TORNADO DAMAGE SURVEY: COLLIN/GRAYSON COUNTIES TEXAS

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
350 PM CDT WED MAY 10 2006

...INITIAL RESULTS FROM DAMAGE SURVEY IN COLLIN AND GRAYSON COUNTIES
FROM STORMS ON MAY 9TH 2006...

NATIONAL WEATHER SERVICE METEOROLOGISTS CONTINUE TO SURVEY DAMAGE
FROM TUESDAY EVENING`S TORNADOES ACROSS COLLIN AND GRAYSON COUNTIES.
THE SURVEY TEAM FOUND DAMAGE FROM APPROXIMATELY 2 MILES
EAST-NORTHEAST OF ANNA IN COLLIN COUNTY TO 2 MILES SOUTH OF
WHITEWRIGHT IN SOUTHEAST GRAYSON COUNTY. A SMALL BREAK IN THE
DAMAGE PATH EAST OF ANNA WAS RECENTLY FOUND...SUPPORTING SPOTTER
REPORTS OF TWO SEPARATE TORNADOES. THE WORST DAMAGE TO SINGLE FAMILY
HOMES...JUST NORTH OF WESTMINSTER NEAR AND EAST OF FM 3133...HAS
BEEN RATED UPPER F3 ON THE SCALE.


NATIONAL WEATHER SERVICE METEOROLOGISTS CONTINUE TO SURVEY THE
DAMAGE AND ARE WORKING WITH WIND ENGINEERING EXPERTS TO PRODUCE A
MORE DETAILED DAMAGE ANALYSIS AND SUMMARY.

AN UPDATED PUBLIC INFORMATION STATEMENT WILL BE ISSUED LATER TODAY.

More information from the NWS Fort Worth can be found here:
http://www.srh.noaa.gov/fwd/collintor06.htm[/b]

Will post information later, Mike
 
It should be noted that the rating is preliminary; however, if it remains F3, I think the main argument (not that I like this one the least bit) is the slow (10-20 MPH) storm motion.
 
Amazing...another high end F3. I wonder why so many tornadoes this year are clustered right in that 190-200 mph range. Hmmm... :blink:

OK just reviewed damage photos and I have to admit I'm perplexed. There are houses that aren't there. Not a stick of them is even in the shot. No teddy bear, no water heater, no nothing. Nothing!!! Everything was swept away!

If thats an F3, what does an F5 do? Take chunks of land and throw them thousands of miles?

Sorry, just really confused. It seems the top end of the fujita scale is an F3 now...I mean I know it isn't but could someone with damage survey experience please explain.

Thanks.
[/b]


Building practices for the structures hit are taken into consideration when making an assesment Alex. Without going into an hour long explanation of strapping, different nailing ie (toenailing, etc.. ) that is a good explanation to try to answer your question.

Tim Marshall gave an excellent presentation at the 2006 chaser convention on damage assesment. It was very informative.
 
When there is NOTHING LEFT on or anywhere near a foundation, unless that home is a prefab, a mobile home, or not anchored to the foundation, it should be violent damage.
 
I wouldn't be shocked if they bumped this up to a lower F4 for the final rating. There are a couple of what *appear* to be (and therein lies the problem of 'virtual damage surveying' lol) well-built homes that were reduced to foundations with most of the debris removed at least a short distance downstream. Also was very impressed by the level of ground scouring seen on the damage path flyover done by the WFAA team out of Dallas (http://www.wfaa.com/).
 
Did anybody see in the television station video, after the shot of the scoured path in the field, they panned right (E/SE?) about a 1/2 mile and there was a pickup that was pushed off of its driveway out in the field about 80 yards? (You could see the tire marks as it was pushed through the field - sideways). It hadn't been picked up, hadn't rolled. Just slid straight sideways for quite a distance.

Would that possibly (probably?) be caused by RFD winds? It was far enough away from the scouring (and pushed in virtual straight line) to make me think it was not the rotating tornado winds *proper* that caused that.

Any thoughts?

Darren Addy
Kearney, NE
 
When there is NOTHING LEFT on or anywhere near a foundation, unless that home is a prefab, a mobile home, or not anchored to the foundation, it should be violent damage.
[/b]

Yes, I think you're right. In the aerial video you can see F2 damage with some houses, F3 damages, but in some cases you could see also F4 damage with at least 3 or 4 well constructed houses filmed by the cameraman that seem to be leveled.
I think that low end F4 could be a better classification. Anyway I didn't go in the path of the tornado to take a look with my eyes so I gave only an opinion.
 
Yes, I think you're right. In the aerial video you can see F2 damage with some houses, F3 damages, but in some cases you could see also F4 damage with at least 3 or 4 well constructed houses filmed by the cameraman that seem to be leveled.
I think that low end F4 could be a better classification. Anyway I didn't go in the path of the tornado to take a look with my eyes so I gave only an opinion.
[/b]



I didn't get to do much in the way of chasing this storm Tuesday night since I had to go to work but I did capture some amazing shots of the meso looking north toward Mckinney. This storm developed rapidly as the cap broke and organized very quickly. The devesation caused to homes by this tornado was tragic F3 with possible F4 damage... in Collin county that's unheard of.
 
Before folks start spouting the anti-F4/F5 conspiracy theories again with regard to this tornado event, consider that the damage survey team included two members of the national Quick Response Team (QRT) that have extensive tornado and wind engineering experience (namely Gary Woodall and Tim Marshall).
 
Impressive tornado damage, yes, but do we need to always draw the conclusion that it was a violent tornado simply because a foundation was wiped clean? All that have posted here were around for the last discussion (the TN high-end F3), and we now know that the houses that were wiped clean were poorly constructed (lawsuits are pending regarding shoddy construction).

In the past, this tornado probably would have been rated F4 (based on Fujita's rough categorization). Yet, we now know that it doesn't take 200 mph winds to do the damage that was done on Tuesday night. So, in the name of good science, we must not jump to conclusions every time we see a leveled house. I'm quite certain the people who conducted the damage survey of these tornadoes are far more experienced than most of us combined.

Gabe
 
Excellent points Greg and Gabe. The tornado damage surveys can tell a lot more than generalized damage path pics and fly-overs by media can present. You have the most expert damage survey people around in that area and that rating was probably scrutinized more than most surveys are. Whether it's an F3 or F4, it was still very bad damage and certainly had a terrible impact on the community of Westminster and the surrounding area.
 
Speaking of disappearing F4/F5's -- check Dr Doswell's latest http://webserv.chatsystems.com/~doswell/EFscale_rant.html
[/b]


F4's are endangered, F5's are extinct. I don't always agree with Doswell but I think he really hit the nail on the head with his latest rant. Someone in the Gallatin, TN thread mentioned the some government conspiracy theory and Doswell may have found it... Too damn cheap to fly in the survey team. The new scale is only adding more inconsistency to the already inconsistent record. Why any scientist would do this baffles me. Why not have an F and EF rating? This way we get some consistency to the ratings and an injection of the "new" science. I thought the Gallatin, TN tor was an F4 with all walls collapsed on the foundation. The TX twister damage looks worse with at least one foundation totally swept clean of debris with only a rather large heavy duty fireplace left (which would probably survive an atomic blast). Looks F5 to me.

I've got this F-scale figured out:

F0/F1: Rating OK (though watch out for the bogus FGF F1 gustnadoes)
F2: Add +1 to the rating if some walls are down. If tornado was "slow" moving consider adding +2.
F3: The new "violent" tornado category. Always add +1 and consider +2 for particularly severe damage.
F4: The new rating for May 3, 1999 Moore, OK tornado.
F5: What the hell is that? 1. Mount St. Helens horizontal blast or 2. Evacuate area immediately to avoid radiation as it was nuked by Iran.

USING THE NEW ENHANCED FUJITA SCALE GUIDELINES...MAXIMUM WINDS WERE LIKELY IN THE 150 TO 160 MPH RANGE.[/b]

Likely? Likely much higher. Let me see. Hurricane Charley had 145 mph sustained winds and the homes in Punta Gorda didn't get flattened like those in TX. Andrew was stronger and while homes sustained severe damage they wern't picked clean. I might be comaparing an apple to an orange but wind is wind. I think the EF wind scale is a joke.
 
Doswell may have found it... Too damn cheap to fly in the survey team.
[/b]

Pride could have as much to do with it as money. It would be embarrassing to call in the QRT and have them berate you for wasting there time with damage below the criteria for F4/5.

Likely? Likely much higher. Let me see. Hurricane Charley had 145 mph sustained winds and the homes in Punta Gorda didn't get flattened like those in TX.
[/b]

The construction practices in hurricane prone FL are hardly comparable to those of rural north Texas. Hurricane winds are also largely horizontal (there are believed to be considerable vertical velocities near the ground in tornadoes) - strongest in a very small swath, and almost never actually measured but inferred based on merging the observations with models, and based on an assumed surface of WATER and not the much rougher land surface that considerably slows the winds. So - it is non-trivial to compare wind damage from a hurricane with those from a tornado to infer wind speeds for a number of factors.

I liked Chuck's essay as well - frank as usual, and agree also that the EF scale really blows (pun intended) in terms of getting meaningful information from the tornado database, despite the well intentions of those who are promoting it.

Glen
 
It's obvious that we are trying to move to the idea of classifying tornado based on wind speed. Well, perhaps I should say that using more damage indicators and more degrees of damage helps to provide many more categories of damage to which wind speeds are assigned. Fujita's original scale made no mention of gas station canopies, or the majority of other structures, natural or artificial, that are much more widespread than 'well-built homes'. It would seem that, for objectivity, to more damage indicators and degrees of damage, the better. Of course, there's a point at which we can't confidently say that this-or-that damage was from 5mph higher wind speeds than that-or-this damage. In regards to more detailed damage indicators, and, thus, a refinement of wind speeds available for assigning to tornado segments -- The new EF scale tries to do this (i.e. radar data may be used to support a given EF rating), and F-scale ratings the past few years seem to have done this as well. Should we keep our blinders on and continue to shunt recent engineering work by rating tornadoes based on the brief description given by Fujita (part of which Alex quoted above)? Isn't science about advancement? Isn't it about using new research in the search for truth (in this case, the actual intensity of the tornado)? Are you personally offended when EXPERTS, people like Woodall and Marshall, don't agree with your personal observation? Sure, they can actually look at how the house was built, how the walls were attached to the foundation, but surely we, from our computer hundreds of miles away, can do just as well by looking at a few relatively low-resolution pictures taken by media and other folks. Heck, what's the point of damage assessment if we can just survey everything by online pictures?

As Gabe noted, 15 years ago that tornado probably would have been given F4 (or even F5 with a cursory look at the pics). Perhaps it makes people feel good to know that there was an F4 or F5... I know people tend to want to think they lived through something as bad as it can be (there has been phsychological research into this in regards to hurricanes -- people tend to want to think they lived through something that's as bad as mother nature can dish out... I mean, how many people really experience Cat 5 winds in Andrew?) But, we're moving on, trying to use some engineering realities to remove one more complication from damage rating assessments. We have enough problems with the fact that we can only really judge tornado intensity when structures get hit (even this is being diminished in the EF-scale, with the use of different damage indicators like hardwood and softwood trees). In the past, we've also had a problem with the fact that the EXACT same tornado could be rated entirely different depending upon what type of structure was hit (and, more importantly, how well the hit structure was built). I'm not talking about if the tornado hits an outhouse or a big house, I'm talking about if it hits a house in one development versus another development. Of course most houses today are going to look "well-built", but that's obviously note the case. If we are seeking to rate a tornado as objectively as possible, trying to assess a rating based on the tornado REAL strength, isn't it in the best interest to remove as many complications as possible?

EDIT: Re-reading this, it comes across a bit harsh in areas. No offense intended, obviously! :D
 
Pride could have as much to do with it as money. It would be embarrassing to call in the QRT and have them berate you for wasting there time with damage below the criteria for F4/5.

Glen
[/b]

I think you hit the nail on the head, Glen. After the La Plata, MD snafu, I think a lot of have been a bit more reluctant to give the violent tornado rating. During that case, the press reported that the event was a rare F5 tornado, only to discover that the "F5" tornado damage was only indicative of strong F2. Talk about embarrassing! Was this the case for the survey of Tuesday's tornado in north Texas? I don't think so. But, I imagine there have been other damage surveys where this played at least a minor role in determining the tornado rating (F3 vs. F4, etc.).

Gabe
 
Isn't science about advancement? Isn't it about using new research in the search for truth (in this case, the actual intensity of the tornado)?
[/b]

I don't think you'll find much disagreement with that - but there is good reason not to flush the current tornado database down the toilet in the name of advancing science when it isn't entirely needed. Why not adjust the wind speeds down for the old F scale categories, instead of adjusting the damage indicators toward lower EF categories? Why not have a clean swept, well engineered home still be classified as F5, and simply open the door for F6 were something more subtantially engineered damaged as well? Seems there is a desire to keep the 6 scale levels (0-5) but limit the rating that can be assigned based on the traditional damage indicators - and this in essence means the entire tornado database pre-dating these new assessment techniques are now all suspect. Sure - they were already suspect before - but at least there was some consistency in how the database was formed. Currently a rather random assortment of assessment techniques are in play at various offices - some using the new indicators, some the old, some reluctant to call in the QRTs, all leading to a database that is probably even less useful than what we had before. Sure - in 30 years, this new rating method could result in more relaible estimates of the frequency of extreme wind events, but why does the historical database need to be tossed out to get there? It doesn't imo if we simply adjust the winds down to match the old F-scale system damage indicators and open up the top end.

Glen
 
Glen,

That would be fine, except the "old" F-scale still says that a well-built home that is wiped clean is F5. Period. However, it's been shown that a home can be wiped clean (thus be F5 damage) with a tornado that has winds of "only" 150mph. Or 300mph. So now what? If an F5 tornado could be either 150mph or 300mph, that tells us little about the intensity of the tornado. Of course, there is ambiguity in assessing exactly what constitutes a "well-built" house, and this has been more apparent in the past 5 years (which partially explains why we haven't seen an F5 since 1999 IMO).

Maybe we could shift the old F-scale winds down substantially. However, that still leaves relatively few damage indicators. How do NWSFOs know what tree damage, or gas station canopy damage, was likely produced by what intensity of winds? The F-scale description says very little about this. Without these other damage indicators outlined, I'd think that there would be a lot of ambiguity. So, let's add more damage indicators, and consult 'experts' as to what range of wind speeds would be most likely to produce certain levels of damage to certain objects. This way, an NWS employee can take a sheet, go out to a damage area, and begin to assess non-standard damage (non-standard being non-'well-built' homes, trees, large warehouses, etc). Because the intensity and type of damage is well outlined (compared to the previous, F-scale), objectivity should be easier to attain. Well, we've basically just arrived at the EF-scale. An outline of new types of damage, with distinct levels of damage, assigned to probable wind speeds.

The tornado climatology database is very important to sustain, as you note. Noting trends in tornado intensities is difficult if the scale on which the tornadoes are rated is changed. We saw this in the 1970s, when a bunch of grad students and others used newspaper clippings and other evidence to rate tornadoes from the 50s and 60s. Looking at trends, you can see curious changes that occurred in number and apparent intensity of tornadoes after the 1970s. Of course, it's unlikely that the actual numbers and intensities have that changed much in the past 40 years... So yes, climo does have importance. However, do we stay course with a scale that isn't entirely descriptive? Or do we transition to a scale which leaves less room for ambiguity in regards to the actual intensity of a particular tornado? What's the best course of action in the long-term? I maintain that the more detailed assessment scale will produce the most realistic determination of tornado intensities, and thus is in the best interest of the scientific community in the long term. Yes, again, the climo database will likely see a discontinuity next year when the EF-scale goes into practice (actually, it's only a discontinuity if EF-rated tornadoes are compared in number to F-rated tornadoes), but I have to think that's all in the best interest of the community when the goal is to accurately and consistently rate tornadoes as close to their actual intensities as is currently possible.

Do we continue with an imperfect scale in the name of climatology, or do we refine the scale to more accurately reflect reality, but reduce the validity of the climatology? I vote for the later. IMO, scientific accuracy in the form of an enhanced, more detailed tornado intensity rating system is more important then maintaining a flawed system in the name of climo. The EF scale is not perfect, but I think it's benefits outweight it's negative consequences.
 
I hear your point Jeff. If a tornado that levels a city is only going to be F3 or EF3 than fine, it is just a number. There may be some scientific value there but the number is meaningless when comparing the new tornado climate record from the one from the historic one. This is my primary concern and Doswell's rant takes the same view. What real value is being added to the climatology with the increased scrutiny of damaged homes and a new rating scale anyway? F4 and F5 tornadoes were already rare and now they are nearly extinct. We are losing the bench mark of reasonable sample size that sets some tornadoes apart from others. Is this what we really want?

Some global warming advocates have proposed that tornadoes are becoming more widespread and damaging without factoring in that we have much better detection rate than we did just 20 years ago and we have more tornado fodder out there. Remember Al Gore's rant after May 3, 1999? I've also read some of the the extreme opposite twisting of data where the non believers in global warming have charts of decreasing numbers of F2+ tornadoes which is partially true, but, they fail to point out that 1970s F2 tornadoes were generally overrated. Now we will have decreasing numbers of F4 tornadoes and no F5 tornadoes. Hey, tornadoes are getting weaker! Go tell Congress, rest assured, that we can keep pumping CO2 in the atmosphere becuase storms are getting weaker.

We are making an already imperfect climatology even more imperfect. I'll try and leave this topic alone now. It gets me fired up as my thesis deals with the F-scale.
 
Alex,

It is of less scientific relevance to base every tornado on the level of damage without any regard to whether a set of wind speeds were really required to produce that damage. If that's the case, then just say that any structure that is wiped clean is F5. A small barn wiped clean? F5. A portapotty wiped clean? F5. If F5 represents that whatever was standing is no longer present, than use that. You'll notice, however, that the scale would then serve almost no scientific value at all.

We currently imply that the F-scale should be used to rate the strength of the tornado. Yes, we know that there have been violent tornadoes in fields that don't hit anything. In the past, per the F-scale, these tornadoes technically should not have received anything but F0, since no damage was produced. The new EF-scale at least provides guidance as to damage to trees, signs, etc. You are correct, we will never really know what the EXACT wind speeds in a particular tornado are. However, isn't it better to try and explain that certain damage to hardwood trees would be most likely to have been produced by winds speeds between xxx and yyy? Or that, unlike what we've thought in the past, 300 mph winds are NOT needed to completely wipe a house clean. In the past, the La Plata tornado would have been F5 (and it was preliminarily rated that). However, we know that wind speeds in that tornado probably were NOT >260mph (F5-level), at least as evidenced by the damage produced. So, you are saying that we should have still rated that tornado as F5? What scientific value does that serve? It tells us nothing about the actual intensity of the tornado.

We know the old wind speeds in the F-scale were too high in some cases. Should we not use this information to better the intensity rating scale used for tornadoes? Should we continue with what we have, ignoring research and studies that have shown some wind speeds are grossly overestimated? Or should we just throw out all wind speed ratings attached to the damage scale, thereby making the scale less scientifically relevant in regards to assessing the intensity of tornadoes?

LOL I'll stop posting here, since I don't want to hog the thread.
 
In the past, so many tornadoes were rated by looking at photographs
of damages, the Super Outbreak if you ever read Storm Data, had
no F-Scale Ratings assigned to them. Remember the F-Scale was
devised in 1971. Around 1980 is when the NWS started to verify warnings,
some offices did a better job than others in surveying tornado damage.
Hopefully the new EF scale, will be more accurate than the current F-Scale.

1950-1959 13 F-5 Tornadoes
1960-1969 11 F-5 Tornadoes
1970-1979 14 F-5 Tornadoes
1980-1989 03 F-5 Tornadoes
1990-1999 10 F-5 Tornadoes
2000-2005 00 F-5 Tornadoes

1950-1979 38 F-5 Tornadoes
1980-2005 13 F-5 Tornadoes

Mike
 
As I stated before on the other EF thread:

I'm part of the team helping develop NWS training (via WDTB) for the new EF scale. In a recent meeting with the lead scientists who helped develop the EF scale, we discussed the possibility of adding new damage indicators (DI), and higher degrees of damage (DOD) for some of the existing DIs. This includes the possibility of adding a DOD for a well-built well-anchored single/double family residence being swept off a foundation (with the usual caveats - no "sliders", duration of wind, debris from other structures, etc). The discussion is in light of some of the concerns being discussed in this forum.
 
I wonder if a part of this may be the influence of insurance companies on some members of the QRT. Someone here mentioned that Tim Marshall of Haag Engineering assisted in the survey of the Westminster tornado. Well, I heard a story on CNN awhile back, and I found its transcript:

http://edition.cnn.com/TRANSCRIPTS/0604/17/lt.01.html

Haag Engineering works for State Farm Insurance in disaster assessment. I wonder if lower F-scale ratings are used by insurance companies as an 'out' on covering what they are obligated to cover, i.e. the companies would refuse to fully pay for completely leveling by and F3 because a lower rating on a house completely flattened would indicate poor construction. Here is another article on Haag and the OKC tornado:

http://www.normantranscript.com/localnews/..._106014529.html

This sort of situation also came up in Hurricane Katrina. An article on that situation follows:

http://news.yahoo.com/s/ap/katrina_insurance

It's also interesting, IMO, how Katrina was later downgraded to cat 3, with a pressure 10 mb lower than any other cat 3 on record. It just makes me wonder if the ratings for both tornadoes and hurricanes are used by the insurance companies when determining amount of payment, and, if so, they are contaminating, via the QRT/NWS, the rating of tornadoes today.
 
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