Australian Severe Weather Forum

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.

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

Sorry i didnt clarify this sooner, commonly in scientific work the third person is used instead of the first person. Particularly when im working on all these assignments I mistakenly use scientific 3rd person. Its simply my opinion(and that which im attempting the convince the reader of).

Quote from: David Croan on May 16, 2007, 09:43:20 PM
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

I request that you back up your assertion that a a comparison to a supposedly similar strength(EF5) tornado is not valid? In my view while all tornadoes are different, it is likely that they contain consistent elements with respect to damage elements, hence on this point I justify my comparison with Moore.

My hypothesis is thus(if you didnt gather it from my posts):
Given the damage visible from the Greensburg tornado(as shown in imagery which i will further clarify below), I believe that it is possible that the damage assessment may have been compromised on the premise of being a close to EF5 adjusted upwards for sympathetic or historical reasons. My points are attempting to justify this hypothesis.

Quote from: David Croan on May 16, 2007, 09:43:20 PM
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.

To back up my assertions on this point: I have viewed countless images(im talking hundreds im really interested in this) from Greensburg in order to perform this analysis(which i did using the exact EF scale, as outlined by the NWS), and based on this analysis concluded that we have a high end EF4 event rather than an EF5.(note that I havent posted each image and what it correlates too to save space, and your time, ive actually filled a small notebook with my notes) Now while this may not be the best method of damage assessment via images, it is a darn sight better than just coming out and saying it was EF4. The high end EF4 conclusion is reached by looking at the various buildings and performing a damage analysis(visible) on the structure. From this conclusions can be drawn from data obtained via intensive study in wind-tunnel systems. I am simply saying that the damage visible reflects more than likely a maximum upper bound limit, rather than a good estimate of the tornadoes actual strength. Hence adjusting down slightly I conclude we likely have high end EF4. This is what my analysis was intially performed on.

In addition to this, I thought i would just run a comparison to the Moore F5 event and other events of a similar class(F5's are certainly EF5s). From what the comparison's show it can be seen that:
1. The debris does not appear  to be swept away from the structure it came from, which is unlike the other events(take for instance Andover)
2. The vehicles that do appear in Greenburg are relatively undamaged, thus suggesting they havent been moved far. This again is contrary to what was seen in other events(where we have displacement of near a 1/4mile).

There are probably other points that could be made, however I agree with David that comparison of a Top end F5 event is not prudent for a low end F4(low end EF5 at maximum).

Quote from: David Croan on May 16, 2007, 09:43:20 PM
When all is said and done the Fujita Scale is a damage assessment scale, not a measure of a tornado's maximum intensity.

Just to clarify for you David:
Quoting directly from the SPC: http://www.spc.noaa.gov/efscale/
Dr. T. Theodore Fujita first introduced The Fujita Scale in the SMRP Research Paper, Number 91, published in February 1971 and titled, "Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity". Fujita revealed in the abstract his dreams and intentions of the F-Scale. He wanted something that categorized each tornado by intensity and area.

And from this Fujita found that a way to deduce the maximum observed intensity of a tornado was via a damage assessment of its path.

Quote from: David Croan on May 16, 2007, 09:43:20 PM
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.

Here I completely agree. Fortunately or Unfortunately(depending on the resident or scientific perspective), the storm went through a cyclic mesocyclone phase just after the town, limiting the evidence available to assess the tornadoes intensity. I too would like to know how intense tornadoes get, and hence why i take such interest in this debate. At this stage I don't believe the movement to EF rating is really reflective of what we want to know about the tornadoes. As you say the rating(which is all the rage) doesnt matter: what would be interesting is to compare the circulation strength of storms to the tornado generated by those storms: and this would particularly be interesting for the high end events. Maybe something like this could constitute a piece of research or thesis I will do in the future, Until then it is an unknown quantity. However I do believe the original Fujita scale is useful to seperate the relative power of events, and hence why if the fujita ratings were still used I would dispute the assessment that such a tornado was F5(which damage suggests it is not).

Hope that straightens things out.


NB:
The images of the Jarrel multiple vortex stage are some of the most amazing images ive ever seen, and id truly like to find out more about how split main vortexes occur, and why it is such a rare occurence. This may sound sad but seeing tornadoes, both big and small has always got me excited and rushing off to find out more, and while i detest when they impact on peoples lives, I truly am constantly amazed by this phenomen of nature.


(sorry John I butchered your post formatting)

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.     

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?

Regards,

Jimmy Deguara

I request that you back up your assertion that a a comparison to a supposedly similar strength(EF5) tornado is not valid? In my view while all tornadoes are different, it is likely that they contain consistent elements with respect to damage elements, hence on this point I justify my comparison with Moore.

Hi John - good post! We may be talking a slightly different language here. IMO, a comparison based on photos as available on the web - which is all we can do here is not valid for discerning tornado intensity. You commented yourself that Jarrell damage was on a different level. My point exactly - one cannot use photographic evidence of Jarrell as a standard by which to compare all other EF5 tornadoes.  I have never suggested that Greenburg (or Moore) was the more intense tornado - simply whether or not Greensburg is EF5 or EF4. One EF5 tornado might clear the foundation of a complete row of houses (or whatever the criteria are with the new scale). Another EF5 might only clear the foundation of one house. The foundation of at least one house must have been swept clean in Greensburg for that rating to have been given (it seems you cannot find evidence of Ef5 damage from the web, hence your reason for EF4!). This is irrespective of whether Moore drilled a hole 1 mile deep into the ground and struck oil! Both are still EF5 despite photographic evidence suggesting one being more intense than the other based on the 'impressiveness' of damage. Do you understand my point?

From the evidence I have seen, Greensburg has set the upper limits of low-level mesocyclone intensity in recent years. This was a cyclic storm and different to Moore which was in a remarkably steady state by all accounts. We did not have all the GrLevel3 data around in 1999 either so we cannot say which storm had the 'Moore' intense rotational velocity (sorry, could not help myself). It would have been fantastic if a DoW was taking measurements of the Kansas tornadoes to compare with the 319mph  +/- velocities recorded in Moore.

Bang on David, its good we are starting to talk on the same wavelength.

My assessment comes from the damage photography available, and in this respect I cannot see anything that warrants more than an EF4 rating. However my questioning comes on the back of the photos being provided by the Media, which naturally has a tendency to seek the most destructive or horrifying images in order to control the press. Hence if there are no images indicating EF5 damage: the question is where is the EF5 damage? The media would naturally gravitate to the most damage they could possibly find, thus likely providing an image of it.

The impressiveness of the damage does not sway my opinion of the comparison: what I was arguing was that since EF5 supposedly encapsulates F5 tornadoes: shouldnt we see comparable aspects within the damage path or are we just using a flawed system, which will never reflect the tornado intensity properly.
That particular comparison is not as strong as the actual damage evidence ill be the first to degree, although it should be considered.

From the imagery available showing the rotation of Greenburg, you are right in your conclusion that it was clearly one of the most intense mesocyclones in the period of the technologies use. On the poor meteorological pun I must say this: while we cannot tell which had the more intense rotational velocity at the mesocyclonic level, what is evident from the damage is that Moore likely had a far more intense rotation at ground level as compared to Greensburg. This raises the question that with GrLevel3 data are we able to directly correlate mesocyclonic rotation to rotational speed within the tornado itself? Or is their a loss between the two systems which is unpredictable resulting in fluctuant tornado maximum velocities for certain mesocyclone intensities.

Just reading back through that: I apologise for the use of grossly technical terms outside of the Advanced Meteorological discussion.

I must say David, im enjoying this debate kinda reminds me of arguments in "The Meaning of Life" 

Here's my 3 cents worth.

Does it really matter how close this tornado was to EF5 scale?  In reality when i look at Greensburg which was 95% flattened, I don't really care if it was 3mph short of an EF5 'damage' scale.  What constitutes an EF5 event that satisfies everyone?  The town ground down to dirt?  There were cars wrecked and flung around, there were structures that were obliterated that were'nt in the 'ground zero' section of the funnel.

There are reported cases of F0 tornadoes having the same damage path as an F4 purely on the assessment of the engineers who viewed the damage scenes and reports on F4 wedges having the comparible damage to an F2.   Just because there were not particular items that were obliterated in relation to damage to Moore, Jarrell what does that matter?  This storm was very vicious in its structure as we've seen also that it produced so many tornadoes from one storm system proved that. (even another EF2 was sighted heading for the town but lifted after the EF5 went through Greensburg!)

It must be remembered that the perameters set by these scientists for the F scale or the new EF damage scale have not been proven scientficially at all.  The margins they use are 'a guide' to damage assessment dependant on what structures are destroyed.  Does a trailer park obliterated off the face of the planet and vegetation stripped constitute and EF4 even though sightings of the funnel were of a marginally wide stove pipe for example?.

From the city before and after satellite pics would you rate the damage as high EF4 or low EF5?  Jeepers, the wind perameters for both are negotiable.  Surely it really doesn't matter only perhaps for the record books - but doesn't 95% of the observers say it was an EF5?  Don't the scientific results, observations from the NWS agree on the wind profiles etcetera?

How can we ever determine EF5 damage if we dissect how many leaves were left on a tree or how many vehicles resemble rubbish bins?  Greensburg's water tower was totally destroyed and that thing is not a small, light landmark!!!

For my 3 cents if the thing was 3mph slower in wind speed to rate an EF5 so what.  Those damage ratings are variable - that's why they restructured the Fujita scale and no doubt will do so again with the EF version.  Otherwise they would not have adjusted it at all if those perameters were gospell.



Mike

I think you missed altogether the point of this debate mike: we are considering it on the basis of difference in funding.

Greensburg was not 95% destroyed: rather 95% damaged, large portion beyond repair. There is a significant difference: additionally you will note that only the local official made that comment, which is part of why this debate arises: were there vested interests within the damage assessment? Clearly that town official is to benefit if people consider his town that worse off that it needs even more funding to repair.

The point of Greensburgs water tower being destroyed raises an interesting question:
An object being heavy does not matter, water towers while heavy have relatively weak support structures, together with large surface areas and a height within the maximum windspeed range, hence more than likely they will be damaged or destroyed.


We are not contesting that this was a very powerful storm that did vast damage: what we are contesting is a blurring of the rating guidelines in order to secure more disaster relief(which if you think about it is fraud).

While I agree that we are only using an arbitrary scale I dont believe it is prudent to ignore it: by categorising we can use storm dynamics in order to better predict the strength of tornadoes they produce: There is method to the madness

So sorry if i misread some parts, was not stepping on toes at all!  I see now.  Well in that case there definitely is a course for comment!

I did not know that there was a 'case' for more funding.  I would have presumed that whatever relief would come it would be 'across the board' given the damage.  (destroyed or damaged - if my home was wiped of it's foundations I'd call that destroyed and 'beyond repair' really is not 'damaged' is it.  'Damage' really is a bit ambiguous when your lounge room is next door!)

Why or who on earth in the USA is quibbling about how much it takes to rebuild the poor town?  Oh dear, i can see this is going to be another South Carolina without even to this day the government doing what it should to get the place cleaned up.

I take it all onboard and have nothing else to say!  You'll forgive me as I know nothing about the claim for extra funding - more to my fault guys sorry!

Mike

Yep John, it's clear that there were probably only a few spots of EF5 damage in Greensburg (ie based on the damage assessment that resulted in the rating). I'd say there must be some uncertainty with respect to those spots of damage and this has resulted in some questioning the initial rating. Obviously we are dealing with a spectrum of events - this tornado would probably be at the low-end EF5 (or EF4 depending on how flawed the assessment was). All this notwithstanding, boy, what a scary storm - some are suggesting the tornado that developed north of town was possibly more massive (as in width)!

Ive gotta say, such a concept scares me immensely. This tornado was big enough, and yet the damage swathe of the next appears even larger: What interests me is what within storms causes these giant variations within the wind swathe of a produced tornado? What causes a storm to produce a massive tornado with wind that has been experienced in a much tighter vortex?

Additionally I think that Greensburg can consider itself fortunate that the formation of the second tornado did not occur over the town while the first was still in progress. Given the country the other tornado moved over I would not be surprised if the vortex was of a similar strength, but did not have a chance to do damage like that of Greensburg, and by the time it did the storm had weakened somewhat.

I have also found a site which has some damage that may reflect this EF5 rating, although i dont agree with this chaser plunging into disaster zones in order to obtain footage to sell, I feel that the images obtained are very interesting with looking at what this tornado did.

http://www.ultimatechase.com/chase_accounts/Greensburg_Tornado_Damage_Survey.htm

Images 2, 9, 11, 20,35 Show seriously translocated(and smashed) cars, which would be expected with a original F4-F5 event.
Images 15,17,19,26,32,38 Show homes and buildings with pretty much nothing left standing, and some with exposed slabs, one of these images is part of what i suspect may be part of the EF5 identified swathe(have a guess which one and it may not be obvious without looking at EF scale). 

While I in no way condone those who take pictures of damage for selling reasons, I believe that such information is highly useful in assessing events such as these.

These are truly frightening creatures of natures creation, and should be treated with all due respect(not like those idiots who got in really close to the tornado pre-greensburg(they have done the same for Hurricane Katrina)).

John,


Although these are possibly the two main tornadoes it produced of such massive size, please do not think it had weakened. I think to produce two massive wedges is a thing in itself. The storm went on to produce multiple touchdowns with significant tornadoes possibly over a few hours based on its warnings though I will await the final assessment. Definitely by midnight, the storm was a stock standard tornado producer with not so extreme velocities.

I agree with David the second tornado produced a wider path.

Please note these are county based assessment ie Kiowa County. Other assessments may be made by separate NWS offices or other teams.

Another interesting point made by analyses of radar is that the Greensburg tornado may have veered and come back into the eastern side of town and then merged with the second violent tornado.

Regards,

Jimmy Deguara

Thanks for the link to those photos John.  They are truly amazing photos - regardless of them being sold to the public or whatever - i agree that they are immensly useful in assessing damage.  I particularly liked the one with the young girl on the swing amongst the carnage - innocence in the face of diversity.  Wonderful stuff.

If the difference between EF4 and EF5 damage is a few extra branches snapped off then from viewing those photos really justifies whatever relief funds are needed.  I've never seen anything like it - thankfully and surely these images must lay to rest that this tornado was just inexplicably monstrous whatever the argument is about relief funding - I just can't see the point in it looking at the damage!

Mike

A friend of mine, who was riding with Jimmy on the night of this tornado, suggested to me that this tornado changed his whole view on storm chasing. Now, talking deliberately around Jimmy, since he would have his own perspective given that these guys saw the tornado,   he described seeing the massive tornado (relying on lightning illumination, remember) and, soon after on approach to Greensburg, he described the intense pungent smell of gas, the continual moan of sirens (as in emergency vehicles not tornado sirens), damage, and a overwhelming sense of catastrophe on a scale which he had never experienced (and few people would experience). It was very fortunate that the second massive tornado did not hit any major towns.

Anyway, w/r to the tornado track above, note the 2nd major tornado very rapidly becoming VERY large - what a dangerous situation for spotters or reckless and / or inexperienced storm chasers. I would not want to be close to that first tornado, but if you were east of town you would have been in for a nasty shock as tornado 1 slid by northwards and a few miles to your west.