Severe WX April 11th-13th, 2020 Severe Weather Threat (8 Viewers)


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436
Location
Niagara Falls, Ontario
Yeah in my personal opinion Bassfield definitely had solid EF5 potential but I'd be okay if it's left as a high-end EF4. Like Equus said, so far there is nothing that's glaringly obvious EF5 damage. Contextual evidence is borderline as well (as opposed to, say, Vilonia, Chickasha/Blanchard, or Abilene/Chapman, where the contextual damage was screaming EF5).

It's a can of worms that we should probably take to the Enhanced Fujita debate thread to open, but I really think that contextual damage, especially things like wind-rowing, tree damage, and "incredible phenomena" should absolutely count as DIs. That's just my opinion though. I'm not a wind engineer and I'm not trying to say I know more than the people who developed the scale, but not counting certain forms of damage definitely opens the floodgates for ridiculous amounts of nitpicking.
 
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vanni9283

Member
Messages
133
Location
Wayne, PA
Yeah in my personal opinion Bassfield definitely had solid EF5 potential but I'd be okay if it's left as a high-end EF4. Like Equus said, so far there is nothing that's glaringly obvious EF5 damage. Contextual evidence is borderline as well (as opposed to, say, Vilonia, Chickasha/Blanchard, or Abilene/Chapman, where the contextual damage was screaming EF5).

It's a can of worms that we should probably take to the Enhanced Fujita debate thread to open, but I really think that contextual damage, especially things like wind-rowing, tree damage, and "incredible phenomena" should absolutely count as DIs. That's just my opinion though. I'm not a wind engineer and I'm not trying to say I know more than the people who developed the scale, but not counting certain forms of damage definitely opens the floodgates for ridiculous amounts of nitpicking.
I would be in favor, however, of raising the estimated wind speeds on the scale. I'm convinced that the current wind estimates on the scale are too low. Much less the fact that numerous doppler radars recorded winds in the tornado exceeding 200 mph.
 
Messages
304
Location
Lenexa, KS
Yeah in my personal opinion Bassfield definitely had solid EF5 potential but I'd be okay if it's left as a high-end EF4. Like Equus said, so far there is nothing that's glaringly obvious EF5 damage. Contextual evidence is borderline as well (as opposed to, say, Vilonia, Chickasha/Blanchard, or Abilene/Chapman, where the contextual damage was screaming EF5).

It's a can of worms that we should probably take to the Enhanced Fujita debate thread to open, but I really think that contextual damage, especially things like wind-rowing, tree damage, and "incredible phenomena" should absolutely count as DIs. That's just my opinion though. I'm not a wind engineer and I'm not trying to say I know more than the people who developed the scale, but not counting certain forms of damage definitely opens the floodgates for ridiculous amounts of nitpicking.
I was looking at old videos of damage from the Andover, KS F5 tornado on April 26, 1991. The wind rowing of debris seems to be more impressive with the Andover tornado than the recent Bassfield/Soso, MS tornado. It is not a huge difference but is noticeable.
 

Brice

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Messages
182
Location
Virginia
I did not know that the two EF4's came from the same supercell, I thought the first supercell had one EF4 and the supercell to the south had an EF4. Turns out the second supercell had an EF3 and the northern one had 2 EF4's
 

Titan

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PerryW Project Supporter
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15
Location
Gulf Shores, AL
Hey folks! It’s been a minute since I’ve posted, but I wanted to let you guys know I was okay.

I live just outside of Collegedale/Ooltewah now, and parts of that area have been devastated by the storm. I drove through on Tuesday, and some of the damage is really close to what we saw during the 4/27/11 system. Missed my location by a couple miles at most.
 

vanni9283

Member
Messages
133
Location
Wayne, PA
Pretty legit to me!

Here's my calculations:
EF0: 69-97 mph
EF1: 98-126 mph
EF2: 127-155 mph
EF3: 155-189 mph
EF4: 190-230 mph
EF5: >230 mph
I just basically took the wind values of the current EF-scale and made them knots instead of mph. This is what their values would be as mph.
I do think the low end is a little high though.
Thinking about this again this morning, I think here's a bit more of a realistic option. I think the lower-end of the scale (winds in the EF0 and EF1 categories) are fine where they are.
Here are my revised guesses:
EF0: 65-85 mph
EF1: 86-110 mph
EF2: 111-140 mph
EF3: 141-175 mph
EF4: 176-220 mph
EF5: >220 mph
 

vanni9283

Member
Messages
133
Location
Wayne, PA
Pretty legit to me!

Here's my calculations:
EF0: 69-97 mph
EF1: 98-126 mph
EF2: 127-155 mph
EF3: 155-189 mph
EF4: 190-230 mph
EF5: >230 mph
I just basically took the wind values of the current EF-scale and made them knots instead of mph. This is what their values would be as mph.
I do think the low end is a little high though.
Thinking about it again this morning, I think here's a bit more of a realistic option. I think the lower-end of the scale (winds in the EF0 and EF1 categories are fine where they are.
Based on recorded wind speeds in tornadoes, my best guesstimate is that EF2 damage begins around 120 mph, EF3 around 150 mph, EF4 around 190-200 mph, and EF5 around 240 mph.
The person I was having this convo with thinks EF5 damage begins around 230 mph. But I do think that damage in the EF4 range can be produced by winds exceeding well over 200 mph.

The point is this....The old F-scale overestimated the wind speeds, but I think the new scale underestimates them.
 

warneagle

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Arlington, VA
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Okay, I guess only 32 of the 38 reported fatalities were tornado-related, which is still the most in any event since April 27-28, 2014.
 

Equus

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1,825
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Saragossa, AL
If the Wiki article is right we're at 17 killer tornadoes for the year, only a little past mid-April. Ten of them from this event. That's pretty scary.
 

buckeye05

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Messages
532
Location
Riverside, Ohio
Close up view of the high-end EF4 damage from the Bassfield tornado, along with construction details. This was VERY close to EF5. Note that most of the studs were straight-nailed, but it appears that a few were randomly toenailed. I wonder if they would have gone EF5 if all stud connections were tonailed?
 
Messages
304
Location
Lenexa, KS
Close up view of the high-end EF4 damage from the Bassfield tornado, along with construction details. This was VERY close to EF5. Note that most of the studs were straight-nailed, but it appears that a few were randomly toenailed. I wonder if they would have gone EF5 if all stud connections were tonailed?
That is a very informative vid. Yes, the damage looks borderline EF4/EF5.
 

Peter Griffin

Member
Messages
56
Location
Newport, NC
That is a very informative vid. Yes, the damage looks borderline EF4/EF5.
Something needs to be done with the EF scale and SOON. It is going to take Jarrell Texas level debris granulation for us to ever get an EF5 again. I feel like EF5 in this situation would have been completely justifiable. I guess I'm not an engineer but I don't think toe nailing versus straight nailing would have made any difference at all in this situation. Plenty of extreme tree damage as context. It's kinda outrageous we have got to the point where we have to have a 1 in a million chance of a tornado hitting a 'well-constructed' house at peak intensity. God forbid an anchor bolt is out of place or they didn't use the right size washer on one or it's pretty much automatic EF4.
 
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buckeye05

Member
Messages
532
Location
Riverside, Ohio
I don't really agree. Yeah, the scale is too conservative these days, and this one straddles the line a bit, but the contextual support wasn't quite there. That kind of tree damage is pretty low-end for being next to what looks like EF5 structural damage. If you want a reminder of what trees look like after an EF5, have a look at Moore or Hackleburg/Phil Campbell. No comparison. JAN also noted no grass scouring on the property, with the path only being visible in plowed dirt fields. Not what you'd expect with an EF5. Also the house remnants, while there isn't much left, are suspiciously intact and unsplintered.

With that said, this one probably was capable of producing clear cut EF5 damage. The tree damage along Willie Fortenberry Road to the northeast of Bassfield was about as intense as you can get. I think that is where the tornado likely reached its peak intensity, and if there was a well-built house in the path in that area, we would likely be looking at an EF5 rating.

In any case, the JAN survey team has regained my trust this year. They have been very meticulous and intuitive, contacted damage experts, and really took their time with this one. I trust their word.
 

Peter Griffin

Member
Messages
56
Location
Newport, NC
I don't really think because the worst tree damage wasn't co-located with the house should result in a lower rating. We all know tornadoes can fluctuate wildly in intensity at any given moment. It could have been a brief subvortice that hit the house and leveled it and might not have necessarily carried on into the trees. And my understanding is all it takes is 1 EF5 damage point. There are a lot of cases of intense tornadoes with less ground scouring than you would expect. Much like snowflakes not all tornadoes are created equal. It's just ridiculous the amount of nitpicking that goes on. WFOs are afraid to pull the trigger on borderline storms like these because they are afraid of being railroaded by the community. They need more leniency in making judgement calls on borderline storms without the worry of being lambasted for it.

But I do respect your opinion and we will just have to agree to disagree.
 

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