Where have all the violent tornadoes gone?

I have noticed that there have been no violent tornadoes (i.e. F4/F5) this year (correct me if I'm wrong) and if there were it must have only been one or two. Despite all these recent "outbreaks" it would seem that none have produced any violent tornadoes.

Thoughts?
 
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I think we would have seen more (or at least one) yesterday (and other days) had we be able to get 64-67+F dewpoints into the main risk area. Looking at surface observations, Tds yesterday were largely in the 59-62F range, though there were occassional 63-64F obs (there were some 66-68F Td obs, but those were in outflow, where we tend to expect cooler, more moist conditions).

Personally, by afternoon, I don't think I've seen a setup this year that really looked like it would support a supercell with F4-F5 tornadoes (don't get me wrong, I'm not surprised by the plethora of F3 tornadoes we've had, since the low-level shear present on several of the synoptically-evident events was quite intense). 3/12 was close I suppose, as was 4/2... I think being on the low end of true deep, Gulf moisture has been a prohibiting factor thus far. Of course, everything tends to tie into everything else... In the Plains, storms have been fighting the strong shear in rather marginal CAPE and dewpoint environments (sometime yielding relatively high LCLs). Yesterday looked pretty good, but I wonder what the CAPE really was in northern MS, northern AL, and southern TN. We just need to wait until we get widespread >64f dewpoints in the warm sector and widespread >2500 j/kg CAPE, IMO... Yes, there have been violent tornadoes in lesser thermodynamic conditions (i.e. per this paper, the 4-16-98 TN F5 was in an environment of ~1600 j/kg CAPE), but it seems that the "big gun" days (e.g. 5/4/03, 5/3/99, 6/24/03, 7/13/04, etc) have >2000-2500j/kg mlCAPE.

Of course, maybe it's just chance... Perhaps the times when a tornado had winds capable of creating F4 or F5 damage occurred when the tornado was away from any structures (i.e. in a field or forest). Or, perhaps storm-scale processes that we can't really analyze or observe prevented violent tornadoes. Add in the recent 'discoveries' / realizations that >210mph winds are not always required to destroy a house (e.g. Marshall's work on the La Plata tornado showed that ill-anchored houses that were initially marked as F5 damage were actually the result of an F2-F3-level tornado), and you see a decrease in the number of violent tornadoes.

EDIT: Note that damage assesssments from yesterday's tornadoes are just beginning, so there may learn that there was a violent tornado yesterday.
 
Alex, there have been two F4 tornadoes in 2005 and 2006 thus far, in Hopkins County, KY on 11/15/05, and Monroe County, Missouri on 3/12/06. I agree survey teams seem to have tightened up on the ratings recently. I don't see what was so much more destructive about those tornadoes compared to, say, Stoughton, Evansville or Caruthersville.

The problem with this IMO is that rating so many tornadoes at F3 implies that they were ALL of equal strength and impact, which is obviously not true but a person reads the record books and that's all they see is the one rating. Hopefully the EF-scale will help clear some of this up but in the meantime we have to make do with the original scale.
 
Some images just north of Nashville definately support an F4 rating for that tornado. There were some larger homes that were completely leveled (no walls standing). If that tornado only gets a "strong" F3 than I have lost all faith in the ratings system.
 
Some images just north of Nashville definately support an F4 rating for that tornado. There were some larger homes that were completely leveled (no walls standing). If that tornado only gets a "strong" F3 than I have lost all faith in the ratings system. [/b]

Well, the final assessment from the tornado near Gallatin isn't in yet, but the very prelim report noted F3 damage. In addition, there was damage near Goodlettsville that was either the same tornado that hit Gallatin or was an earlier tornado (the PNS makes it sound like it was the same tornado, with the use of "the tornado continued on", although they do say the track was 1.1 miles long, much shorter than the distance to Gallatin)...

THE FINAL TORNADO THAT HIT DAVIDSON COUNTY IN GOODLETTSVILLE WAS RATED AS AN F3 (158-206 MPH). THE TORNADO STRUCK AT 2:10 PM CDT AND HAD A PATH LENGTH OF 1.1 MILES AND A PATH WIDTH OF ABOUT 1/2 MILE. A CHURCH LOST THE ENTIRE FRONT SECTION...EXPOSING BENT STEEL BEAMS. A RESIDENTIAL HOME IN GOODLETTSVILLE ON BELL STREET WAS COMPLETELY BLOWN OFF ITS FOUNDATION AND DEMOLISHED. NUMEROUS HOMES HAD ROOF DAMAGE.[/b]
--> Damage Assessment

So, the house must have been a 'slider'. There's another report that sounds F4, but was given F3:
<div class='quotetop'>QUOTE("OHX NWSFO")</div>
THE TORNADO IN DICKSON COUNTY TOUCHED DOWN ON MAPLE VALLEY ROAD IN
NORTHERN DICKSON COUNTY AS AN F2 TORNADO (113-157 MPH) AT 1:30 PM
CDT. THREE MOBILE HOMES WERE LEVELED AND DEMOLISHED. NUMEROUS TREES
WERE UPROOTED AND SNAPPED. THE TORNADO PRESUMABLY CARRIED A TRUCK
UPON A UTILITY POLE, WHERE IT LEFT A WINDOW GASKET ON TOP OF THE
POLE. THE TORNADO CONTINUED ALONG HIGHWAY 49 AND REACHED BELLSBURG
AT AS AN F3 (158-206 MPH). A ONE STORY BRICK HOME WAS DEMOLISHED.
THERE WERE NO WALLS OR ROOF LEFT STANDING...LEAVING ONLY A HALF
BASEMENT AND GARAGE.
A TRUCK WAS THROWN INTO THE BASEMENT BY THE
TORNADO. THE DRYWALL...FURNITURE...AND APPLIANCES WERE HURLED INTO
THE WOODS AT LEAST 100 YARDS. THE TORNADO ENDED AT THIS LOCATION.[/b]
--> Damage Assessment
 
Some images just north of Nashville definately support an F4 rating for that tornado. There were some larger homes that were completely leveled (no walls standing). If that tornado only gets a "strong" F3 than I have lost all faith in the ratings system.
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I feel exactly the same as you....clearly the damage to well built brick homes in Gallatin meet F4 criteria. I've seen the same type of destruction to large, well constructed brick homes before; near Kennesaw GA (11/22/92), Brandon MS (11/21/92), Rydal, GA (3/27/94), and NW of Madison, MS (11/24/01).....all of which were rated as F4.
 
Justin, I find myself feeling similarly. It just seems that something has changed recently and that the same standards used to rate tornadoes 5 years ago is different than today. I realize the EF Scale revisions on wind speeds will change beginning next year. But even with reduced wind speeds, the amount of damage needed to reach a certain F-level will still be similar. Only the estimated wind speed needed to do that damage has changed. Besides, this is still 2006. The new guidelines are yet to take effect, so we should be rating them the same way we did in say, 1997 or 1998.

I dunno what to make of it. But it seems somewhere, something is up.

Can anyone here tell me what sort of process the local offices must go through to rate F4/F5's these days? I understand that if they suspect anything higher than F3 damage, they have to bring in the team of experts to do further investigation. Does doing this somehow create a big hassle for the local offices? Just curious. If it does, perhaps this may have something to do with it. I could see some of those guys saying "you know, I think this is a minimal F4....but since calling in the special team is going to create a headache for us, let's just call it an upper end F3 and be done with it." I mean these folks are only human and if the new process that came along in 2002 did create a bunch of new hassles for the local offices, I could understand how they might at times "hold back" just a bit. Again, I have no proof whatsoever that such a scenario has actually been playing out. But it is just one theory that crossed my mind. And I have noticed some of the surveys have keyed in on certain aspects of the damage. One of yesterday's tornado surveys in TN I read stressed at one point a particularly interesting piece of damage....where a well constructed home had been leveled and perhaps cleaned of the foundation. Then there was another hint dropped that the preliminary rating was currently strong F3...but that further evaluation was taking place. Basically, the same was said of the April 2 tornado in Marmaduke, AR.

This just all makes we wonder. I don't mean to suggest that there is some sort of vast conspiracy within the NWS to limit the number of tornadoes recorded as violent. That would make no sense whatsoever. But I do wonder if something else is either directly or indirectly having an effect on how some of these tornadoes are rated. I don't think it's just coincidence that we haven't seen an F5 since 1999 and that over the past 5 years, there appears to be a downturn in the number of tornadoes rated F4 as well. IMHO, I don't feel that this is all a result of the weather. As many huge outbreaks of very damaging tornadoes that we have seen in 2002, 2003, 2005 and so far in 2006, it's hard to convince me that not a single F5 was among them, especially considering we seemed to average about 1 per year in the previous decade. Something here just doesn't seem right, but what I don't know. But I will say something has changed. If there has been a change, then that calls into question all the previous ratings assigned over the previous 30 years. It also causes me to have some doubts about the credibility of the F-Scale ratings as a whole. I just want to see some consistency. And if a tornado today does the same damage that an F4/F5 tornado did in the 90's, then it should be given the same rating. Otherwise, they are all meaningless.

Just my opinion.
 
I just returned from the Nashville area after chasing southern Tennessee and northern Alabama Friday. I've got a lot of video and photos to go through but I'll post a quick comment. Lisa Wadlow and I saw the Gallatin-Goodlettsville damage path first hand and witnessed damage that easily qualifies for an F4 rating. Well-built houses in nice neighborhoods leveled in Gallatin, some of brick construction. In Goodlettsville, we found a large metal dumpster deposited at least 1/4 mile away from the damage path in the driveway of a nearby house. In Gallatin we saw a car thrown into a driveway of house just outside the damage path. There were gouge marks in the pavement on the street and in the yard where the car impacted as it was tossed/rolled at least 200 feet (we couldn't find evidence of where the car was initially). I'll post a few pictures soon.
 
Dan, if that is the case, then perhaps that particular tornado will end up being rated F4 afterall. They are still working on that one and have yet to make a final determination. All of the other intense tornado paths have already been rated. The fact that this is the only remaining intense tornado track (in the Gallatin area) to not be rated, makes me think they might be debating F3 vs F4.

But, if you say it's F4 (with as many storm paths as you've seen), then it's an F4. That damage you describe certainly sounds like lower end F4 to me.
 
This is a very interesting thread to read. I am a hurricane chaser-- my interest in severe local weather is more casual-- but tropical weather watchers are having these exact same discussions Re: recent trends in the intensity ratings of landfalling hurricanes.

The National Hurricane Center over the last few years seems to have gotten more stringent with its rating requirements. For example, Katrina's final rating for its LA landfall was lowered to Cat 3 (despite its extremely low 920-mb landfall pressure) because the wind data just didn't support Cat 4. Similarly, Rita was barely rated a Cat 3 for its TX/LA landfall despite a very low central pressure of 937 mb and the complete destruction of several SW LA communities. It seems the NHC is making an extra effort to really qualify each rating. As can be expected, these downward adjustments in the ratings of these big "headline storms" have proven very controversial with online bloggers.

The question that arises: if the NHC is using newer, stricter methodology for rating the intensities of modern landfalling hurricanes, how do we compare these modern hurricanes to big historic ones that may have been overestimated? The NHC is currently doing a reanalysis of all USA hurricane landfalls dating back to 1851. It is widely expected that the estimated intensities of some big, historic storms may be adjusted downward based on the new knowledge and methodologies. The benefit to this will be a consistent standard-- and cleaner comparisons between modern and historic events.

Getting back to twisters… If they have, indeed, changed their criteria for rating contemporary tornadoes, I am wondering if they need to do a similar reanalysis of historic tornadoes. Otherwise, there will be no way to meaningfully compare modern and historic events-- no common yardstick, no gold standards.
 
If you notice the survey of the Gallatin tornado, it says that the rating is very preliminary and subject to change. I think Greg Stumpf might know if the expert survey team (forgive me, I can't recall the actual name of it) was deployed to that area.

Two things I will say about the Gallatin tornado:
1. Huge $300,000+ homes being pancaked in most often at least F4 damage (and looks to be in this case), and
2. From the video I've seen of the tornado, it was one of those classic violent tornado structures, with a pretty narrow funnel comprised of tiny but powerful multiple vorticies, such as the West Lafayette F4 tornado of 3/20/76, the Saylor Park tornado (F5) of 4/3/74, and the Granite Falls, MN, tornado (F4) in July 2000.
 
Simple: Compare the Tennessee damage to the rated F4 damage in La Plata, MD. No question that the Tennessee twister did more damage. Those were $500,000 homes that were piles of debris. Not talking about a ranch house that slid into a small ravine.
 
I'm not saying the Gallatin tornado will not end up being rated F4 or F5 (no way I can know that from here), but I'd strongly caution against using pictures of homes to make broad distant judgments on the wind speeds and F-scale damage of a tornado. There are many damage indicators to look at, such as ground marks/scouring, trees and vegetation, utility poles, fences, surrounding structures and so on. For myself, I will let the experts who have done considerable training on wind damage assessment AND have taken the time to take considerable notes from the actual scene assign the ratings...instead of second guessing them with only small pieces of the puzzle from hundreds of miles away.
 
I'm not saying the Gallatin tornado will not end up being rated F4 or F5 (no way I can know that from here), but I'd strongly caution against using pictures of homes to make broad distant judgments on the wind speeds and F-scale damage of a tornado. There are many damage indicators to look at, such as ground marks/scouring, trees and vegetation, utility poles, fences, surrounding structures and so on. For myself, I will let the experts who have done considerable training on wind damage assessment AND have taken the time to take considerable notes from the actual scene assign the ratings...instead of second guessing them with only small pieces of the puzzle from hundreds of miles away.
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It's interesting you say that, because I was just reading Tim Marshall's analysis of the La Plata, MD, tornado (2002), which had been initially over-rated as an F5.

In the report, he makes exactly your point-- that all of the clues matter, not just the house itself. They found examples of homes completely blown off their foundations with 1) roofs still intact, 2) mailboxes still standing, and 3) vegetation on the lawns mostly unscathed. Such observations led them to conclude that the construction was largely responsible for some of these failures, and that some of these homes actually slid off their foundations from winds as low as 100 mph!

The report is very interesting: http://ams.confex.com/ams/pdfpapers/53280.pdf
 
Yep, that's what I was thinking of, Josh. Local building codes and practices have a lot more to do with the structural soundness of a home than the price tag. I know there are some $500K+homes built today with all sorts of safety corners cut that might make them disintegrate in an F3 tornado, while a 1960 home worth $75K today with hurricane straps and strong roof<->walls<->foundation anchoring might withstand the same tornado. I'm sure all that will be factored into the final F scale rating, along with the other nearby damage indicators. To address the broader point, a lot of these things were learned and documented in the Moore and La Plata damage surveys, so I think we're seeing a lot more (healthy) skepticism about the initial tendency to automatically rate high on tornadoes that blow away homes.
 
Violent tornadoes haven't gone anywhere. The ratings have.
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If that is the case-- and the ratings standards are, indeed, changing-- I imagine that is going to make comparisons of contemporary and historic events difficult-- unless the historic events are reanalyzed according to the contemporary standards.
 
Violent tornadoes haven't gone anywhere. The ratings have.
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Exactly.

It's hard for me to believe some of those tornadoes were only rated F3, when we had an F3 here in MI back in 1997 that did half the damage. The tornado intensity hasn't decreased at all, it's the rediculously strict rating methods that are now being put in place. I am willing to bet that we won't see an F5 in at least the next several years ... if at all. It just seems like there's always something to blame (i.e. it was a slider, there was wind tunneling, it was being pelted by debris, the tornado was moving too slow, etc.).
 
It's interesting you say that, because I was just reading Tim Marshall's analysis of the La Plata, MD, tornado (2002), which had been initially over-rated as an F5.

In the report, he makes exactly your point-- that all of the clues matter, not just the house itself. They found examples of homes completely blown off their foundations with 1) roofs still intact, 2) mailboxes still standing, and 3) vegetation on the lawns mostly unscathed. Such observations led them to conclude that the construction was largely responsible for some of these failures, and that some of these homes actually slid off their foundations from winds as low as 100 mph!

The report is very interesting: http://ams.confex.com/ams/pdfpapers/53280.pdf [/b]

Tim Marshall did a presentation on the La Plata tornado at the NSWW'03, which can be viewed online at http://www.nssl.noaa.gov/nsww2003/talks/Tim_Marshall.htm

I've seen another one of his presentations online, which noted that some of the houses in Moore OK on 5-3-99 were "completely destroyed" with winds of only ~140-160mph. If the house is gone, but the mailbox is standing and trees in the front yard are still there, that gives you a clue.
 
The tornado intensity hasn't decreased at all, it's the rediculously strict rating methods that are now being put in place. I am willing to bet that we won't see an F5 in at least the next several years ... if at all. It just seems like there's always something to blame (i.e. it was a slider, there was wind tunneling, it was being pelted by debris, the tornado was moving too slow, etc.).
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See my post above. I feel the exact same thing has been occurring with hurricane landfall intensities-- they seem to be getting more strict with the higher ratings.

Tim Marshall did a presentation on the La Plata tornado at the NSWW'03, which can be viewed online at http://www.nssl.noaa.gov/nsww2003/talks/Tim_Marshall.htm

I've seen another one of his presentations online, which noted that some of the houses in Moore OK on 5-3-99 were "completely destroyed" with winds of only ~140-160mph. If the house is gone, but the mailbox is standing and trees in the front yard are still there, that gives you a clue.
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Hey Jeff, thanks for sharing that-- it's a cool presentation. Have they concluded that the Moore event was overestimated as well?
 
I guess the real question is, how rare are (truly) violent tornadoes?

Personally, I like the practice of being more skeptical about F4/F5 ratings, because it distinguishes the fairly strong tornadoes from the doozies that wipe out everything within a 5 house radius.

Gabe
 
I'm not saying the Gallatin tornado will not end up being rated F4 or F5 (no way I can know that from here), but I'd strongly caution against using pictures of homes to make broad distant judgments on the wind speeds and F-scale damage of a tornado. There are many damage indicators to look at, such as ground marks/scouring, trees and vegetation, utility poles, fences, surrounding structures and so on. For myself, I will let the experts who have done considerable training on wind damage assessment AND have taken the time to take considerable notes from the actual scene assign the ratings...instead of second guessing them with only small pieces of the puzzle from hundreds of miles away.
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You and Josh are both correct. A good example of this was one of the F3 tornadoes in Indiana on 11/15/05. I rated the tornado that moved through Shelby County that afternoon, and the worst damage along that path was a great example of exactly what you cite. The home had been swept off the foundation. However, the foundation itself was little more than stacked stones, and no evidence of any significant attachment to the foundation could be found on the walls. Indeed, homes on such foundations are rarely attached to the foundation in any appreciable manner, and as such, are capable of being moved off their foundations by winds of less than 100 mph.

In concert with this, we also found several examples of unharmed vegetation, and a large and strong tree near the remaining front porch which had lost only the top third of the tree. The trunk remained standing tall.

I know some seem to have a chip on their shoulder about this subject, but which is better...continuing to overrate tornadoes, which has likely occurred a great deal in the past, or learning more and rating them as accurately as possible based on everything we know? I know which one is more scientifically responsible.
 
The only changes to the rating system have been the addition of the Quick Response Team, which WFO's much use if they suspect that a tornado caused F4 or F5 damage. The criteria has not changed, the F-Scale has not changed (yet) and the tools meteorologists and engineers use to rate damage has not changed.

From what I can tell looking at PNS's from OHX, they are not done with the Gallatin classification. As Kevin mentioned, it is not always possible to make an accurate determination of the tornado damage rating by looking at images and video. And we should also remember that F4 and F5 tornadoes are still very rare.

Rick
 
Are we attempting to rate the estimated wind speed or are we attempting to rate the damage? Fujita's scale used damage (primarily to homes) to estimate wind speeds and the inherent F-rating. Fujita and just about everyone else realized those wind speeds were far too high given changing constuction styles and engineering studies. Despite this, tornadoes have been generally rated according to the "damage" scale rather than the original "wind" scale. Tornadoes in the 1970s were generally overrated based on today's surveys. A plot of F2 tornadoes reveals of decreasing trend after that decade. Most tornadoes prior to 1976 were rated post mortem via newspaper clippings. Now just about all suspected F3+ damage brings in the expert survey crew looking at supports, nails, beams, vegetation, etc. Comparing today's tornado intensities (or should I say survey results) to those in the 1970's should yield inconsitent results. While not quite apples to oranges, perhaps green apples to red apples. The damage is similar but it is now looked upon in a different way. I don't think the violent tornadoes have gone anywhere... they have simply been downgraded based on differing perspectives and new information.

I still think that TN tornado is an F4. It had the classic core of hellish winds that leveled homes with gradually less damage away from the center. I don't care what the wind speed was as the damage is indicative of F4 on the old rating system. It is just not practical to measure every tornado's wind speed directly which is why we have the damage scale in the first place

Some folks here are noting mail boxes and vegetaion with various tornadoes. You can look at a point source of damage thinking you are getting the big picture and still miss the big picture. I have seen F3 and F4 surveyed damage where a mailbox still stands. This may be due to the box or shrub being low to the ground or missed by a subvortex
 
Are we attempting to rate the estimated wind speed or are we attempting to rate the damage? Fujita's scale used damage (primarily to homes) to estimate wind speeds and the inherent F-rating. Fujita and just about everyone else realized those wind speeds were far too high given changing constuction styles and engineering studies. Despite this, tornadoes have been generally rated according to the "damage" scale rather than the original "wind" scale. Tornadoes in the 1970s were generally overrated based on today's surveys. A plot of F2 tornadoes reveals of decreasing trend after that decade. Most tornadoes prior to 1976 were rated post mortem via newspaper clippings. Now just about all suspected F3+ damage brings in the expert survey crew looking at supports, nails, beams, vegetation, etc. Comparing today's tornado intensities (or should I say survey results) to those in the 1970's should yield inconsitent results. While not quite apples to oranges, perhaps green apples to red apples. The damage is similar but it is now looked upon in a different way. I don't think the violent tornadoes have gone anywhere... they have simply been downgraded based on differing perspectives and new information.

I still think that TN tornado is an F4. It had the classic core of hellish winds that leveled homes with gradually less damage away from the center. I don't care what the wind speed was as the damage is indicative of F4 on the old rating system. It is just not practical to measure every tornado's wind speed directly which is why we have the damage scale in the first place

Some folks here are noting mail boxes and vegetaion with various tornadoes. You can look at a point source of damage thinking you are getting the big picture and still miss the big picture. I have seen F3 and F4 surveyed damage where a mailbox still stands. This may be due to the box or shrub being low to the ground or missed by a subvortex
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Not to open a can of giant worms, but weren't there at least one or two mailboxes left from the Jarrell tornado?
 
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