Tornado Alley Outbreaks and Severe Weather Worldwide

[David Carroll]

Jimmy,  

Im far from an expert in relation to others on this forum. Mike is correct, i was mainly providing my opinion just on many other experts I have talked with.  I have to say, they also have their opinion on whether it was a EF4 or EF5.  This has opened my eyes to what one can expect when chasing storms of this magnitude.  

The photos provided were of a driver also a photographer, not from a media person.  John sent me these photos after the interest I showed, considering we never got to visit Greensburg.  

Its just such a shame so many people had to lose their lives.  

http://www.spc.noaa.gov/climo/reports/070504_rpts.html - This report says it all.  

Dave

[Mike]

The new EF scale just expands the wind speed perametres from the old one.  And as David said it's just an opinion of what 'he saw' - not what he believes whole heartedly without expert qualifications to which none of us have in this determining this damage.   

Mike

[Jimmy Deguara]

David,

Fair enough - thanks for elaborating.

Mike said..

The new EF scale just expands the wind speed perametres from the old one.

Mike, this is only one of the enhancements: there are others that may have been mentioned earlier.

Regards,

Jimmy Deguara

[John Allen]

The EF scale actually takes note of the type of building/structure, not just the damage done to that building. It actually disregards windspeeds somewhat, with EF5 being anything over 200 mph: hence leading to little definitive difference between something like Jarrell or White deer and something like greensburg(which as Jimmy has eluded to is questionable, although i doubt we will know for certain).

[Mike]

 :)  Healthy discusssion and debate is what it's all about!

The EF scale does use 'wind speed' as set out by met people and wind engineers as they condensed the gusts somewhat and yes, have used the following also to compliment the scale.

 The EF scale still is a set of wind estimates (not measurements) based on damage.  It uses three second gusts estimated at the point of damage based on a judgement of 8 levels of damage to the 28 indicator list.  The 3 second gust is not the same wind as in the standard surface observation.  Standard measurements are taken by weather stations in open exposures using a directly measured one minute speed.

Reports were of wind speeds of 205mph which would rate it EF5, but what rating would they give it if it hit the same place last year? They would have rated it an F3 or F4 depending on the fastest 1/4 mile speed or the 3 second gust!

Mike

[David C]

Reports were of wind speeds of 205mph which would rate it EF5, but what rating would they give it if it hit the same place last year? They would have rated it an F3 or F4 depending on the fastest 1/4 mile speed or the 3 second gust!

Mike

Are you sure about that Mike?

The important thing here is that the emphasis is on damage, not wind strength. The 'windspeed' is simply an inference based on damage. They would have rated Greensburg v2006 based on a damage assessment, from which an F rating would be assigned ( I would say F5 based on cleared foundation subject to this thread's raison de etre). From the F rating, one could infer wind speeds  according to the F-scale only. As it is, it was rated EF5, implying wind speeds greater than 200mph under the EF scale, but that's all. You cannot used wind speeds inferred by an EF rating to slot it into the F scale to determine an F rating.

[David C]

I guess I am not an expert but the damage simply did not add to what I had percieved to be EF-5 rating from descriptions such as those in May 3 1999 and Jarrell, Texas in 1997. What David Croan may be saying that there may have been multivorticies that could have created regions of locally EF-5 'maximum rating' (please correct me of I am wrong in my assumption David).

Hi Jimmy. Yes, suction vortices are one possibility for areas of locally enhanced damage. The EF (or F) scale does not consider how widespread the damage is in assigning an rating, but simply whether or not such damage exists and is attributable to the tornado. It does appear that, as far as Greensburg goes, the damage was not as 'complete' as Moore -- I know this is based on the opinions of damage assessors that you are in contact with who have observed both damage tracks. That's fairly compelling evidence I think. Nonetheless, this was a big tornado and will go down in history as the first EF5.

[Mike]

Oops, sorry David forgot the 'E' in front of the latter part of my reply referring to 'F' ratings - my mistake, so your last part of sentence won't refer to that Allengans contraria non est audiendus   Back at you!

I'm content with the views anyway posted here.  I wasn't trying to add inferences to the F rating as I know it's not to be used now - and I'm aware that damage for EF4 and higher are rated on damage to well well-built constructions that are destroyed - but this argument will go on forever without a definitive answer.  We can speculate, assess and conclude but in the end nobody knows how powerful these things are and that's why the science continues.

Mike :)

[John Allen]

Since when do we speak foreign tongues here? Im confused LOL. As far as i can tell David has gone to French, and Mike looks like hes writing latin: but i may be wrong.

David,
as suggested and allayed with evidence above I think we concluded that rating this tornado an F5 was rather inappropriate given the assessment of the damage. However when using the new rating system(which i am not overly supportive of from a research perspective) an EF5 damage swathe was quite likely present in some part of the field, although as outlined by Jimmy this could be attributable to debris projectiles due to the large radii of the strong winds. Either way, it has been rated an EF5(possibly for publicity but who knows), and we still do not enough about tornadoes and tornadic behaviour to question that assertion(even by comparing damage assessment). In my view on the old scale it would barely rate F4, but thats my considered opinion.
 
Edit: Spelling

[Jimmy Deguara]

Hi John,

In my view on the old scale it would barely rate F4, but thats my considered opinion.

Can you elaborate on this comment? So what does it rate in your books on the EF scale? Sorry to cover old territory but this quote puzzles me somewhat.

David, yes I am thinking of the sub-vorticies as perhaps some explanation of possible more intense damage locally. What are your comments regarding the possiblility of large masses of debri being carried around creating perhaps more damage as it may seem? I note on a documentary - take what one wants from it but known research experts were commenting about the possibility that the 1997 Jarrell accummulating appreciative volumes of dust and debri causing perhaps more intense damage than one would have anticipated. I realise this is only a generalised depiction of thsie statements but it is food for thought.

Regards,

Jimmy Deguara

[John Allen]

Fair enough Jimmy, I will elaborate:

By my conclusion on the EF scale I see no damage present to suggest an EF5(with its associated structure damage), however I realise that without actually being officially on site this is hard to confirm. From what I have seen and evaluated using the damage scale the highest possible damage i can see suggests High EF4.

Reasons for my feeling on the Fujita Scale:
1. These are the respective definitions from NOAA for the F scale:

F3: 158-206mph : Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown. Example Here: notice similarity to much of greensburg, also you see some of the damage criteria apparently being met.
http://www.spc.noaa.gov/faq/tornado/f3.htm

F4: 207-260mph :Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated. Within the damage images ive seen I feel that this category reflects the maximum extent of what happened at Greensburg.
http://www.spc.noaa.gov/faq/tornado/f4.htm

F5 261-318 :Incredible damage. 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.To me it is clear that this isnt apparent at Greensburg.

2. Even using the enhanced Fujita Scale there is no evidence to suggest windspeeds that reflect a rating above F4. However I do know that the FScale windspeeds are not to be taken for gospel as they are unverified(mind you the same can be said somewhat for the EF scale). No damage criteria are met to raise the windspeed above 210 mph, hence also suggesting low end F4 by Fujitas original work. I dont believe this is as conclusive as point 1, although it is true IFF the winspeeds on the Fscale are ballpark.

From these definitions and what i assessed from photos using enhanced fujita I can only conclude that at most this tornado would have rated an F4 on the orginal scale.

If anyone would like to see my full assessment notes I could organise to post them once i begin Uni holidays.

I hope this answers you questions Jimmy,
John.

[Jimmy Deguara]

Hi John,

No what I am inferring is that I thought that the new EF scale keeps the damage consistent between both scales and adjusts the winds based on current knowledge.

Also, I note Brad had asked for further explanations and also you had drawn attention to ripped asphalt - thence possible EF-5.

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.

Any comments here?

Regards,

Jimmy Deguara

[John Allen]

Definitely not Jimmy: there is not that much consistency in the damage scaling noted: Jarrel wouldve been rated an EF5 and but for imagery of the event people would liken it to greensburg purely on the basis of that statement: as you have referred to apriory the damage between these two events is not consistent. There is no real analysis if the tornado is above the EF5 threshold: it just becomes an EF5. I believe this is a serious flaw and non reflective of actual damage. While the more detailed analysis of behaviour under wind speeds is very useful it has limitations: certain towns may not always have those structures and thus the damage could be underrated.

 Sorry i missed that remark Brad. If you look at the area surrounding the road in that particular image you can see a dark brown scaring around a black surface: this is consistent with other images i have seen of intial asphalt ripping(it works its way from the edges). Unlike other strong events this one did not appear to do as much ripping, but this is a feature noted with very powerful tornadoes(F4+) such as those mentioned earlier in the thread. It is my opinion that this could have been the location for the EF5 rating near to this point as if this is an area of highest windspeeds there is likely a continuation of that swathe through houses. This would be where i wouldve looked for damage in order to find the worst of it. That was the basis of what i was saying.

Hope that clarifies.

[Mike]

Yes, It's Latin in both.  Thought he was trying to out-gun me.



The Jarrell rating was F5.

 Is John saying that they wouldn't have or would have rated it F5 if it was not for the photographic/public evidence that came from Greensburg? ( per John's sentence -: Jarrel wouldve been rated an EF5 and but for imagery of the event people would liken it to greensburg

They're not going to reclassify events pre-2007 to the new Ef scale,they've already rated Jarrell.



  Does anyone have info on re this: Jarrell's F5 tornado at its beginning caused crop dirt to be ripped out to a depth of 50cm (20 in), so was there evidence of anything similar in Greensburg?

Edit: 8 in changed to 20 in

What the governing authorities have to clarify is how far does 'Devastating damage' for EF4 and 'Incredible damage' for EF5 go in order to define each? From what I've seen from Jarrell and Greensburg photos there's not a lot to question re extent of damage.  By reading both the table of contents that cover EF4 and EF5 effects - just about everything (damage wise) that happened in Jarrell was mirrored in Greensburg.

Mike

With the wind being gauged at 205 for Greensburg it's an EF4 - but like we've all said all the way through the thread - there are areas which sustained damage caused by debris that reflected EF5 scale characteristics.  We can only go by what the authorities tell us and take it as face value.

[Jimmy Deguara]

This thread I think now is becoming clogged with various opinions and in some cases conflicting information that for any reader may become confusing - I guess it could then detract from the original topic and the original debate.

Thanks for all the worthy discussion - I think I will have this closed with perhaps permission from any member with anything new updated information related to the topic such as links to reports etc to be posted by the moderators.

Regards,

Jimmy Deguara