Super Tornadoes

[Skip Talbot]

No, a 500 mph tornado cannot happen. A 5 mile wide tornado cannot happen.

Source needed.

You don't want to say cannot or impossible when referring to phenomena of which we have a poor understanding. We've been studying tornadoes for only a handful of years, and we only have detailed data sets from a handful of tornadoes. The bounds to what is and what is not possible are unknown. Perhaps it's possible that winds greater than 300, 400, or 500 mph exist at small scales in the most intense subvortices of large tornadoes. Perhaps another extraordinary event can create the conditions necessary to produce a tornado that far exceeds what we've observed. A caldera eruption might create the astronomic instability and wind shear needed to produce an incredibly large and powerful tornado, something along the lines of a volcanic waterspout magnified by about 1000.

 

[rdale]

Source needed.

I disagree... I think a source is needed to prove a 500mph 5 mile wide tornado is possible.

Also I do know of meteorologists and storm chasers who DO use the term "super tornado" when explaining them and talking about

You have two very different sets of users there... There are storm chasers who call every tornado a wedge. Doesn't make them a wedge.

The only meteorologist who I've heard use the term "super tornado" is one on TV who misunderstood Wurman's AMS paper.

But either way - hearing people use the term doesn't make it an actual scientific term.

them b/c they recognize their obvious existence.

As Skip noted - source needed. You cannot read through all of this thread and say supertornadoes OBVIOUSLY exist?

 

[DNewman]

Source needed.

You don't want to say cannot or impossible when referring to phenomena of which we have a poor understanding. We've been studying tornadoes for only a handful of years, and we only have detailed data sets from a handful of tornadoes. The bounds to what is and what is not possible are unknown. Perhaps it's possible that winds greater than 300, 400, or 500 mph exist at small scales in the most intense subvortices of large tornadoes. Perhaps another extraordinary event can create the conditions necessary to produce a tornado that far exceeds what we've observed. A caldera eruption might create the astronomic instability and wind shear needed to produce an incredibly large and powerful tornado, something along the lines of a volcanic waterspout magnified by about 1000.

Gud to know I'm not the only one. A caldera eruption... That's interesting.

 

[Shawn Schuman]

I think we're missing the point here. Claiming that such a tornado cannot possibly happen, at least to my mind, is an untenable position. "Never" and "always" are words that ought to be used with great care. What I think we can say is that, given our current knowledge of the atmosphere and weather systems and so on, it's extraordinarily unlikely that you'll ever see such a thing. It may be theoretically possible, but it's also theoretically possible that I'll simultaneously win the lottery and hook up with Scarlett Johansson tomorrow.

..I'll let you know how that goes.

As for the term "super tornado," some people may use it but it doesn't have any concrete meaning in the way that, say, "violent" tornado (F4+) does. You have to understand that most of the stuff you see on television or elsewhere in the media is hyperbolic, to say the least. You started this thread because you wanted to know what is and isn't possible in the real world, right? Well, we're telling you. A "super tornado" doesn't exist as a scientific concept, and I don't foresee any need for such a term in the future.

 

[DNewman]

I think we're missing the point here. Claiming that such a tornado cannot possibly happen, at least to my mind, is an untenable position. "Never" and "always" are words that ought to be used with great care.It may be theoretically possible, but it's also theoretically possible that I'll simultaneously win the lottery and hook up with Scarlett Johansson tomorrow.

Point well taken Shawn.


..I'll let you know how that goes.

As for the term "super tornado," some people may use it but it doesn't have any concrete meaning in the way that, say, "violent" tornado (F4+) does. You have to understand that most of the stuff you see on television or elsewhere in the media is hyperbolic, to say the least

In some sense I guess it wasn't exactly a good idea saying"super tornado" on media.

 

[rdale]

In some sense I guess it wasn't exactly a good idea saying"super tornado" on media.

It was a very good idea... Media gets money only when people watch. If a TV meteorologist declares his area is the only one to ever experience a "Super Tornado" the consultants love it and ask him to do it more. Obviously he doesn't care whether or not it is scientific or remotely accurate, he's just there to increase his viewer count.

 

[Jeff Snyder]

There is tornado-scale modeling work from Lewellen (and Lewellen) and others that support the notion that 500 mph winds (and, actually, winds above Mach 1) *are* possible in tornadoes. Such extreme winds are likely to occur in the vertical, rather than the horizontal, and thus are/would be exceptionally difficult to measure. In addition, they would be limited in time and space. As such, to measure these, we'd need vertically-oriented sensors with extremely high temporal and spatial resolution.

https://ams.confex.com/ams/pdfpapers/46933.pdf -- Transonic velocities in tornadoes? - W. Steve Lewellen, West Virginia University, Morgantown, WV; and J. Xia and D. C. Lewellen

http://journals.ametsoc.org/doi/full/10.1175/1520-0469(2003)060<2820:IOMNOT>2.0.CO;2 --Influence of Mach Number on Tornado Corner Flow Dynamics - J. Xia,

* W. S. Lewellen, and D. C. Lewellen

http://journals.ametsoc.org/doi/full/10.1175/JAS3966.1 --Near-Surface Vortex Intensification through Corner Flow Collapse - D. C. Lewellen and W. S. Lewellen

Since I was cruising through Lewellen and Lewellen's work, I figured I'd point out this paper that may prove interesting to some STers:
http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2686.1 -Effects of Finescale Debris on Near-Surface Tornado Dynamics - D. C. Lewellen, Baiyun Gong, and W. S. Lewellen

It is remarkable to me that we've been fortunate enough to have had mobile radars sample more than a couple violent tornadoes this past May (Rozel, Carney, Shawnee, Bennington, El Reno, etc.) . We'll have more of our RaXPol observations from 5/31 available to view sometime soon hopefully.

 

[Shawn Schuman]

If this is something you're really interested in, and from your profile and your enthusiasm it sounds like you are, maybe do some research on real events? You could even start a blog and write about them. That's what I do, and it's been a really fascinating and educational experience. Plus, the more you learn about past events, the more you understand what's possible. If path width is what you're interested in, here are a few of the more interesting ones off the top of my head:

February 19, 1884: Waleska, GA
May 17, 1896: Seneca, KS
April 24, 1908: Amite, LA
April 9, 1947: Woodward, OK
June 9, 1971: Gruver, TX (the infamous "Sunray" day)
March 28, 1984: Marlboro County, SC
May 31, 1985: Moshannon State Forest, PA
May 3, 1999: Mulhall, OK
May 22, 2004: Hallam, NE
May 4, 2007: Trousdale, KS

 

[Shawn Schuman]

There is tornado-scale modeling work from Lewellen (and Lewellen) and others that support the notion that 500 mph winds (and, actually, winds above Mach 1) *are* possible in tornadoes. Such extreme winds are likely to occur in the vertical, rather than the horizontal, and thus are/would be exceptionally difficult to measure. In addition, they would be limited in time and space. As such, to measure these, we'd need vertically-oriented sensors with extremely high temporal and spatial resolution.

https://ams.confex.com/ams/pdfpapers/46933.pdf -- Transonic velocities in tornadoes? - W. Steve Lewellen, West Virginia University, Morgantown, WV; and J. Xia and D. C. Lewellen

http://journals.ametsoc.org/doi/full/10.1175/1520-0469(2003)060<2820:IOMNOT>2.0.CO;2 --Influence of Mach Number on Tornado Corner Flow Dynamics - J. Xia,

* W. S. Lewellen, and D. C. Lewellen

http://journals.ametsoc.org/doi/full/10.1175/JAS3966.1 --Near-Surface Vortex Intensification through Corner Flow Collapse - D. C. Lewellen and W. S. Lewellen

Since I was cruising through Lewellen and Lewellen's work, I figured I'd point out this paper that may prove interesting to some STers:
http://journals.ametsoc.org/doi/abs/10.1175/2008JAS2686.1 -Effects of Finescale Debris on Near-Surface Tornado Dynamics - D. C. Lewellen, Baiyun Gong, and W. S. Lewellen

It is remarkable to me that we've been fortunate enough to have had mobile radars sample more than a couple violent tornadoes this past May (Rozel, Carney, Shawnee, Bennington, El Reno, etc.) . We'll have more of our RaXPol observations from 5/31 available to view sometime soon hopefully.

I've come across Lewellen's papers before and found them very interesting, but don't really know what to make of them in real-world terms. I wonder how such an extremely high-velocity instantaneous or near-instantaneous gust would relate to the standard three-second gust in terms of damage potential, assuming it were even close enough to the surface to cause damage.

Also, I thought the Carney wedge was extremely impressive. It had some of the most violent motion I've ever seen. It's amazing that such a slow season as far as total tornado numbers has produced so many opportunities to observe high-end tornadoes.

 

[DNewman]

Thanks for the helpful links, I like the research.
Isn't Mach 1 like supersonic speed at the speed of sound?

 

[DNewman]

I've come across Lewellen's papers before and found them very interesting, but don't really know what to make of them in real-world terms. I wonder how such an extremely high-velocity instantaneous or near-instantaneous gust would relate to the standard three-second gust in terms of damage potential, assuming it were even close enough to the surface to cause damage.

Also, I thought the Carney wedge was extremely impressive. It had some of the most violent motion I've ever seen. It's amazing that such a slow season as far as total tornado numbers has produced so many opportunities to observe high-end tornadoes.

Really appreciate the info Shawn, ill give that a try definitely.

 

[Shawn Schuman]

Thanks for the helpful links, I like the research.
Isn't Mach 1 like supersonic speed at the speed of sound?

Yes. It's ~761 mph given average conditions at sea level.

 

[DNewman]

Yes. It's ~761 mph given average conditions at sea level.

Oh ok 761,that's the speed of sound I believe.

 

[Jeff Snyder]

I've come across Lewellen's papers before and found them very interesting, but don't really know what to make of them in real-world terms. I wonder how such an extremely high-velocity instantaneous or near-instantaneous gust would relate to the standard three-second gust in terms of damage potential, assuming it were even close enough to the surface to cause damage.

Yeah, there's still the problem with relating everything to the 3-s average wind speed/gust used by the EF scale. The models, however, do produce some very realistic structures. For example, check out this simulation of ground swirl marks produced by extremely high resolution tornado-scale simulations:

https://ams.confex.com/ams/25SLS/webprogram/Paper175683.html Taxonomy and analysis of tornado surface marks - . I. Zimmerman, West Virginia Univ., Morgantown, WV; and D. C. Lewellen

Also, I thought the Carney wedge was extremely impressive. It had some of the most violent motion I've ever seen. It's amazing that such a slow season as far as total tornado numbers has produced so many opportunities to observe high-end tornadoes.

There's a couple good chaser videos on YouTube that show extremely impression winds / accelerations within the tornado -- up there with some of the strongest I've seen in video. Of course, there wasn't always a lot of condensation, dust, or other things that can "mask" the higher winds (the edge of the condensation funnel in the El Reno tornado, at times, didn't look very impressive, but it the opaque condensation was making invisible the extraordinarily strong winds within it). I think our radar-measured max winds in the Carney tornado were on the order of 85+ m/s, and the geometry wasn't very good for measuring the strongest winds. Similar to El Reno, the strongest winds were in sparsely-populated, open country well removed from any meaningful structures. As such, the EF scale rating process issues are similar, though the difference between radar-measured winds and the EF-scale rating for the Carney tornado is much smaller.

 

[Jeff Duda]

I disagree... I think a source is needed to prove a 500mph 5 mile wide tornado is possible.

Here are some additional back-of-the-envelope calculations:

Using a simplified form of the momentum equations for geostrophic wind reveals a pressure gradient of 2.23 x 10^-4 mb/m is required to sustain 500 mph geostrophic winds. Scaling that - that's like 2.23 mb over 10 km. (see edit below)

Using information on the 100-mb-pressure-drop measurement by the late Tim Samaras from the 24 June 2003 Manchester, SD tornado and applying a time-to-space conversion (assuming a steady state tornado over a 5-second period with movement speed of 35-70 mph) reveals a localized horizontal pressure gradient of O(1-10 mb/m) at the most intense part of the tornado. (image source: http://www.crh.noaa.gov/images/fsd/events/tor2003jun24/samaras/samaras_fig4.gif)

Of course I am using simplified assumptions (neglecting friction for one) which technically invalidate the specific values I obtained, but considering that the estimated pressure gradient from an observed event is FOUR orders of magnitude higher than the gradient needed to produce straight line 500 mph winds in the relative absence of friction, I would again reaffirm what I said in my first post that it is not physically impossible. Improbable for sure, but not impossible.

EDIT: I'm going to update this for the much more applicable cyclostrophic flow, a balance that concerns turning and neglects the Coriolis force. This balance reveals that a pressure gradient of O(10^-2 mb/m) is required to generate such winds in a 5 mile radius. Friction is still neglected, but we're also still two orders of magnitude smaller than the estimated horizontal pressure gradient from the Manchester data.