Severe WX Severe Weather Threat June 6-14

[buckeye05]

A little post-analysis of the Kouts tornado rating decision...

So the main crux of what I was saying was EF4 for Kouts was dependent on the displaced transmission tower, and a forward thinking damage survey team. Unfortunately, while I was correct in thinking that the tower would be the highest rated DI, the survey team played it very "by the book" and did not factor in the proposed updated EF scale's wind speed (170 MPH) for this type of damage to a transmission tower. Some WFO's are very forward thinking and are already factoring in the proposed updates to the scale, such as NWS Norman by utilizing root ball displacements to up the Enid tornado's wind speed estimate. Unfortunately, NWS Chicago does not seem to be particularly forward thinking, and simply went with the maximum possible wind speed for a transmission tower on the current scale, and its obvious this was the thinking based on the DAT comments. My opinion: Not a great call, and not a forward thinking rating decision, but technically correct given the current version of the EF scale. I personally would have gone 170 MPH here.

Now regarding the house, they went with 160. The DAT comments suggest that the house wasn't directly cored by the tornado, and did not suffer the full brunt of the winds within this tornado. The lackluster damage to the trees surrounding this particular home is consistent with that. The fact that the home's entire floor slid off the basement intact, combined with the fact that the house was swept away despite receiving a glancing blow from the tornado suggests that the floor was not properly attached to the basement foundation. My opinion: 160 MPH may seem a little low, but this was actually the right call given the context, obvious floor attachment issues, and glancing blow from the tornado. I might have gone with 165, but that's splitting hairs. High-end EF3 for this particular home is overall appropriate.

Overall conclusion: This tornado probably should have been rated 170 MPH EF4 based on the transmission tower, but they had plenty of basis to call it high-end EF3 given the current guidelines of the scale. Not a forward thinking call, but not unreasonable when the current transmission tower upper bound only goes to 165 MPH. An office like NWS Norman may very well have been gutsy enough to call it EF4 though. NWS Chicago decided to play it by the book however. Oh well.

 

[WeathermanLeprechaun]

A little post-analysis of the Kouts tornado rating decision...

So the main crux of what I was saying was EF4 for Kouts was dependent on the displaced transmission tower, and a forward thinking damage survey team. Unfortunately, while I was correct in thinking that the tower would be the highest rated DI, the survey team played it very "by the book" and did not factor in the proposed updated EF scale's wind speed (170 MPH) for this type of damage to a transmission tower. Some WFO's are very forward thinking and are already factoring in the proposed updates to the scale, such as NWS Norman by utilizing root ball displacements to up the Enid tornado's wind speed estimate. Unfortunately, NWS Chicago does not seem to be particularly forward thinking, and simply went with the maximum possible wind speed for a transmission tower on the current scale, and its obvious this was the thinking based on the DAT comments. My opinion: Not a great call, and not a forward thinking rating decision, but technically correct given the current version of the EF scale. I personally would have gone 170 MPH here.

Now regarding the house, they went with 160. The DAT comments suggest that the house wasn't directly cored by the tornado, and did not suffer the full brunt of the winds within this tornado. The lackluster damage to the trees surrounding this particular home is consistent with that. The fact that the home's entire floor slid off the basement intact, combined with the fact that the house was swept away despite receiving a glancing blow from the tornado suggests that the floor was not properly attached to the basement foundation. My opinion: 160 MPH may seem a little low, but this was actually the right call given the context, obvious floor attachment issues, and glancing blow from the tornado. I might have gone with 165, but that's splitting hairs. High-end EF3 for this particular home is overall appropriate.

Overall conclusion: This tornado probably should have been rated 170 MPH EF4 based on the transmission tower, but they had plenty of basis to call it high-end EF3 given the current guidelines of the scale. Not a forward thinking call, but not unreasonable when the current transmission tower upper bound only goes to 165 MPH. An office like NWS Norman may very well have been gutsy enough to call it EF4 though. NWS Chicago decided to play it by the book however. Oh well.

It does feel like they kinda alluded to this in the DAT text by going "it was the maximum windspeed estimate possible" so one of those situations like Old Kingston 2023 where the office was aware that this was probably a violent tornado but couldn't rate it as such. Difference with this one was that they easily could've/should've but played it by the rules. Wish offices were a bit more gutsy like you said and trying to find ways to actually justify tornado intensity

 

[buckeye05]

It does feel like they kinda alluded to this in the DAT text by going "it was the maximum windspeed estimate possible" so one of those situations like Old Kingston 2023 where the office was aware that this was probably a violent tornado but couldn't rate it as such. Difference with this one was that they easily could've/should've but played it by the rules. Wish offices were a bit more gutsy like you said and trying to find ways to actually justify tornado intensity

Some are, some aren't. That's the unfortunate reality. The updated scale cannot come soon enough.

Also, I just found the fatal flaw for this house that explains why the entire subfloor slid off despite the bolts. While it looked sturdy enough from aerial images, half of the foundation was modern poured concrete, while the other half was flimsy, unreinforced cinder block that completely crumbled. As the tornado impacted the house, the force of the wind pushing against the structure caused the cinder blocks to shift and collapse, which resulted in half of the foundation literally coming apart underneath the house, and subsequently caused the floor to become detached quite easily. I've said it a million times, but when the foundation itself comes apart underneath the bolts, it renders any anchoring pretty much useless. Also context wise, you can see in the last pic that the trees closest to the home lost some branches, but are still standing and aren't debarked, and actually even still have some leaves attached to the branches! This same pic also clearly shows the poured concrete portion of the foundation (left) versus the CMU portion of the foundation (right). This is also why you ABSOLUTELY NEED detailed ground level images to make rating calls. Aerial imagery simply does not show these kinds of details.

However, you can also see that trees farther away from the house are fully stubbed, fully defoliated, and suffered some debarking. This is consistent with the survey team's claim that the house was sideswiped, rather than being directly cored by the tornado. It's insane how tight the wind gradient is here, with moderate tree damage surrounding the home, and more violent looking tree damage on the same property but not immediately next to the house.

 

[WeathermanLeprechaun]

Some are, some aren't. That's the unfortunate reality. The updated scale cannot come soon enough.

Also, I just found the fatal flaw for this house that explains why the entire subfloor slid off despite the bolts. While it looked sturdy enough from aerial images, half of the foundation was modern poured concrete, while the other half was flimsy, unreinforced cinder block that completely crumbled. As the tornado impacted the house, the force of the wind pushing against the structure caused the cinder blocks to shift and collapse, which resulted in half of the foundation literally coming apart underneath the house, and subsequently caused the floor to become detached quite easily. I've said it a million times, but when the foundation itself comes apart underneath the bolts, it renders any anchoring pretty much useless. Also context wise, you can see in the last pic that the trees closest to the home lost some branches, but are still standing and aren't debarked, and actually even still have some leaves attached to the branches! This same pic also clearly shows the poured concrete portion of the foundation (left) versus the CMU portion of the foundation (right). This is also why you ABSOLUTELY NEED detailed ground level images to make rating calls. Aerial imagery simply does not show these kinds of details.

However, you can also see that trees farther away from the house are fully stubbed, fully defoliated, and suffered some debarking. This is consistent with the survey team's claim that the house was sideswiped, rather than being directly cored by the tornado. It's insane how tight the wind gradient is here, with moderate tree damage surrounding the home, and more violent looking tree damage on the same property but not immediately next to the house.

Top notch damage analysis, dude. That's why you're one of the best on here for it.

Your first point is true and unfortunate, it's probably one off the reasons the drought occurred (still can't believe we use past tense for it), but it still is a reason that inconsistencies like this happen. Not to say i have a major problem with this rating but send like some offices are scared to not follow rules and some like the E KY office with London really go thorough and find a reason to give a tornado what it deserves.

 

[buckeye05]

I would also have leaned more towards an EF4 rating for Kouts but there have been plenty tornadoes of similar strength that ended up with EF3 final ratings, which brings back the whole issue of a need for a consistent rating standard between NWS offices. Now the fact that I think it's stupid that apparently past violent tornadoes aren't going to be reexamined using the Enderlin precedent might also have to do with why I'm bringing this up.

I have heard that right now there are no changes being made to past ratings, but in the future that could change. Enderlin was so recent I wouldn't get too frustrated, and I know for a fact that there are influential people both within and outside of the NWS who want to take another look at many questionable ratings from years prior.

 

[Kds86z]

Some are, some aren't. That's the unfortunate reality. The updated scale cannot come soon enough.

Also, I just found the fatal flaw for this house that explains why the entire subfloor slid off despite the bolts. While it looked sturdy enough from aerial images, half of the foundation was modern poured concrete, while the other half was flimsy, unreinforced cinder block that completely crumbled. As the tornado impacted the house, the force of the wind pushing against the structure caused the cinder blocks to shift and collapse, which resulted in half of the foundation literally coming apart underneath the house, and subsequently caused the floor to become detached quite easily. I've said it a million times, but when the foundation itself comes apart underneath the bolts, it renders any anchoring pretty much useless. Also context wise, you can see in the last pic that the trees closest to the home lost some branches, but are still standing and aren't debarked, and actually even still have some leaves attached to the branches! This same pic also clearly shows the poured concrete portion of the foundation (left) versus the CMU portion of the foundation (right). This is also why you ABSOLUTELY NEED detailed ground level images to make rating calls. Aerial imagery simply does not show these kinds of details.

However, you can also see that trees farther away from the house are fully stubbed, fully defoliated, and suffered some debarking. This is consistent with the survey team's claim that the house was sideswiped, rather than being directly cored by the tornado. It's insane how tight the wind gradient is here, with moderate tree damage surrounding the home, and more violent looking tree damage on the same property but not immediately next to the house.

Thanks for this write up. I did see somewhere that the house wasn’t in the core of the tornado path.

 

[Kds86z]

 

[Kds86z]

Don’t think this was posted from last weds.