Tornado Outbreak Aftermath: April 26th-30th, 2014

[Stebo]

I am a bit surprised by the lack of ef-5, it is almost getting to the point where the scale is more about building code and less about winds and damage.

[OceanStWx]

I am a bit surprised by the lack of ef-5, it is almost getting to the point where the scale is more about building code and less about winds and damage.

 

I think part of the problem is that we overestimated how strong our construction was. We're realizing it's fairly easy for an EF4 to level everything in its path.

[Stebo]

I think part of the problem is that we overestimated how strong our construction was. We're realizing it's fairly easy for an EF4 to level everything in its path.

Well there is the problem though, if an EF4 can level everything and throw it a great distance to me that should be rated higher. Case in point Tuscaloosa, the amount of destruction that occurred there back in 2011 was unimaginable yet that was an EF4.

[Ensō]

Well there is the problem though, if an EF4 can level everything and throw it a great distance to me that should be rated higher. Case in point Tuscaloosa, the amount of destruction that occurred there back in 2011 was unimaginable yet that was an EF4.

 

I disagree more strongly with this rating than I do the Tuscaloosa tornado. Although the TCL tornado caused a massive amount of intense damage and almost certainly was capable of causing EF5 (and absolutely would have been rated as such at times in the past), I don't think it caused any damage that I'd consider clear-cut EF5 when you factor in the context. In Vilonia, I thought a few areas showed what was quite clearly EF5 damage. Frankly I'd say some of the damage was comparable to the EF5-rated damage instances that we saw from the Hackleburg or Smithville tornadoes, just over a considerably smaller area.

 

I sort of agree with your first point though, and that's one of the objections I have. We've effectively changed what an EF5 tornado is, and that doesn't make sense to me from a historical standpoint.

[andyhb]

One of the main problems I have, which I'm sure has been brought up here (and has elsewhere) with skimming over the thread, is the apparent lack of attention paid to the surroundings of where the DI is analyzed. With this tornado in Vilonia, everything that you look for in an extremely violent tornado is there, unlike several other cases (especially pre-EF scale) that were given F/EF5 ratings.

[OceanStWx]

One of the main problems I have, which I'm sure has been brought up here (and has elsewhere) with skimming over the thread, is the apparent lack of attention paid to the surroundings of where the DI is analyzed. With this tornado in Vilonia, everything that you look for in an extremely violent tornado is there, unlike several other cases (especially pre-EF scale) that were given F/EF5 ratings.

 

Of course the problem is what if the surroundings weren't well built either.

 

When it comes to a 1/2 family home swept clean, you have a lower bound of 165 mph, expected of 200 mph, and upper bound of 220 mph. If you come upon this damage and find the house wasn't well anchored you have to rate it below expected (say 190 mph for example). If the neighboring houses were also poorly built and swept clean you have to rate them similarly. If they weren't swept clean, then they are rated with even lower wind speeds. Unfortunately in this case there is no way to determine if there were higher wind speeds than what was required to remove the house from the foundation.

[andyhb]

That's not what I meant. I mean things such as the shredding/debarking of low lying shrubs that occurred here and we know is associated with incredibly strong low level winds (partly based on previous cases where violent tornadoes have occurred and this didn't happen).

 

This is like the extreme corn damage caused by the Plainfield tornado in 1990 west of town to warrant its F5 rating (and rightly so).

[SouthernWx2]

I can't believe we're seeing NWS offices applying inconsistent standards to determine how much/how many instances of an X intensity damage is needed for a tornado to be classified at Y intensity. A history of past F5s shows how inconsistent the rating decision is in the case of Vilonia. The 1966 Belmond, IA, tornado was rated F5 based on only on one home, and in far more dubious circumstances (a debris pile next to the foundation, with no scouring and only minimal damage to nearby homes) than in this case, where reasonably well built/well built homes were completely swept away, ground scouring was visible (near the foundation), intense wind rowing occurred (again near the foundation), etc. Valley Mills 1973 was rated F5 because it threw two vehicles hundreds of yards, but only produced F2 building damage. Broken Bow 1982 was rated F5 based on damage to one home. Plainfield 1991 was rated F5 based on ONE patch of extreme ground scouring. Many tornadoes have been rated F3, F4, etc. based on damage at one point, so why not apply the same standard to F5 candidates? If one home was well built, especially if surrounding indicators pointed to F5, then the tornado was an F5/EF5, period.

 

Sadly, this is not the first time Little Rock has been conservative with its ratings. The Clinton tornado from Super Tuesday 2008 was in my view clearly an EF5, having left large foundations bare, trailer chassis twisted into unrecognizable shapes, two-foot-thick trees debarked and snapped off near ground level, destroyed a (steel-reinforced?) boat factory to the ground, produced ground scouring…and was rated EF4. Radar and aerial footage showed EF5 indicators that were ignored because AR just doesn't "get" F5s.

 

Anyway, so long as the NWS remains so inconsistent in its rationale for ratings (as the recent fiasco over radar measurements illustrates), then I'm no longer going to rely on the already-inaccurate NCDC/SPC database for tornado climatology. I'll just use Grazulis or my own estimates. *Rant over*

My feelings exactly.

[OceanStWx]

That's not what I meant. I mean things such as the shredding/debarking of low lying shrubs that occurred here and we know is associated with incredibly strong low level winds (partly based on previous cases where violent tornadoes have occurred and this didn't happen).

 

This is like the extreme corn damage caused by the Plainfield tornado in 1990 west of town to warrant its F5 rating (and rightly so).

 

This could be because plant damage is incredibly variable though. It's one of the major points of research with the EF scale.

[Buckeye05]

As Andy mentioned, the reason this rating is not going over well is that there are certain hallmarks that are pretty much always present in context with legitimate EF5 structural damage, and all of these hallmarks were present in Vilonia. We are talking about wind-rowed debris in huge streaks away from the foundations, scoured grass, vehicles tossed remarkable distances from where they originated, debarked shrubbery ect. For example, I know that the only homes built to EF5 standards from Phil Campbell/Hackleburg event were in the Oak Grove community. Despite this, the damage was rated EF5 in four towns due to the fact that there was overwhelming evidence of extreme intensity based on these aforementioned hallmarks that was sufficient enough to override the structural flaws. Surveyors love to use context to downgrade, but using it to upgrade seems to be a less popular idea. Still, non-traditional, non-structure related contextual evidence HAS been used to upgrade from EF4 to EF5 in the past. The question is why wasn't it used here?

[SouthernWx2]

I am a bit surprised by the lack of ef-5, it is almost getting to the point where the scale is more about building code and less about winds and damage.

 Agree 100% percent.  

[Ensō]

That's not what I meant. I mean things such as the shredding/debarking of low lying shrubs that occurred here and we know is associated with incredibly strong low level winds (partly based on previous cases where violent tornadoes have occurred and this didn't happen).

 

This is like the extreme corn damage caused by the Plainfield tornado in 1990 west of town to warrant its F5 rating (and rightly so).

 

The example I used on another forum is this. Let's say you have a few homes of average construction that have been swept away. By themselves, those homes probably only warrant a mid-range EF4 (~175-180 mph?) rating. There's no additional information to be gleaned from them other than the wind speed expected to cause the level of damage you're seeing. But now let's say the debris from those homes were scattered for hundreds of yards downstream, there's intense wind rowing and some ground scouring evident in the same area, trees and low-lying shrubs are severely damaged, vehicles were thrown and mangled, etc.

 

All of these things are often associated with EF5 tornadoes, and in fact are recommended for use in discriminating between an EF4 and EF5 rating. If all of these things are present in the same area in which homes were swept away, don't you think it's reasonable to believe that the wind speeds were most likely higher than you might normally expect given the construction quality? The fact that the construction quality of the homes by themselves may not allow you to discern EF5 damage does not mean that EF5 wind speeds weren't present, and the context surrounding those homes should be considered when making that judgment. That's what we've been getting at, and it seems to me that sometimes surveyors get so hung up on construction quality of homes that they totally overlook the surrounding context.

 

Not addressing Andy, btw. Just expanding on his point.

 

Edit - Also it looks like Buckeye ninja'd me. Anyhow, that's why we have a problem with the rating. It's not even about the slabbed homes. It's about everything surrounding those homes pointing toward EF5 intensity.

[BuffaloWeather]

Why are ratings based on damage? Do Tornadoes that do no damage still get ratings? I would tend to believe the majority of tornadoes that do occur never cause any damage as the most predominant region they hit are mainly farm lands in the central regions. Is there a way to judge the strength of Tornadoes by radar instead of ground damage? It seems to me that this would be the ideal way to efficiently rate Tornadoes. Is research not there currently, and are advancements being made to have this occur?

[OceanStWx]

The example I used on another forum is this. Let's say you have a few homes of average construction that have been swept away. By themselves, those homes probably only warrant a mid-range EF4 (~175-180 mph?) rating. There's no additional information to be gleaned from them other than the wind speed expected to cause the level of damage you're seeing. But now let's say the debris from those homes were scattered for hundreds of yards downstream, there's intense wind rowing and some ground scouring evident in the same area, trees and low-lying shrubs are severely damaged, vehicles were thrown and mangled, etc.

 

All of these things are often associated with EF5 tornadoes, and in fact are recommended for use in discriminating between an EF4 and EF5 rating. If all of these things are present in the same area in which homes were swept away, don't you think it's reasonable to believe that the wind speeds were most likely higher than you might normally expect given the construction quality? The fact that the construction quality of the homes by themselves may not allow you to discern EF5 damage does not mean that EF5 wind speeds weren't present, and the context surrounding those homes should be considered when making that judgment. That's what we've been getting at, and it seems to me that sometimes surveyors get so hung up on construction quality of homes that they totally overlook the surrounding context.

 

Not addressing Andy, btw. Just expanding on his point.

 

Edit - Also it looks like Buckeye ninja'd me. Anyhow, that's why we have a problem with the rating. It's not even about the slabbed homes. It's about everything surrounding those homes pointing toward EF5 intensity.

 

And I'm arguing that these things also don't prove that EF5 winds were present. It's their best estimate.

 

And I'm pretty sure that the residents of Vilonia don't care what the rating is.

[JasonOH]

And I'm pretty sure that the residents of Vilonia don't care what the rating is.

While they might not care, the big picture of the consistency of the whole rating system is showing itself very obviously in this instance. Like others have said, they should not only be looking at structural integrity, but also what's around it, and I feel like the survey crew may not have done this, or for some reason felt it didn't override the way the homes were built. Looking at the aerial photos, the distribution of debris near slabbed homes looks like what is usually seen in an EF-5, at least to me.

[OceanStWx]

While they might not care, the big picture of the consistency of the whole rating system is showing itself very obviously in this instance. Like others have said, they should not only be looking at structural integrity, but also what's around it, and I feel like the survey crew may not have done this, or for some reason felt it didn't override the way the homes were built. Looking at the aerial photos, the distribution of debris near slabbed homes looks like what is usually seen in an EF-5, at least to me.

 

Trust me they did.

 

Nobody rails on the consistency of the system when a survey team upgrades to the next highest rating, only when it goes the other way.

[Chicago Storm]

Nobody rails on the consistency of the system when a survey team upgrades to the next highest rating, only when it goes the other way.

Bingo.

[andyhb]

Trust me they did.

 

Nobody rails on the consistency of the system when a survey team upgrades to the next highest rating, only when it goes the other way.

 

La Plata?

[OSUmetstud]

I'm kinda interested on this whole radar estimated winds issue.  Why did the powers that be decide not to use any radar winds for classification?  If we are to be as scientific and accurate as possible, shouldn't we use all data available?  Is there some concern that using radar winds will result in a larger disparity from the original F scale?  Is there some concern that there will be a disparity in ratings between regions, as in more mobile radar on plains outbreaks vs. southeast outbreaks?

[OceanStWx]

I'm kinda interested on this whole radar estimated winds issue.  Why did the powers that be decide not to use any radar winds for classification?  If we are to be as scientific and accurate as possible, shouldn't we use all data available?  Is there some concern that using radar winds will result in a larger disparity from the original F scale?  Is there some concern that there will be a disparity in ratings between regions, as in more mobile radar on plains outbreaks vs. southeast outbreaks?

 

I really have no inside info, but I'm guessing it was just a can of worms somebody didn't want opened.

 

One of the science issues is that we just don't know exactly how to regress the sampled winds to the surface, because we don't know that much about the very near ground structure of a tornado. After all no radar can measure ground level winds.

[Ensō]

I'm kinda interested on this whole radar estimated winds issue.  Why did the powers that be decide not to use any radar winds for classification?  If we are to be as scientific and accurate as possible, shouldn't we use all data available?  Is there some concern that using radar winds will result in a larger disparity from the original F scale?  Is there some concern that there will be a disparity in ratings between regions, as in more mobile radar on plains outbreaks vs. southeast outbreaks?

 

I suspect that's probably a big part of it. I'd imagine other factors are the uncertainty regarding exactly what altitude is acceptable, how measurements at a given height level translate to near-surface winds, how near-instantaneous velocities relate to the standard 3-second gust, etc. Still, the EF-scale documentation makes it clear that remote sensing info should be used when it's deemed reliable, and I think it's a valuable tool in improving scientific accuracy.

[David Reimer]

I'm kinda interested on this whole radar estimated winds issue.  Why did the powers that be decide not to use any radar winds for classification?  If we are to be as scientific and accurate as possible, shouldn't we use all data available?  Is there some concern that using radar winds will result in a larger disparity from the original F scale?  Is there some concern that there will be a disparity in ratings between regions, as in more mobile radar on plains outbreaks vs. southeast outbreaks?

 

NOAA issued a directive last year indicating mobile weather radar data shall not be used in determining tornado strength. The El Reno tornado was rated an EF-5 based on mobile doppler radar data from OU. The official rating was downgraded to EF-3 a few months later with a few other tornadoes from May also downgraded. Ratings are expected to be based off 28 damage indicators compiled by the folks who developed the EF scale. 

 

Since the mobile weather radars were within a few kilometers of the tornado (circulation) you can bet if their data is not used to rate tornadoes NEXRAD won't be either.

[Ensō]

 

Trust me they did.

 

Nobody rails on the consistency of the system when a survey team upgrades to the next highest rating, only when it goes the other way.

 

As Andy mentioned, La Plata is pretty much the gold standard in overrating a tornado. Still, I think that's kind of a red herring. How often do survey teams assign overly generous ratings? If this were to actually occur, I'd have a problem with it. If JAN had given the Louisville, MS tornado an EF5 rating, for example, I would have strongly questioned it based on what I've seen so far. I'm sure I haven't seen the worst of the damage in that case so maybe it's not an ideal example, but I haven't yet seen anything that would indicate more than mid-range EF4. I felt the same way about Tuscaloosa. It certainly could have been rated EF5 (and would have in the past), but I don't think it was clear-cut. Same with the Washington, IL EF4 as well.

 

I don't think surveyors should just automatically assume a higher rating, and I'm pretty sure no one else does either. I don't think that's relevant to this discussion at all.

[OSUmetstud]

I really have no inside info, but I'm guessing it was just a can of worms somebody didn't want opened.

 

One of the science issues is that we just don't know exactly how to regress the sampled winds to the surface, because we don't know that much about the very near ground structure of a tornado. After all no radar can measure ground level winds.

yeah I think some sonde data from a tornado would be really cool.  I'd be interested to see how the winds change with height.  Is it like a hurricane?  Or much more complex?  

[Hoosier]

Are you talking about the large chunks of asphalt torn from Rt. 135 north of Palmyra, or is this something else? I don't recall hearing of concrete or boulders.

 

 

Yeah I think that's where it was.  Boulders was probably a bad choice of words.

[OceanStWx]

 

 

 

As Andy mentioned, La Plata is pretty much the gold standard in overrating a tornado. Still, I think that's kind of a red herring. How often do survey teams assign overly generous ratings? If this were to actually occur, I'd have a problem with it. If JAN had given the Louisville, MS tornado an EF5 rating, for example, I would have strongly questioned it based on what I've seen so far. I'm sure I haven't seen the worst of the damage in that case so maybe it's not an ideal example, but I haven't yet seen anything that would indicate more than mid-range EF4. I felt the same way about Tuscaloosa. It certainly could have been rated EF5 (and would have in the past), but I don't think it was clear-cut. Same with the Washington, IL EF4 as well.

 

I don't think surveyors should just automatically assume a higher rating, and I'm pretty sure no one else does either. I don't think that's relevant to this discussion at all.

 

 

I don't just mean EF4 to EF5 either. I mean how many times are tornadoes pushed from EF2 to EF3 or EF1 to EF2? Nobody gets up in arms about the consistency of the system then. The only reason people care is because it's the high end of the scale.

[OceanStWx]

yeah I think some sonde data from a tornado would be really cool.  I'd be interested to see how the winds change with height.  Is it like a hurricane?  Or much more complex?  

 

Given the pressure gradients over such small distances, probably much more complex. You're in the right spot for that kind of research though.

[OSUmetstud]

There was a 2 ton boulder thrown all the way to NC's outerbanks, but the survey team would not be swayed.  

[OSUmetstud]

Given the pressure gradients over such small distances, probably much more complex. You're in the right spot for that kind of research though.

Lackawanna, NY?  lol

[andyhb]

yeah I think some sonde data from a tornado would be really cool.  I'd be interested to see how the winds change with height.  Is it like a hurricane?  Or much more complex?  

 

The violent vertical motions within a tornado alone will make it much more complex than in a hurricane.