Ground Scouring

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  1. What was the average outcome for February PNA in years with a similar mean value to that of this year in December-January? Thanks!
  2. I have heard that a west-based, as opposed to east-based, Niño (so long as it remains fairly weak) tends to elongate / displace the Bermuda High farther W, meaning an elevated risk to FL. Currently, the Niño looks to be evolving on an east-based scale at first, possibly meaning a weaker high with less of an impressive risk to FL. But the CFS model, while less reliable than the ECMWF, shows a weak, central- or west-based Niño by ASO. That would mean more of a FL risk if my idea is correct. I'm skeptical this season.
  3. Even three years later, reading the accounts, and especially this book, never ceases to move me. The entire rebuilding process is like a model and a case study to be compared to those of other cities recovering after disasters. Probably the network of local businesses and the diversity of Joplin's demographics played a significant role in fostering the recovery--better than in, say, other areas that suffered comparable disasters. The bottom-up approach that worked so well in Joplin seems more plausible in a city of its size and composition than in a dense metro area like New York City.
  4. 12 NS / 4 H / 2 MH The season will overperform (in terms of total NS) relative to expectations and at least one major hurricane will hit the U.S. Otherwise the season will be a dud with no other U.S. landfalls except a TS. Edit: I would like to specify that the major landfall in the U.S. will be at least 125 kt at LF.
  5. Does anyone have ground-level images of the vegetative damage in the Bennington tornado? I would also like to hear some explanations as to why the vegetative damage was less than expected in the 2013 El Reno tornado.
  6. That lesson actually isn't even very new. Damage surveys after the April 2, 1957, Dallas F3 tornado showed that, while many of the homes were swept away, they were constructed on piers roughly eight to 12 feet "on center" (Grazulis, 1993). Even though the tornado overturned nearby railcars, the cars weren't carried a long distance and to my knowledge there was no ground scouring, so while photogrammetric estimates *possibly* suggested low-end F4 intensity, the final rating was F3 due to the poor quality of construction. Interestingly, the pier construction has long since remained in use in some Southern areas.
  7. Restaurants of the type shown here aren't usually engineered to withstand even high-end EF4 winds, so most likely it wasn't well anchored.
  8. The info comes straight from the survey: 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:
  9. 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.
  10. 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.
  11. 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.
  12. In retrospect, I definitely agree with you that, in this case, the most intense structural damage probably did not qualify for an EF5 rating for the reasons you mentioned. In reality, all the potential EF5 indicators in this case--ground scouring, lack of debris, vehicles moved long distances and mangled--were not structural in nature. Based upon the lack of clear structural EF5 damage, I will now admit that the NWS probably made the right call here. I guess that I am just a bit cynical after the fiasco with Bennington/El Reno 2013 re: radar measurements and a few other high-profile issues.
  13. It appears that the subdivision with the empty slabs was between Clover Ridge and Aspen Creek Drives just NE of downtown Vilonia. The description only mentions home destroyed (EF4) and says nothing about the ground scouring, anchoring type (if any), etc. Interestingly, homes on Cody Lane SW of Vilonia (not photographed) also were slabbed, though they were not anchored properly, and several vehicles were carried hundreds of yards in the area.
  14. You're right…I should have double-checked the available photography. I'm sorry for irritating you with my intensity estimates; I'll try to give more solid evidence from now on.
  15. At first, I suspected clean-up had taken place, but then I noticed that some of the foundations on the lower left just seemed too clean…without even debris in piles that would normally indicate clean-up work. Given the number of clean slabs, at least some of them were likely in a clean-slabbed or similar state before clean-up work had taken place. And the ground scouring is in keeping with the other Vilonia-area images I've seen.
  16. And another shot from Vilonia shows that there apparently were many more slabs than the initial photos suggested. http://www.srh.noaa.gov/lzk/imgviewer2.php?pic=aerial043014i The EF4 rating just got a lot less believable, in my view. Take a look at that ground scouring next to the slabs on the left-hand side.
  17. By the way, I've just found a new record for "most intense tree damage" I've seen--these photos posted by NWS Jackson for the Louisville, MS, EF4. Note the very clearly granulated debris as well, along with the incredible debarking of low shrubbery on a scale equal to that of El Reno-Piedmont 2011. I'm surprised this tornado's been getting overlooked.
  18. The fact that the meteorologist quoted gives no indicator as to how his source knew it was the same vehicle is a big red flag re: the reliability of the account. If the tale were true, then I would expect to see some actual documentation. As with all such cases of extremely far vehicle transport, I am taking it with a huge grain of salt and am discarding it for now.
  19. Difference of opinion is fine. I'm not basing my views on feelings, but rather what I see to be the blend of the evidence. The points have already been rehashed by others who have debated the Vilonia rating as well.
  20. I forgot to mention that the aerials showed LARGE, bare foundations with NO or VERY LITTLE debris left within hundreds of yards of the foundations. I'm also considering the weight of the evidence, such as the sustained intensity of the radar couplet near Atkins and Clinton, the shredding/twisting of the vehicles and chassis, the tree damage, etc. I'm not sure how well the steel boat factory (and the empty-slabbed structures) was constructed, but note that for a factory of its size, it didn't leave behind a lot of large debris except that which appears to have been well anchored. The remaining large debris is not very high and is mangled unrecognizably and/or severely. And many large objects near the factory appear to have been carried fairly long distances.
  21. Many surveys have ignored or not mentioned important details; for example, the Kellerville, TX (1995), survey overlooked a home that was totally swept away; the Smithville did not mention the foot-deep ground scouring outside town, documented by ExtremePlanet (2011); did not mention the complete stripping of all vegetation and topsoil from NE OK on May 5, 1960 (mentioned in Grazulis's F5-F6 booklet); etc. As for Clinton, take a good, long look at the following photographs (there are eleven pages of them) and see whether you still disagree with me. http://mike-photos.smugmug.com/gallery/4294521_qnRdX#!i=251689013&k=eAqSS You will find not only ground scouring and trailer chassis, but also those two-foot-thick trees debarked and/or snapped just above ground level; vehicles and trailers thrown long distances and mangled; low shrubs shredded/possibly debarked; the boat factory utterly flattened as were the steel factories at Wheatland and Barrie in 1985; etc. The debarking is a bit hard to see but is evident in the background of some of the images showing the boat factory. I'll admit that the scouring is not as strongly defined as in some other tornadoes, but remember, this tornado occurred in the middle of winter and in a region that has less-sandy/loose soils than in, say, OK or MS. The empty foundations came from an aerial by a Little Rock-based news outlet, but I can't find a working link to it.
  22. On another note, the outbreak continues to look more and more impressive as survey data come in. NWS Huntsville has found two EF3s in Cullman and Limestone County. Two EF1s have been found in Franklin and Mdison counties. Possible tornado tracks in Etowah and DeKalb counties are being surveyed. NWS Birmingham has found an EF3 in Russell and Lee counties, plus two EF2s and an EF1 in Jefferson County. The NWS is also surveying possible tornado tracks in Blount, Pickens, Lamar, Marion, and Fayette counties. NWS Jackson has found a long-tracked EF3 that went through Hinds-Rankin-Scott County tornadoes, in addition to the shorter-lived EF3 in Scott County. Seven EF1s have been found in Warren, Hinds, Newton, Crawford, Lowndes and Madison counties. Three EF2s hit Newton and Lowndes counties.
  23. It's quite possible, given the lack of radar and other data for most of the past few hundred years (especially before the 1970s and modern Doppler later on), that the true number of violent tornadoes is underestimated, especially for recent years on the Great Plains, given the depopulation/demise of that region's family farms since the Dust Bowl. Some studies have suggested that most tornadoes are EF2+ capable, so more violent tornadoes than are currently documented are likely to have occurred.