Author Topic: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?  (Read 79712 times)

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Offline Jimmy Deguara

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Once again referring to Greensburg, it seems the EF-5 rating is being questioned. I won't mention by whom but it could be a due to politics be it funding requirements not sure. It is a shame if this is the case but where does one draw the line given everything is flattened and requires massive government funding to be re-built.

Anyway, what are others' thoughts about the damage they have seen. I never believed I saw any damage that matched EF-5 and was rather shocked when I heard it on the Weather Channel.

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Offline David C

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Remember that there were very few houses (or lack thereof) in Moore that represented F5 damage. It has been a while since I have looked at the Fujita scale and really have not sat down and looked at the actual 'enhancemements' (ie EF scale), although is it not the case that the most intense damage is considered (whether it is 1 well constructed house or 100)? By all accounts, the magnitude of rotation of the Greensburg storm was at the very top end of the scale -- it was a very, very intense supercell. The actual damage observed in Greensburg? -- I'll leave that to the experts (or local politicians!).
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Offline Jimmy Deguara

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Hi David,

The damage survey was also done by a reputable engineer who has done other surveys in the past including Moore. Another reputable chaser with sharp eyes for detail also suggests that the damage Moore was a somewhat more intense than in Geensburg. What readings were experienced I cannot suggest. Was it the shear size of the tornado being 1.7 miles wide as compared to half mile wide at Moore would perhaps represent different readings? Not sure.

We happen to see the damage from Moore on Tim Marshall's DVD and it was very intense in terms of the cars being toppled around and crushed. Apparently the reading may have been issued given a car was moved from its location Anyway, we will a little later - this person has to release a paper so it will be interesting professionally what evolves.

Coincidently, I went to an AMS (American Meteorological Society) meeting at Fort Worth NWS, The topic being presented was the new EF scale. The new scale in summary changes the winds speeds represented by the various damage scales. They wanted a better scale representive of the winds - the lower end were too low and the upper end winds were too high. The damage scale itself is the same so it fits with old data. There are other components whereby the steps used to determine the rating can be scrutined or checked to be more consistent but I think the summary above is sufficient for this discussion.

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Jimmy Deguara
« Last Edit: 16 May 2007, 07:14:52 PM by Jimmy Deguara »
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Jeff Brislane

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My 2c worth on the deabate about Tornado strength or intesity is this: I haven't seen real finger of God devestation since the infamous Jarrell Tornado., May 27 1997. That torndao actually scoured the ground of grass and it turned a Prime Mover into the most twisted piece of wrecked debri I have ever seen, it also stripped the skin from the carcasses of people and cows. Not to mention though that houses it destroyed were not "well constructed" brick or masonary homes, however it not only tore them completely from the foundations but it completely obliterated the debri leaving in some cases nothing at all! It was definately more savage then moore imo.

Offline David C

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Hi Jimmy,

yep I guess it does come down to a final objective assessment of the damage. Obviously there is no meaningul correlation between tornado width and strength - eg Hallam was also EF4. The thing is though, Greenburg is a two-and-a-dog hamlet - I'm not being disrespectful at all, but Moore is a fairly high-density urban area. You cannot compare the two based on apparent damage to vehicles as I would think there would be many more vehicles available as debris in an urban area. The Moore tornado was apparently 1 mile wide near Bridge Creek, just southwest of Moore. This was the other area of F5 damage. Bridge Creek is smaller than Greensburg and I dont recall seeing such obvious carnage as there was in Moore. Yes there were some cars that were twisted wrecks and buildings were completely flatened / debris removed, but in Moore there were twisted wrecks and God knows what else everywhere. So, it all comes back to the actual damage assessments in my oppinion.

yeah Jeff,  Jarrell was huge. Perhaps the somewhat slower movement of the tornado meant that anything in the path really did get dusted up. It is impossible to say whether maximum windspeeds were greater than in Moore/Bridge Creek but I agree, that on the evidence available, it does seem to have obliterated structures like no other tornado has.

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Offline David C

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Bridge Creek / Moore Tornado ( http://www.srh.noaa.gov/oun/storms/19990503/storma.php#9 )

"Bridge Creek

Two areas of F5 damage were observed in the Bridge Creek area. The first was in the Willow Lake Addition, a rural subdivision of mobile homes and some concrete slab homes in Bridge Creek, in far eastern Grady County. Two homes were completely swept from their concrete slabs, and about one dozen automobiles were carried about ¼ mile. All mobile homes in this area in the direct path of the tornado were obliterated, resulting in a high concentration of fatalities. Asphalt pavement about 1 inch thick was also peeled from a section of rural road EW125. The second area of F5 damage was observed about 1 mile west of the Grady/McClain County line and consisted of a cleanly swept slab home with foundation anchor bolts and another vehicle lofted ¼ mile. The maximum width of damage in Bridge Creek was estimated to be 1 mile. Approximately 200 mobile homes/houses were destroyed, and hundreds of other structures were damaged. The Ridgecrest Baptist Church in Bridge Creek was also destroyed. Twelve people died in Bridge Creek, nine in mobile homes. All fatalities and the majority of injuries were concentrated in the Willow Lake Addition, Southern Hills Addition, and Bridge Creek Estates, which consisted mostly of mobile homes. Compared to sections of Oklahoma and Cleveland Counties, which were also in the path of this tornado, eastern Grady County, including the Bridge Creek area, is rural and sparsely populated.

South Oklahoma City, northeast of Moore

The tornado then continued northeast and entered the southern portion of a sparsely populated industrial district. F4 damage continued through this area to near SE 89th St., the Cleveland/Oklahoma County border. Moving into Oklahoma County, the tornado curved northward, through the remaining industrial district north of Interstate 240, where 2 businesses were destroyed. This damage was rated F4. Two people were also killed at a trucking company near the intersection of S. Bryant Ave. and Interstate 240. A freight car, with an approximate weight of 18 tons, was picked up intermittently and blown ¾ mile across an open field. The body of the freight car was deposited southeast of the intersection of S. Sunnylane Rd. and SE 59th. Gouge marks were observed in the field every 50 to 100 yards, suggesting the freight car had been airborne for at least a short distance. While tornado A9 was moving through southeast Oklahoma City, another tornado (A11) touched down briefly near the intersection of SE 80th and Sooner Rd. (Oklahoma County). Tornado A9 then entered residential neighborhoods between SE 59th and SE 44th, where a woman was killed in her house.

Midwest City and the storm's demise

Tornado A9 then crossed 29th St. into Midwest City (Oklahoma County), destroying 1 building in the Boeing Complex and damaging 2 others. Widespread F3/F4 damage continued as the tornado moved across Interstate 40, affecting a large business district. Approximately 800 vehicles were damaged at Hudiburg Auto Group, located just south of Interstate 40. Hundreds of the vehicles were moved from their original location, and dozens of vehicles were picked up and tossed northward across Interstate 40 into several motels, a distance of approximately 0.2 miles. Numerous motels and other businesses including Hampton Inn, Comfort Inn, Inn Suites, Clarion Inn, Cracker Barrel, and portions of Rose State College, were destroyed. Some of the damage through this area was rated high F4, however low F5 was considered. The tornado then continued into another residential area between SE 15th and Reno Ave., where 3 fatalities occurred. High F4 damage was inflicted to 4 homes in this area. Two of these homes were located between SE 12th and SE 11th, near Buena Vista, and the other 2 homes were located on Will Rogers Rd., just south of SE 15th. Damage then diminished rapidly to F0/F1 as the tornado crossed Reno Ave. The tornado dissipated 3 blocks north of Reno Ave., between Sooner Rd. and Air Depot Blvd.

Summary

The Oklahoma State Department of Health in Oklahoma City recorded 36 direct fatalities. In addition, 5 people died of illness or accident during or shortly after the tornado, and were not considered in the direct fatality total. The number of injuries was estimated at 583, based on numbers provided from the Department of Health, which were then adjusted to account for people assumed to be unaccounted for. Injuries which resulted from removing debris, conducting search and rescue efforts, and taking shelter from the tornado, were not considered in the injury total. An estimated 1,800 homes were destroyed, and 2,500 homes were damaged, resulting in approximately $1 billion in damage."
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Offline enak_12

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This is a great picture of the Greensburg tornado for before and after comparison if you haven't all already seen it. I won't make any judgment on the EF rating.


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The majority of homes damaged/destroyed in Greensburg were built before 1980...the construction was mostly high quality....several homes that were completely destroyed were built before 1930 when hardwood was used for structural framing....I have seen several homes in the past that had been built before 1930 that were "SKINNED" by F-3 damage on the old scale (157-206 mph)but the roof and wall structures remained intact...the parameters for the new EF scale were exceeded in several areas....the quote is "...If any or all of the damage is consistant with EF-5 damage then the entire damage path is considered EF-5 damage"....Just my 2 cents....

Offline David C

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The damage scale should really reflect the wind strengths of the original work by fujita.(By which this tornado was an F4).

I'm not sure how you arrive at this conclusion John - EF5 is not based on what we see from above or in photographs, but through intensive investigation of the damage by structural engineers. There must have been some damage in Greensburg, presumably a clean foundation where a house once stood, in order for that EF5 classification to have been given in the first place. Any subsequent questioning of this must be related to the state of that house prior to the tornado,,,, or something else. In the case of the Moore tornado, there was very little F5 damage either really. That said, perhaps Moore was a more 'violent', violent tornado, it is impossible to say.


Those images above are sobering to say the least.
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Jeff Brislane

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The damage HERE at Moore was particulary severe and was classed as F5.

And here is a pic of the Moore tornado.



A quote from Sam Baricklow about the Jarrel F5 Tornado.

Quote
The amount of pavement removed by the tornado was amazing. The Jarrell tornado removed more asphalt pavement than the Dimmit, Texas tornado of June 1995.

Cars were even obliterated in Jarrel. Check out this pic.



Jarrel tornado right before it became a Barrel/Wedge



I think all three are obviously violent tornadoes, no doubt but as for ratings that has to be left for the experts. But I wonder how it compares to Andover in 1991?


« Last Edit: 17 May 2007, 03:26:37 PM by Jeff Brislane »

Offline David C

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RE: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?
« Reply #10 on: 17 May 2007, 03:43:20 PM »

Hence from damage estimates we know that we likely have a tornado in the order of F4.


What do you mean "we" John? As far as I know a NWS damage assessment rated this tornado as EF5. If there was one single point of EF5 damage then it was EF5. Unless you have been through all the damage with a fine-toothed comb you are drawing a very long bow as to be so confident that is was not. Furthermore, your comparison to Moore is no grounds on which to conclude that this tornado was not EF5 . Accordingly, and based on what Jimmy wrote initially, the question is what/if any factors may have compromised the damage assessment. If this is found to be the case the tornado will no doubt be downgraded. I certainly wont be making the call from my armchair!


Hence from damage estimates we know that we likely have a tornado in the order of F4.

Again no you do not! You have not scrutinised the damage in any detail - you are simply comparing what you see in photos to a likely high end-F5 event in an urban area (Moore). The Moore tornado swallowed up a very large car yard of course there were more mangled cars. Of course there was more debris in the funnel (i would say) to act as a wrecking ball. Nevertheless, this Greensburg storm only had to produce spots of EF5 damage to be given that rating and that seems to be the case for the moment.

When all is said and done the Fujita Scale is a damage assessment scale, not a measure of a tornado's maximum intensity. Now, given that Greensburg is but a few miles north-south and given that this tornado died just north of town it did not have a great opportunity to produce EF5 damage really. You see, this is what interests me -- how intense do these beasts get...what are the limits? I don't care what EF rating is given to this storm in fact I'd rather them all be EF1! But which storm had the more intense circulation and tornado -- both of these storms are of an intensity seldom seen.
« Last Edit: 17 May 2007, 03:50:12 PM by David Croan »
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Offline David C

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RE: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?
« Reply #11 on: 17 May 2007, 03:47:18 PM »
That tornado is a beast Jeff - I think you'll find that is how it was as it approached Bridge Creek. The funnel was more slender (lets say a large stovepipe) as it approached Moore.

What amazed me with the Andover tornado was the intensity of rotation - I guess everyone has seen the video on Tornado Video Classics. In fact that might be the tornado where they commented on suction vortices being visible.
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RE: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?
« Reply #12 on: 17 May 2007, 03:56:41 PM »
I know we are going off topic, but here is some video of the Andover tornado. This always blows me away - check out that rotation...

http://www.youtube.com/watch?v=BAmKvxIEY20

Jarrell - not the best footage  http://www.youtube.com/watch?v=k-K-bj8YhiQ

Oklahoma City -  http://www.youtube.com/watch?v=4pbqGsS5iB4&mode=related&search=

red rock Oklahoma http://www.youtube.com/watch?v=AvMMcmtNUf8
« Last Edit: 17 May 2007, 04:09:59 PM by David Croan »
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RE: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?
« Reply #13 on: 18 May 2007, 04:45:45 PM »
I agree that the Moore tornado was very likely a stronger tornado.  I havn't studied the EF scale but maybe the Greensburg tornado gets its 5 rating due to the width of the destruction. 

We passed through Greensburg area yesterday on our way south.  While we weren't permitted to enter the town we did get to the edge of town where EF4 damage started.     
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Offline Jimmy Deguara

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RE: Greensburg Tornado - EF4 or EF5 - How Savage Was It In Real Terms?
« Reply #14 on: 18 May 2007, 06:25:31 PM »
Steven,

The width of the damage path certainly was mentioned as a probable factor towards achieving EF-5 rating.

John, I don't have sufficient time to respond in depth to your points above (by the way please do not try clarifying points that should have been clarified and clearly discuss the topic).

The main aims in developing the EF-scale from the old scale was:

- to provide a scale that is consistent in terms of damage as the old scale

- to provide better estimates of wind strengths - that with better understanding of wind dynamics were proven to show lower ratings has winds too low and upper ratings had winds too high

- to provide more reliable techniques and an array of checks that enhance and hopefully provide more accurate wind estimates within the rating

So really EF-5 and F5 should be the same damage. The main point in discussion here (and hopefully to remain here) was that should funding /politics influence decisions if this was the case. To clarify even further, was the rating reasonable anyway - which is what is being discussed above? Perhaps it was close to EF-5 and pushed over the line for whatever reason?

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