Significant Severe Weather Outbreak Possible 04/26-30/2014

[Alyono]

NWS EF ratings are not meaningful EF estimates, IMO, since they refuse to use observations and radar data, which the EF scale paper states should be used.

So, the NWS ratings are not really EF ratings and technically, should not be called as such as they do not use the precise methodology from the paper. It would be like calling JMA satellite estimates Dvorak estimates, when Koba estimates would be more appropriate

[EF-5bigj]

I still wonder why they refuse to use real volicity data like at El Reno,OK. Sometimes I think they just want it to whip out everything in sight to get the EF-5 rating. TWC did a thing on the El Reno monster and called a EF-3 with winds up to 295 mph. So it appears everyone is still confused about that storms rating.

[ronyan]

NWS EF ratings are not meaningful EF estimates, IMO, since they refuse to use observations and radar data, which the EF scale paper states should be used.

So, the NWS ratings are not really EF ratings and technically, should not be called as such as they do not use the precise methodology from the paper. It would be like calling JMA satellite estimates Dvorak estimates, when Koba estimates would be more appropriate

In watching the long track Arkansas tornado on twc, there was a good time period where the radar velocities were beyond it's capability to measure, according to Forbes. Not sure what the capabilities are or whether that should be taken to mean anything as far as rating. Does this mean EF5 should be considered for that tornado or are there other factors that distort the radar?

[EF-5bigj]

So the EF scale is more guessing how powerful the tornado was not really knowing. Why do they refuse to use volicity data?

[Alyono]

So the EF scale is more guessing how powerful the tornado was not really knowing. Why do they refuse to use volicity data?

2 words, Louis Uccilini

[TropicalAnalystwx13]

The two images below are even more impressive and give me even more confidence that this was an EF5 compared to the ones I posted earlier. In the first image, you can see that what are called jersey barriers have been knocked over/rolled several feet. These don't have a lot of surface area and it's impossible for wind to get under them since they sit on the ground (and they weigh 600 pounds...), so it must have taken incredibly strong winds to do what they did.

In the second image, we see the home that the Little Rock WCM mentioned in the press conference that almost got an EF5 rating. As you can see, the home has been completely obliterated, and the debris completely removed from the site, leaving a clean foundation. In the distance, the trees are snapped off and debarked. Unlike other survey comments, the one for this house does not note subpar construction and actually notes that the house is well-constructed. If that's the case, what is preventing this from being an EF5 damage indicator?

[vbhoutex]

Not arguing here, just pointing out what I see.
Rhe foundation has obviously literally been swept clean(as with a broom which is in the picture) and even has a table and poles for a tent set up. I would like to see that picture immediately post tornado before making a judgement.
Your point on those barriers is well taken. Question there is was there any scouring in that area or did something hit those to knock them over?

[EF-5bigj]

The Louisville,MS tornado had very similar damage. Houses clean off the foundation ect. I think honestly there have been more EF-5's then the NWS cares to admit.

[TropicalAnalystwx13]

The houses that were swept off their foundations, while up to average construction, did not have anchor bolts (they used cut nails). That's why the tornado was assigned high-end EF4 and not EF5.

[EF-5bigj]

Oh I see but the Arkansas EF-4?? Swept a well built home off its foundation the moving of that concrete block thing is impressive to.

[TropicalAnalystwx13]

Oh I see but the Arkansas EF-4?? Swept a well built home off its foundation the moving of that concrete block thing is impressive to.

Sorry, I was referring to the Vilonia AR tornado. As for Louisville, NWS Jackson didn't go into too much detail about the construction of the homes swept away. In one picture though, there are a couple of trees that have only been broken off and not debarked; that would suggest to me that the structure probably wasn't incredibly sturdy. In another one, the house is obliterated but the debris remains on-site, suggesting high-end EF4.

[EF-5bigj]

So high end EF-4 damage to EF-5 with the damage Vilonia AR tornado.

[supercane4867]

Considering the area of destruction I think Vilonia tornado likely had maintained EF5 intensity at some point in its life. But does it even makes a difference by wipe out one house compare to many?
If only one house of average construction was leveled it probably would still recive a strong EF4 rating.

[Alyono]

swept clean is not a valid DI, IMO

For one major reason... the site can be contaminated by debris from other structures

[EF-5bigj]

I remember James Spann mentioning when EF-5 tornado's leave derbies it's usually from another place.

[RL3AO]

Clearly a major weakness of a damage scale is that it needs to hit something built strong enough to get a high rating. If the strongest part of a tornado doesn't hit a structure engineered strong enough to withstand 200 mph winds, then it will not be rated EF5 even if it really did have 220 mph winds.

[SouthDadeFish]

Although I know most know this, I would just like to remind people that there is little difference between high-end EF-4 damage and EF-5. The end result is catastrophic damage and those in the path of the two EF-4 twisters have nothing left. I am always amazed there aren't more deaths in situations such as these. All in all, I think the NWS did a fantastic job conveying the threat of this outbreak and surely saved many lives.

[Ntxw]

Clearly a major weakness of a damage scale is that it needs to hit something built strong enough to get a high rating. If the strongest part of a tornado doesn't hit a structure engineered strong enough to withstand 200 mph winds, then it will not be rated EF5 even if it really did have 220 mph winds.

We had this huge discussion last year on this issue with El Reno. The problem is not in the scale it is the higher up entities not willing to accept wind measurements. The EF scale is a damage scale that is only a wind estimate system. It's intended purpose isn't to measure wind but to assess destruction, damage. Until they decide to include wind measurements there is little progress that can be made.

As southdadefish said, there really is little difference to the eye between EF4 and EF5 by just scanning. Most of the damage we see in pictures of piles of debris is EF3, EF4 is sturdy structures being heavily damaged after deeper look but isn't easily seen at a glance. EF5 requires some engineering knowledge. It's very bad either way for both of these tornado's ef4 or ef5 not much difference to those folks.

[Alyono]

Clearly a major weakness of a damage scale is that it needs to hit something built strong enough to get a high rating. If the strongest part of a tornado doesn't hit a structure engineered strong enough to withstand 200 mph winds, then it will not be rated EF5 even if it really did have 220 mph winds.

We had this huge discussion last year on this issue with El Reno. The problem is not in the scale it is the higher up entities not willing to accept wind measurements. The EF scale is a damage scale that is only a wind estimate system. It's intended purpose isn't to measure wind but to assess destruction, damage. Until they decide to include wind measurements there is little progress that can be made.

As southdadefish said, there really is little difference to the eye between EF4 and EF5 by just scanning. Most of the damage we see in pictures of piles of debris is EF3, EF4 is sturdy structures being heavily damaged after deeper look but isn't easily seen at a glance. EF5 requires some engineering knowledge. It's very bad either way for both of these tornado's ef4 or ef5 not much difference to those folks.

It is NOT a damage scale. It is a wind scale where the wind estimates are based upon damage as that is usually all there is. However, in the EF scale paper, it states wind data should be used if available.

Louis Uccilini is the problem, not the EF scale

[CrazyC83]

Those pics show only snapped trees and not debarked in the area? Also was there ground scouring nearby? Without ground scouring I wouldn't go EF-5. Based on the evidence, that would be about 185 mph winds doing that damage (lower end of FR12 DI10)