Enhanced Fujita Ratings Debate Thread

[Aaron Rider]

Maybe I’m wrong but weren't some of the home’s debris still on the Tylertown home slab? Specifically it wasn’t a clean sweep?

From the DAT

"....a well anchored home, was swept from the foundation, leaving debris in a pile and thrown behind the home. This home was determined to have 170 MPH EF4 damage. It is likely the tornado was at EF4 strength at other parts on the track but with only manufactured homes in rural areas impacted, this house is currently the only EF4 damage in Walthall County. The EF3 damage throughout the county was all demolished single or double wide manufactured home with the debris swept away. Widespread snapped and uprooted trees were noted on ground surveys and via drone and satellite. "

 

[joshoctober16]

Debarking is often a clear indicator of violent environment even if it cannot pin down an *exact* wind speed. If trees are fully debarked and stubbed, and if it's paired with ground scouring and structure obliteration, it still indicates violent winds. Dismissing it entirely removes a vital environmental clue.

Note: context matters!

Tree debarking will not move a rating today from EF3 → EF4 or EF4 → EF5 unless paired with high-quality structural failure evidence (or, if they're being extremely nitpicky, not at all!). So why is it even necessary to remove such an indicator?

Using “debris loading” as a blanket excuse to discard tree debarking as a violence indicator is overcorrection. It should caution surveyors to consider the cause, not dismiss the indicator entirely.

Sorry, but instead of taking things into consideration on a case by case basis, this strikes me as more unnecessary and lazy conservatism. Why are they afraid of contextual analysis?

Controlled testing and field studies have, I'm sure. shown debris can strip bark at lower winds than required for direct aerodynamic debarking. I'm sure they'll say that, and ignore how Fujita said "Extraordinary phenomena will occur" (stuff like extreme, Bridge Creek debarking)....stuff hard to explicate or replicate. But debris loading is not usually sufficient on its own to fully debark large trees around their entire circumference or create the smooth, sandblasted appearance seen in EF5 contexts. That's why I'm willing to be completely unimpressed with this change.

a other thing about the whole debark tree is only caused by debris thing ...

just cause it can happen , it doesn't mean they have to completely ignore it.

i mean what wind speed does a debris hitting a tree debark it?

cause I'm not expecting a debris moving 5 mph gently hitting the tree would just make all the bark all fall off.

even if it isn't in the EF4 range of needing wind speeds to do this , it still needs a wind speed to cause the debris to be able to debark the tree.

heck even the IF scale takes this into account.

 

[Grand Poo Bah]

Probably another few years. They’re still having to vote on certain parts of it in the different committees.

This was one of Doswell’s original criticism of the EF scale. No one really “owns it”, so an ad hoc group has to be put together across multiple fields and disciplines. I imagine the glacial pace is just due to the amount of people involved, as well as getting a large group of scientists to agree on anything.

My wild theory is it probably won't ever go into effect and we'll either switch to an entirely new system or go back to the original Fujita scale. I just think there's too many scientists at the NSSL and NOAA now who have spotted the major issues with current practices and are trying to find solutions. That is, if the NSSL isn't inexcusably shut down. Really hoping that doesn't happen.

 

[Aaron Rider]

My wild theory is it probably won't ever go into effect and we'll either switch to an entirely new system or go back to the original Fujita scale. I just think there's too many scientists at the NSSL and NOAA now who have spotted the major issues with current practices and are trying to find solutions. That is, if the NSSL isn't inexcusably shut down. Really hoping that doesn't happen.

We might have to crowd fund tornado ratings.

Which...might not be the worst.

Sorry, but I'm pretty salty about this, "all debarking is not credible as a wind speed indicator, even contextually' thing today

 

[jiharris0220]

Debarking is often a clear indicator of violent environment even if it cannot pin down an *exact* wind speed. If trees are fully debarked and stubbed, and if it's paired with ground scouring and structure obliteration, it still indicates violent winds. Dismissing it entirely removes a vital environmental clue.

Note: context matters!

Tree debarking will not move a rating today from EF3 → EF4 or EF4 → EF5 unless paired with high-quality structural failure evidence (or, if they're being extremely nitpicky, not at all!). So why is it even necessary to remove such an indicator?

Using “debris loading” as a blanket excuse to discard tree debarking as a violence indicator is overcorrection. It should caution surveyors to consider the cause, not dismiss the indicator entirely.

Sorry, but instead of taking things into consideration on a case by case basis, this strikes me as more unnecessary and lazy conservatism. Why are they afraid of contextual analysis?

Controlled testing and field studies have, I'm sure. shown debris can strip bark at lower winds than required for direct aerodynamic debarking. I'm sure they'll say that, and ignore how Fujita said "Extraordinary phenomena will occur" (stuff like extreme, Bridge Creek debarking)....stuff hard to explicate or replicate. But debris loading is not usually sufficient on its own to fully debark large trees around their entire circumference or create the smooth, sandblasted appearance seen in EF5 contexts. That's why I'm willing to be completely unimpressed with this change.

Also, the argument that debarking has occurred in ef2 tornadoes means absolutely nothing.

Because what a tornado is rated is completely at the mercy of the surveyors.

The structures they rated likely experienced ef2 winds, but that doesn’t mean the trees that were debarked also experienced those same wind velocities.

Tornadoes can change in strength very abruptly, weaker or stronger, where it had ef2 level winds in one area it can strengthen to ef4 winds in the next 100 yards.

Smithville is an excellent example of how abruptly a tornado can change strength.
The photo below, (bottom) as it entered Smithville shows how it went from causing ef0 level damage to trees to ef5 level tree damage and foot deep ground scouring in the span of less than a hundred yards.

Point is, using the “weaker” tornadoes cause debarking argument isn’t a good one, as it assumes the tornado that caused sub violent damage to a structure stayed the same intensity when it impacts foliage ahead.

 

[ColdFront]

My wild theory is it probably won't ever go into effect and we'll either switch to an entirely new system or go back to the original Fujita scale. I just think there's too many scientists at the NSSL and NOAA now who have spotted the major issues with current practices and are trying to find solutions. That is, if the NSSL isn't inexcusably shut down. Really hoping that doesn't happen.

Has it taken longer to “revise” the EF scale than it took to implement it in the first place?

I think there are still attempts by those at NOAA/NSSL to straighten out the aberrations (Tony Lyza and Alan Gerard are both on the committee) rather than just completely abandoning it and starting anew.

However, with confirmation they are removing tree debarking as a DI, as well as the decision not to factor in DOW readings, I would love to hear Lyza’s thoughts on that. Not so sure we are going to have a “better” or “marginally improved” scale post-revision after all.

 

[Grand Poo Bah]

Also, the argument that debarking has occurred in ef2 tornadoes means absolutely nothing.

Because what a tornado is rated is completely at the mercy of the surveyors.

The structures they rated likely experienced ef2 winds, but that doesn’t mean the trees that were debarked also experienced those same wind velocities.

Tornadoes can change in strength very abruptly, weaker or stronger, where it had ef2 level winds in one area it can strengthen to ef4 winds in the next 100 yards.

Smithville is an excellent example of how abruptly a tornado can change strength.
The photo below, (bottom) as it entered Smithville shows how it went from causing ef0 level damage to trees to ef5 level tree damage and foot deep ground scouring in the span of less than a hundred yards.
View attachment 44805
Point is, using the “weaker” tornadoes cause debarking is not a good argument as it assumes the tornado that caused sub violent damage to a structure stayed the same intensity when it impacts foliage.

Very good point about Smithville. Hadn't really thought about it like that before. I'm sure there are moments where even weak tornadoes can tighten up, whip across the ground, and tear stuff up. Almost like a lightning strike.

 

[joshoctober16]

Has it taken longer to “revise” the EF scale than it took to implement it in the first place?

I think there are still attempts by those at NOAA/NSSL to straighten out the aberrations (Tony Lyza and Alan Gerard are both on the committee) rather than just completely abandoning it and starting anew.

However, with confirmation they are removing trees as a DI, as well as the decision not to factor in DOW readings, I would love to hear Lyza’s thoughts on that. Not so sure we are going to have a “better” or “marginally improved” scale post-revision after all.

again they are not removing tree di , they are only removing the debarking

 

[ColdFront]

again they are not removing tree di , they are only removing the debarking

That’s what I meant. I’ll edit my comment appropriately.

 

[Grand Poo Bah]

Side note: @NickKrasz_Wx if there's any past tornadoes you want to go on a deeper dive with, the search function on this site is extremely useful, especially in the Significant Tornadoes thread. There are tons of extremely rare photos/documents in there you won't find anywhere else. This site is the best tornado archive on the internet hands down.

 

[Lake Martin EF4]

however .... Stronger then Typical resistance might not be possible anymore (sorta)

im unsure if they mean they cant put it to 205 or if they mean they cant put it to 240 (as in fully in stronger then typical resistance) however this new rule is if it isnt in the hurricane prone areas... then it at least wont get a 240 mph rating (unsure about 205-235 mph)

View attachment 44789

note ONLY ONE F5 has ever went in this hurricane prone area

After reading the list, I think the stronger than typical resistance list is not "a structure must meet ALL of the criteria to pass", but rather "a structure must meet AT LEAST ONE of the criteria to pass". If that's true, that means that for the purposes of the new EF scale all buildings located in the hurricane prone ASCE 7 area will be automatically considered to be "stronger than typical resistance".