• Member Statistics

    16,542
    Total Members
    7,904
    Most Online
    nyrangers1022
    Newest Member
    nyrangers1022
    Joined

Archived

This topic is now archived and is closed to further replies.

andyhb

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

Recommended Posts

I think there'd be a lot less argument if the EF scale was a bit more open ended with it's final rating. Currently you see reports like 'the tornado has been rated EF4 with winds between 180mph and 190mph' which is quite specific. If it was phrased such that the tornado produced upto EF4 damage with wind speeds of at least 180mph, it leaves open the fact that it was likely stronger at some point which is statistically likely as a tornado generally only spends a small part of it's life cycle impacting buildings. People might then be more happy to accept the ratings and we'd get less of these ridiculous posts that clogged up this thread when the rating was announced! Affixing an upper end to the speed based on observed damage in just a small part of the tornado life cycle seems a little odd to me.

Agreed. Stop pretending we have the type of accuracy conveyed in the ratings. We do not.

Share this post


Link to post
Share on other sites

Sorry about the rant. I have tended to be just as impressed if not more impressed by tornadoes that were rated high-end EF4 than some of the tornadoes that were rated EF5. I wish they would use other factors besides home and building damage. Like for instance the tree debarking, scouring of the ground, wind rowing, debris granulation, and mangling of vehicles have been even more impressive in high-end EF4's than even some of the more recent events rated EF5. I was just as impressed with this in Vilonia if not more impressed than even the Moore EF5 tornado from last year. The high-end EF4 rating is defenitely nothing to sneeze but there seemed to be other factors besides home/building damage that could have warranted an EF5 rating. I tend to wonder if a DOW would have helped had it been readily available.

Share this post


Link to post
Share on other sites

Sorry about the rant. I have tended to be just as impressed if not more impressed by tornadoes that were rated high-end EF4 than some of the tornadoes that were rated EF5. I wish they would use other factors besides home and building damage. Like for instance the tree debarking, scouring of the ground, wind rowing, debris granulation, and mangling of vehicles have been even more impressive in high-end EF4's than even some of the more recent events rated EF5. I was just as impressed with this in Vilonia if not more impressed than even the Moore EF5 tornado from last year. The high-end EF4 rating is defenitely nothing to sneeze but there seemed to be other factors besides home/building damage that could have warranted an EF5 rating. I tend to wonder if a DOW would have helped had it been readily available.

It all has to be used in context. Tornadoes of EF3 intensity and higher are capable of debarking trees, but if you see debarking near a home with its foundation swept clean (*and the home was well-constructed* see below), that would give more confidence in an EF5 rating. Ground scouring and granulated debris can occur in high-end EF4 tornadoes.

 

The image of the neighborhood in Vilonia was high-end EF4 damage. Despite foundations swept clean and what appears to be some ground scouring near the homes, the structures lacked anchor bolts and instead used cut nails. EF4 tornadoes are able to sweep homes with this construction away. 

Share this post


Link to post
Share on other sites

According to various sources, including Harold Brooks, the door itself wasn't properly engineered.

Share this post


Link to post
Share on other sites

Anyone have the damage assessment for the Lincoln County, TN tornado or have I overlooked it?

Share this post


Link to post
Share on other sites

According to various sources, including Harold Brooks, the door itself wasn't properly engineered.

 

Do you have more information on this? I only found two other articles and they didn't provide a lot of details other than it looks like the shelter sustained an impact between the 'deadbolt' and the doorhandle. It also looks like the door was a 'swing in' type of construction.

Share this post


Link to post
Share on other sites

The only problem with the article is 1) that it says most (not ALL!) homes that were leveled lacked anchor bolts, implying that some did; and 2) that at least one home on E Wicker Street, just northeast of downtown Vilonia, was apparently anchor-bolted and yet completely swept away, with substantial ground scouring and removal of vegetation next to the foundation. Maybe the surveyors missed the signs of anchorage? Needless to say, the EF4 rating looks much more questionable than it did a week ago.

Share this post


Link to post
Share on other sites

The only problem with the article is 1) that it says most (not ALL!) homes that were leveled lacked anchor bolts, implying that some did; and 2) that at least one home on E Wicker Street, just northeast of downtown Vilonia, was apparently anchor-bolted and yet completely swept away, with substantial ground scouring and removal of vegetation next to the foundation. Maybe the surveyors missed the signs of anchorage? Needless to say, the EF4 rating looks much more questionable than it did a week ago.

 

While some homes were anchor-bolted I bet the spacing for the anchor bolts was about 1 cm too far apart.

 

Or maybe some washers had a diameter 0.5 cm less than what is needed for an EF5 rating, cuz, you know.

Share this post


Link to post
Share on other sites

Hmm...

 

Rg7omG7.jpg

This line says a lot about the survey's reasoning: "Additional structure strengthening mechanisms were unknown at time of survey." Clearly regional construction analysis played a big role in the decision not to upgrade despite what appears to be clear EF5 evidence.

Share this post


Link to post
Share on other sites

This line says a lot about the survey's reasoning: "Additional structure strengthening mechanisms were unknown at time of survey." Clearly regional construction analysis played a big role in the decision not to upgrade despite what appears to be clear EF5 evidence.

 

The thing is that it says right there "destruction of engineered and/or well constructed residence; slab swept clean", with proper anchoring to the foundation/base plate. If it was unknown at the time of the survey (which seems like a very poor reason for not adjusting the rating), does this all the sudden mean the tornado can't be retroactively raised to an EF5? It happened with Rainsville in 2011.

Share this post


Link to post
Share on other sites

I see this was added to the LZK page, interpret it how you wish.

 

To be fair, not every clean slab that was checked along the track of the tornado had cut nails. Several of these slabs had anchor bolts. However, there were signs that some of the bolts were improperly installed. At one home, for instance, there were no washers or nuts found on the bolts, and the bolts were not sheared off. In general, if survey crews found anchor bolts, and they were used as intended, the slabs were not clean.

Share this post


Link to post
Share on other sites

Nothing will convince me otherwise. This tornado deserved an EF5 rating and like I said no one will convince me otherwise. Heck even the Washington Illinois tornado last fall was a good candidate for an EF5 rating. Oh but EF5's don't happen in November or in Arkansas. Other factors in some tornadoes despite construction of homes that were rated high-end EF4 have been even more impressive than some recent EF5 tornadoes. That picture above seals the deal for an EF5 rating. There is more than an argument.

Share this post


Link to post
Share on other sites

Nothing will convince me otherwise. This tornado deserved an EF5 rating and like I said no one will convince me otherwise. Heck even the Washington Illinois tornado last fall was a good candidate for an EF5 rating. Oh but EF5's don't happen in November or in Arkansas. Other factors in some tornadoes despite construction of homes that were rated high-end EF4 have been even more impressive than some recent EF5 tornadoes. That picture above seals the deal for an EF5 rating. There is more than an argument.

 

I don't really have a problem with the Washington, IL EF4 (though it may well have been rated F5 in the past), but I think this case is quite clear. As someone mentioned earlier in this thread, it's quite clear that the EF-scale, at least as it relates to high-end tornadoes, is no longer an assessment of intensity/damage/wind speed. It's an assessment of construction quality, and that's something entirely different and not particularly relevant to assessing tornado intensity. And it's even more clear that the rating a tornado receives depends heavily on where it occurs and the people who survey it.

Share this post


Link to post
Share on other sites

^The homes in Washington, IL were swept off of their floor joists/subfloors, not their foundations. It was visually impressive, but there is a big difference there. But I agree that the E Wicker St home in Vilonia is the final nail in the coffin for any remaining doubt about 200MPH+ winds at that location.

Share this post


Link to post
Share on other sites

The NWS Little Rock makes their case rest upon the fact that the well-built homes supposedly had debris left on their foundations immediately after the storm. Well, LZK should tell that to Tim Marshall et al. who found that several of the homes in Moore after 05/20/2013 had their bare slabs partially covered by debris from other destroyed structures. Thus, the mere presence of debris on the foundation is not necessarily due to/from/related to the home itself, but may have come from other structures, thus proving that debris does not mean the damage was not EF5 in intensity.

Share this post


Link to post
Share on other sites

What site did you get that picture from?

It's from the LZK survey map. Home pictured is the one marked EF4 along E Wicker St in Vilonia.

http://www.srh.noaa.gov/images/lzk/gis/tor042714a.kml

 

The NWS Little Rock makes their case rest upon the fact that the well-built homes supposedly had debris left on their foundations immediately after the storm. Well, LZK should tell that to Tim Marshall et al. who found that several of the homes in Moore after 05/20/2013 had their bare slabs partially covered by debris from other destroyed structures. Thus, the mere presence of debris on the foundation is not necessarily due to/from/related to the home itself, but may have come from other structures, thus proving that debris does not mean the damage was not EF5 in intensity.

I didn't see anything about that. Where does it say that debris covering the foundations came into play? LZK lists the main home in question as "slab swept clean".

Share this post


Link to post
Share on other sites

Yeah I was mainly referring to the Vilonia tornado. Who actually did this survey? What I mean who assisted NWS in Little Rock with this survey?

 

Someone from TSA came in to assist whoever at LZK did the surveys, I didn't catch who though.

Share this post


Link to post
Share on other sites

It worked for me when I clicked on the damage point. The pic doesn't load in the pop-up window but it still shows up if you click to enlarge it.

Share this post


Link to post
Share on other sites

This event, like everything else, should get a final review before it becomes official in about 3 months.  Perhaps we will see a change in the rating but I wouldn't hold my breath.

Share this post


Link to post
Share on other sites

It's from the LZK survey map. Home pictured is the one marked EF4 along E Wicker St in Vilonia.

http://www.srh.noaa.gov/images/lzk/gis/tor042714a.kml

I didn't see anything about that. Where does it say that debris covering the foundations came into play? LZK lists the main home in question as "slab swept clean". 

The info comes straight from the survey:

To be fair, not every clean slab that was checked along the track of the tornado had cut nails. Several of these slabs had anchor bolts. However, there were signs that some of the bolts were improperly installed. At one home, for instance, there were no washers or nuts found on the bolts, and the bolts were not sheared off. In general, if survey crews found anchor bolts, and they were used as intended, the slabs were not clean. 

http://www.srh.noaa.gov/lzk/?n=anchor0514.htm

 

And then there's this image showing a large, brick-built, newer-looking building (a bank?) that was completely leveled and not even listed as a damage point by LZK:

 

SzydMGj.jpg

Share this post


Link to post
Share on other sites

  • Recently Browsing   0 members

    No registered users viewing this page.