Greensburg/Trousdale tornado 4 miles wide?

[Lanny Dean]

Mods: Feel free to move this if info has been posted elsewhere.

Greensburg.....we say that word and destruction comes to mind.
For anyone who happened to be on that beast knows how big it was, but some of the latest info and data suggest that it might have been bigger than what we thought.
A paper by Less Lemon and our very own, Mike Umscheid has cast new light on the extremes of the Greensburg supercell/tornado(s) and just how big the tornado(s) really were. The paper can be found here: http://ams.confex.com/ams/24SLS/techprogram/paper_141811.htm

Since the Greensburg event, there have been questions as to how the Greensburg tornado "stacked" up against other large tornado events such as the May 3, 1999 Moore/OKC event. This paper goes into detail regarding both events and of real interest to me at least, is the fact that the Greesburg tornado had such a stronger gate to gate across a set diameter: "138 kts and a shear of 237kts or 121.9 m/s across a 2 km diameter." The paper includes some great pictures of the tornado as photographed by Dick M, Mike Scantlin and others and even has a first hand account of the event from ground zero.

This is a must read for anyone who was involved with the event.

 

[Verne Carlson]

Awesome paper, very well written. I'm still going through it but it looks like from Table 1 the widths are in Km not miles so the largest wedge was the Trousdale tornado at 4.1 Km = 2.7 Miles wide. Still pretty amazing size.

This is the first time I've seen the full ground survey layed out on a single map. Pretty amazing! We were on tornado #19 up there by Claflin at around 1-2am. We never saw #20, 21 or 22 - probably because we were approaching from the west and our view was blocked by tornado #19.

A very historic night and one that still sends shivers down my spine...


Edit: The CAPE vs. 0-1 km SRH from Figure 5 - unbelievable how extreme those values were in the environment that night.

 

[Mike Smith]

As usual, Les and Mike do excellent work.

Here is what I take away from this: The implications of the Trousdale or Greensburg tornado spending their entire life in a densely populated city are genuinely frightening. To my knowledge, one of these 'supertornadoes' has never struck a major city.

Take the Trousdale tornado and have it touch down at Will Rogers World Airport in OKC. Then have it reach its maximum strength over downtown OKC and Bricktown and then continue into north OKC. I believe an emergency response would be required on the scale of what is done for hurricanes. I do not believe OKC, STL, DAL, or any other metropolitan area would be able to quickly gear up for a response on that scale.

Keep in mind that with a 2.8 mile wide tornado (Trousdale), I-40 and major streets like Reno would be impassable for more than 3 miles (E-W) and, eyeballing, streets like Broadway would be impassable for a length of more than 4 miles (eyeballing the Trousdale tornado over Mapquest).

Helicopters would be required to get to anywhere close to the core of the damage path. Fire and police stations would be cut off. Think of the downtown FTW damage during their March, 2000 low-end F-3 tornado. Now, put a strong F-5 into (for example) downtown OKC or DAL during the end of the work day.

So, I write this in hopes that appropriate individuals might give this some thought before one of these supertornadoes makes its inevitable appearance in a major city.

 

[Johnathan Brouwer]

What strikes me about the data and the presentations...is what do we call it? A extremely large tornado or a small powerful cyclone?

 

[cdcollura]

Good day all,

Very impressive indeed. Great job for putting this together.

The vortex "hole" is impressive, making this "thing" look like a supercell so large and with a meso so powerful it causes the entire cumulonimbus to take on the structure of a hurricane eyewall to some extent.

The tornado(es), including the Greensburg one, as large as they were, were merely sub vortices going around the huge mesocyclone!

I noticed a similar feature back in 2004 on the May 22 Hallam, NE storm radar (above). This also CLEARLY had a vortex hole in it's radar image, with the large hook removed from it ... Though i'd toss that example up as well.

 

[Lanny Dean]

Awesome paper, very well written. I'm still going through it but it looks like from Table 1 the widths are in Km not miles so the largest wedge was the Trousdale tornado at 4.1 Km = 2.7 Miles wide. Still pretty amazing size.

This is the first time I've seen the full ground survey layed out on a single map. Pretty amazing! We were on tornado #19 up there by Claflin at around 1-2am. We never saw #20, 21 or 22 - probably because we were approaching from the west and our view was blocked by tornado #19.

A very historic night and one that still sends shivers down my spine...


Edit: The CAPE vs. 0-1 km SRH from Figure 5 - unbelievable how extreme those values were in the environment that night.

Verne, you are correct with the measurments being metric, however; Mike and Les raise an amazing question in regards to how wide the tornado was....as you can see with the data from the DDC 88D as well as GrLevel 2 Analyst, it shows a well defined "hole" (for lack of a better word)
nearing 7km (4 miles wide)!!! Both Mike and Less ask the question: is this near ground "hole" the tornado core(TC) or the meso?

As most of you know, I was on this tragic event from the start and after meeting Dick M. and Darrin B. near Coldwater, we all intercepted the storm on 160 HWY between Protection and Sitka. It is interesting to note the time stamps just before and right after near this area and then look at the the "split" of the "three amigos" from the 88D.
Of more interest IMO is the data just before and as the tornado is going through Greensburg and the full occlusion phase.
Great paper....kuddos to Mike and Les.

John Davies also did a wonderful write up on this event which can be found on his website: http://members.cox.net/jondavies6/050407greensburg/050407greensburg.htm

 

[Lanny Dean]

What strikes me about the data and the presentations...is what do we call it? A extremely large tornado or a small powerful cyclone?

Great question!!!! Any thoughts????

 

[Jason Foster]

Hallam, NE 2004 previous record....2.1 miles wide

Good day all,

Very impressive indeed. Great job for putting this together.

The vortex "hole" is impressive, making this "thing" look like a supercell so large and with a meso so powerful it causes the entire cumulonimbus to take on the structure of a hurricane eyewall to some extent.

The tornado(es), including the Greensburg one, as large as they were, were merely sub vortices going around the huge mesocyclone!

I noticed a similar feature back in 2004 on the May 22 Hallam, NE storm radar (above). This also CLEARLY had a vortex hole in it's radar image, with the large hook removed from it ... Though i'd toss that example up as well.

....and I believe the recorded width of Hallam, NE 2004 was the record, before Greensburg, at 2.1 Miles wide. I was with Chris and Jeff G. that season and we witnessed F4 (old scale) damage well away from the Town...that was perpendicular to the path direction.

 

[Bob Hartig]

The authors raise that question of nomenclature--i.e. is it a mesocyclone, a tornado cyclone, or a tornado? What the heck do you call something like that?

They also wisely observe that the atmosphere doesn't give a rip what we call it--it just does what it does, leaving those who study it to try to get their arms around its vagaries. Lemon and Umscheid's paper furnishes a fascinating analysis of an off-the-charts event. And it sets me to thinking about the structure of this storm as being a bit like an onion, with various layers of rotation. At its maximum, the larger-scale rotation was over four miles across with wind speeds of over 100 knots that may have reached the ground. If it did, then in my book as a non-scientist, that fits the textbook definition of a tornado. It's hard for me to even fathom one that size, or even half that size. Yet within it is another, still more intense ring of the onion--the 2.5-mile-wide Mackville/Trousdale tornado, itself a monster of brain-buckling magnitude. And within that are smaller-scale vortices--another layer of the onion, so to speak--while around it, other satellite tornadoes form and dissipate. The "vortex hole" was characterized, as I understand it, by chaos, by intense winds blowing every which way, a huge blender of vorticity.

For me, one simple, practical take-away value is, in a high CAPE/high helicity environment, anything can happen.

 

[Michael O'Keeffe]

That is a great paper! There is no question that, the storm that Greensburg tornado developed from what was an absolute monster. My dad and I were a good 6-7 miles south of the Greensburg tornado and our car was rumbling in the insane inflow winds. 7 miles away!! Below is a video still of the Greensburg tornado just as it was entering town with the structure above it. If the Greensburg tornado was 1.7 miles wide when it entered town just compare it to the meso above it and it is almost mind boggling how big that meso was!

 

[Lanny Dean]

The authors raise that question of nomenclature--i.e. is it a mesocyclone, a tornado cyclone, or a tornado? What the heck do you call something like that?

They also wisely observe that the atmosphere doesn't give a rip what we call it--it just does what it does, leaving those who study it to try to get their arms around its vagaries. Lemon and Umscheid's paper furnishes a fascinating analysis of an off-the-charts event. And it sets me to thinking about the structure of this storm as being a bit like an onion, with various layers of rotation. At its maximum, the larger-scale rotation was over four miles across with wind speeds of over 100 knots that may have reached the ground. If it did, then in my book as a non-scientist, that fits the textbook definition of a tornado. It's hard for me to even fathom one that size, or even half that size. Yet within it is another, still more intense ring of the onion--the 2.8-mile-wide Mackville/Trousdale tornado, itself a monster of brain-buckling magnitude. And within that are smaller-scale vortices--another layer of the onion, so to speak--while around it, other satellite tornadoes form and dissipate. The "vortex hole" was characterized, as I understand it, by chaos, by intense winds blowing every which way, a huge blender of vorticity.

For me, one simple, practical take-away value is, in a high CAPE/high helicity environment, anything can happen.

Bob,
a great anology you use....no question, if indeed those winds in the 4 mile radius were ground level i.e. touching the ground, that is by definition, a tornado no matter which way we slice that onion.

 

[Shane Adams]

When was the width of the second wedge tornado (after Greensburg) widened? And why wasn't it updated in Storm Data?

 

[rdale]

Storm Data is not updated. Ernie Ostuno of NWS GRR found some significant errors (including counting one man dead who was clearly alive) in a tornado outbreak in Michigan a while back, and there was no interest in getting those stats into any database with SPC or NCDC. Article in the EJSSM.

 

[Lanny Dean]

When was the width of the second wedge tornado (after Greensburg) widened? And why wasn't it updated in Storm Data?

Shane, I am not sure exactly when the "changes" happened or if indeed they were "changes" seeing as how they do not always update/upgrade with new info after the fact.

This poses a few new questions though relating to the updated data.

 

[Bob Hartig]

Your question could be understood a couple of ways, Shane.

* If you mean the size of the wedge being expanded beyond 2.5 miles--good question. The paper indicates it was 4.1 km, which figures out to 2.5 miles, not 2.7, as mentioned by one poster. As for the 2.8 figure in my own previous post, that was my error, and I'm glad you caught it. I went back to the paper and double-checked, and will make the correction in my earlier post if I can still edit. The tornado was already of a sensational size and doesn't need to be oversensationalized.

* If you're referring to the 4-mile-wide figure, that's an area of speculation that really is the core of this thread. The paper documents a tornado cyclone 7 km across. That converts to 4.3 miles. And the wind speeds evidently were of tornadic intensity, and may have extended to ground level. Here are some relevant quotes from the paper:

Are we resolving a larger and stronger tornado cyclone than previously reported? Are we actually resolving a very strong and large tornado by KDDC? (This may well be the case)...

To reinforce the statement made earlier in section 3.1, this vortex appears to be on the spatial scale of the mesocyclone, but with mean velocity on the scale of the tornado...

...We estimate actual TC tangential velocity of 74 m s-1 or 144 kts.
This becomes even more amazing when at 0433 the radar resolved core circulation TC at 0.5o has grown to 7 km (3.9 nm) across with a mean tangential velocity of 52 m s-1 or 101 kts!

These statements obviously leave things up for speculation. Did a four-mile-wide tornado actually occur? Looks like the best answer is, very possibly. But at this point, it can't be firmly established. From what I gather, Lemon and Umscheid presently are referring to the circulation as just an extraordinarily intense tornado cyclone.