressive tornado but in THAT little area, it or a subvortex thereof WAS very violent.

 

[slenker]

Marion was not at all a poor survey, as I've said before. I'm sorry, but I've seen people nitpicking this survey and it's honestly weenyism in reverse.

Here's the DAT for the EF4 house:


"Two story home built in 2003 at 12928 Kyler Court completely swept away with slab cleared and debris scattered into wooded area behind the home. Trees behind the homes were reduced to stubbs. Residents were not home at the time the tornado struck. Analysis by NWS damage surveyors and structural engineering experts showed that everything above the floor diaphragm of the home was removed. The studs were toe-nailed, and there was evidence of partially engineered wood being removed. The extreme tree stubbing combined with the typical construction methods of the home support an estimated peak wind speed rating of 190 mph."

Note:
Studs were toe-nailed (good)
Partially engineered wood was removed (impressive)


I don't know why they chose "typical" instead of "reasonably well-built."

They used context + damage to make a very reasonable call.

Marion was not a supremely impressive tornado but in THAT little area, it or a subvortex thereof WAS very violent.

In further defense of this, I’ve also heard that the DAT for whatever reason didn’t mention the fact that the sill plates were indeed bolted to the foundation (unless that’s something included in the definition of “engineered wood” that I’m missing). However, I’m unsure of the full validity of this statement myself. I could be wrong.

Also, not an objective statement at all, but IMO that tornado had the look of a very violent one for sure. It had that insanely nasty debris cloud that just screamed “I’m an EF4.” Overall, I’m OK with a 190 rating here, but compared to other 190’s, it’s definitely on the weaker end.

 

[Union]

Marion was not at all a poor survey, as I've said before. I'm sorry, but I've seen people nitpicking this survey and it's honestly weenyism in reverse.

Here's the DAT for the EF4 house:


"Two story home built in 2003 at 12928 Kyler Court completely swept away with slab cleared and debris scattered into wooded area behind the home. Trees behind the homes were reduced to stubbs. Residents were not home at the time the tornado struck. Analysis by NWS damage surveyors and structural engineering experts showed that everything above the floor diaphragm of the home was removed. The studs were toe-nailed, and there was evidence of partially engineered wood being removed. The extreme tree stubbing combined with the typical construction methods of the home support an estimated peak wind speed rating of 190 mph."

Note:
Studs were toe-nailed (good)
Partially engineered wood was removed (impressive)


I don't know why they chose "typical" instead of "reasonably well-built."

They used context + damage to make a very reasonable call.

Marion was not a supremely impressive tornado but in THAT little area, it or a subvortex thereof WAS very violent.

They used the wrong DOD, that's a bad survey in my eyes, a home on a wooden subfloor shouldn't get DOD10 unless the basement is exposed and I'm pretty sure Tim Marshall was asked about this and was in agreement about the issue, If I'm remembering right some of the wooden porch in the back was even left standing, the trees behind the home aren't anything that points to high end EF4, even after being blasted by multiple houses worth of debris, homes just like this have and will continue to get EF3 ratings, EF4 is also acceptable in some cases but surveyors saying "VERY high end EF3 damage" (in relation to the EF3 mentioned in the post I quoted) may as well just be saying EF4, 165 be 166mph isn't doing much different except a different number rating. The Marion home is probably still a good 170 example for a subfloor homes but it's just not right for that home to have the same rating as the Diaz 190 DI, which is a nearly perfect 190 rating from my knowledge on the home quality.