Australian Severe Weather Forum

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.

Regards,

Jimmy Deguara

I must say Jimmy, when i first saw the damage my feel was EF4 or thereabouts:the town was leveled no question, but i didnt see what you normally characterise to be the truly devastating effects of F5: Debris mainly remained over houses(in an F5 generally all you see are foundations and very small pieces of debris, basically shredded(this is from statements by Fujita, and damage from Tornadoes such as that at Moore)), and were of a larger size that what would be expected. Furthermore on appearances, not all the well constructed houses were destroyed and razed as you would expect from an F5. The wind speed is also more suited to an F4 top of the range.

I too was relatively suprised when i saw the statement of EF5, but didnt question it given the supposedly reputed authorities issuing it. Additionally, many people survived within structures, again not a characteristic youd expect in an F5: generally speaking F5 damage is in conjunction with a number of deaths of people not protected in a shelter, as even the most well constructed houses are blown away.

Some additional notes:
Many trees not stripped and heavily damaged as would be expected.
Cars dont look as mangled or like being thrown for long distances as was seen in Moore Oklahoma and other F5s, rather displaced.
Debris from singular houses often remains over the housing site.
Many brick structures heavily damaged, but not destroyed.
Maximum winds were estimated at 205 mph. This is not consistent with F5 expectations, rather in Fujita's original work this is borderline F4(strictly speaking F3)
Looking further into the EF scale, the damage visible in fact indicates EF3(walls collapse in brick structures) to EF4(brick structures knocked down), rather than the suggested EF5, which would imply brick structures blown away(or translocated).

The pieces of the puzzle dont add up, and while an observational system of tornado strength measurement is used i guess we will never know how powerful the tornado actually was.

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!).

I think the problem here is that the media are only showing the worst damage seen: and if this is the case then I cannot understand how this tornado was rated EF5: there is no trace of well built buildings being blown away, nor even full collapse of brick buildings. While tornadoes can be fickle in their damage paths I severely doubt that EF5 damage would be rated without some clear indications of blown away strong structures to justify the analysis. If the windspeed was only 205mph then I doubt such evidence would be present, and thus I could conclude that monetary factors may have a part to play in the analysis.Clearly if It was an EF5 it was only an isolated vortex within its body and the media hasnt seen the damage assessed justifiying it, as the majority of images from the town skew towards EF4/EF3.

Maybe I'm wrong, but while such rotation and an intense supercell were occuring a tornado formed: and while it may have been a strong tornado, from the wind speed inferred the signature was not fully conductive to the ground it seems. And hence I dont believe it warrants the EF5 rating purely on the basis of windspeed being unlikely to generate sufficient damage.

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.

Regards,

Jimmy Deguara

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.

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.

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."

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.

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....

In reference to the image posted by enak: i would very much like to see an image of the roadway two streets to the left of the main N-S street. It looks quite possible at that location that we have asphalt ripped up(at least partially) and if that is the case It would be there that i would be looking for some tracer of EF5 damage.

Just with respect to well built houses(pre 1980 id assume from the design): images shown of the town shown several of these still intact. I have heard no statement or report mention a particular reason why EF5 was assessed: Whereas for the Moore tornado there was significant evidence in all cases to warrant the damage assessment.

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.

Well david the fujita scale is derived from the windspeed as a proportion of the mach number in the F-series. Fujita defined the various categories based on the damage caused by a wind speed of that magnitude, as can be seen in the diagram of his work below, and was originally designed to pick up categorising of wind speeds where the beaufort scale left off.

http://www.spc.noaa.gov/efscale/Fujita1002.jpg

As can be seen there were 6 categories divised, which include descriptions(referenced from NWS.noaa.gov)

F0 (Gale) < 73MPH Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.
F1 (Weak) 73-112MPH Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads.
F2 (Strong)113-157MPH Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.
F3 (Severe) 158-206MPH Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.
F4 (Devastating)207-260MPH Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated.
F5 (Incredible) 261-318MPH Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yds); trees debarked; incredible phenomena will occur.

Note that: "Without a thorough engineering analysis of tornado damage in any event, the actual wind speeds needed to cause that damage are unknown" However what is clear is that F5 damage requires significant occurences to occur, which to my knowledge have not at Greensburg.

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

Looking to the enhanced Fujita scale, which has upper bound, lower bound and expected analysis of wind speed required to cause certain types of damage to buildings. See the link below.
http://www.spc.noaa.gov/faq/tornado/ef-scale.html
Now to categorise as an EF5 the tornado must have indicators suggesting windspeeds greater than 205 MPH. A look at the common damage seen at the site of the Greensburg tornado for all different sorts of structures reveals  that even if we take the Upper bound value(which is really not a good expectation, the estimate is far better), the maximum estimate of damage visible in the town is of the order of 200MPH. Now with the true value of windspeed being much closer to the estimate it can be seen that the likely windspeed occuring at greensburg was somewhat below the EF5 threshold, and therefore the tornado probably should have been classified EF4.

Another interesting thing ive just noted is the removal of car displacement and asphalt ripping from the wind speed estimates, which I think is a strange move. Additionally the EF scale basically ignores how strong a tornado is after the point is reached when the windspeed becomes sufficient to be lethal to those in well built structures above ground. So hence upper level F3 and F4, F5 all fall into this category.

In Moore i completely disagree. The displacements of the cars and their mangling indicate an extremely intense tornado, and multiple structures were quite literally blown away. Just take a look at the damage in Greensburg to note the difference in tornado strength between the two(if you really want to blow it away look at the damage from Jarrell) Not only this but doppler indicated windspeed indicated a strength near 300MPH, which is more than reflective of and F5.

Hence considering the significance of the event, the Greensburg tornado was likely bumped up to EF5 to ensure adequate funding for the rebuild.

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.


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?

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.