"Meso-Eyes"

[Terry Tyler]

Ive got a Question about the "Meso-Eyes" or "Tornado Eyes" for lack of a better term. Take a look at the Rapid-Dow radar from 6/5 of this year. You will see on a much higher-resolution of what im talking about.

- http://www.nssl.noaa.gov/projects/vortex2/multimedia/5jun09_loops/fullres/05june-rapiddow-wide.gif


That is higher-resolution stuff then Level3 or 2, but you can see them form on there too. Heres one I saw one in Longview, TX just two days ago. You can see those "Meso-Eyes" displayed at two different times. There have been a few notable examples this year such as the EF-2 Shreveport Tornado. On high-rez radar, you can really see these images come alive. I saved some 2-Panel Screen shots for yall to look at and have a couple other examples of these "Meso-Eyes" from storms earlier this year. Basically, what im talking about is a Rain-Free or Semi-Rain-free hole that takes place where your Hook is. Apparently its Rain wrapping Violently around a circulation, but wraps around so much to the point it leaves a rain-wrapped/rain-free core to either a Wall-Cloud/Meso or the actuall Tornado Itself.


Here is an Example from two days ago of one sitting Just overtop of I-20 S of Longview, TX. Look and see! Thats where the Hook belongs, but where you would normally see it. Instead, you see a shallow 35dBz area surrounded by a 45+dBz area. The thing is, If you look over at the Storm Relative image. You will see the core of the cirulation is right over top of that "Eye".

These holes measured only 0.1-0.3nm in width, so I want to know if these are Wall-Clouds or the Tornadoes Themselves. Here goes another scan of the Same Storm taken just 25mins later. This one shows a Rain-Free Eye with a strong couplet. You can clearly see the rain swirling around that Hole. The question is; Is that the Tornado?

I could only imagine how it Looked on Level2 or Super-Rez. Maybe someone can dig up some shots.

Here is One More Scan from 6/17 of this Year. Youve already seen what im Talking about so tell me what you think. Are these Tornadoes or Wall-Clouds or Nothing?

 

[IAN GIAMMANCO]

The "eye" in the Rapid-Dow imagery is associated with the tornado circulation itself and the weak echo region is typically caused by the centrifuging outward of particles (dirt, water droplets, etc...). It would seem unlikely that the 88-D could actually resolve this feature unless the circulation was extremely close to the radar site. This echo hole associated with the tornado circulation has been commonly observed in research radar data.

I do recall the Shreveport supercell which was very close to the 88-D and you could get a feel for the vortex structure near the tip of the hook, I have a screen capture somewhere on my office machine but can't get to it right now. However the Longview storm a few days ago was a reasonable distance from the 88-D and unlikely that this feature would have been resolved. Although, the 88-D may be able to resolve this feature in the extreme events (e.g. Greensburg), someone else can chime in with more on this as I'm sure there are probably a few more of the significant cases where the 88-D data may have shown some reflection of this.

 

[Mike Smith]

Of course, Greensburg had a huge hole. See Lemon and Umsheid's paper.

 

[Terry Tyler]

Of course, Greensburg had a huge hole. See Lemon and Umsheid's paper.

Thanks, I take it this was the Paper you were talking about, Sure explains alot. Apparently these things do have a Name. Theyre called "Tornado Cyclones" or "Vortex Holes".

- http://ams.confex.com/ams/24SLS/techprogram/paper_141811.htm

 

[Skip Talbot]

I think you're looking more at the mesocyclone/updraft tower in most cases than you are the tornado or even the tornado cyclone. The tornado cyclone is going to be visible in large/violent cases, but in many cases the 88D is looking above the base of the storm unless its really close to the radar site. If you mouse over that hole it should say what altitude the scan is at that point. I know LCL's were really low on the Longview, TX day, 600-800m? On the radar scans these holes are known as BWER's (bounded weak echo regions). They definitely mark the rain free regions of the updraft, and whether the radar is resolving smaller scale features like a tornado cyclone, depends on the size of the storm and the proximity to the radar.

 

[Terry Tyler]

It would seem unlikely that the 88-D could actually resolve this feature unless the circulation was extremely close to the radar site.

The tornado cyclone is going to be visible in large/violent cases, but in many cases the 88D is looking above the base of the storm unless its really close to the radar site......They definitely mark the rain free regions of the updraft, and whether the radar is resolving smaller scale features like a tornado cyclone, depends on the size of the storm and the proximity to the radar.

I saw another one of these features today in NC. After reading your comments, Take a look at this. Is this a TC ?

The radar beam was only 120ft above the ground and 4.9mi from TCLT according to the program. Also, this is from a TDWR and displays much higher resolution output. A tornado was reported with this storm 1mi N of Pawcreek and the image itself looks alot like the one on the doppler on wheels.

Is that the Tornado Cyclone ?

 

[Chad Cowan]

I saw another one of these features today in NC. After reading your comments, Take a look at this. Is this a TC ?


The radar beam was only 120ft above the ground according to the program. Also, this is from a TDWR. A tornado was reported with this storm and it looks alot like the one on the doppler on wheels. Is that the Tornado Cyclone ?

I would say with a fair amount of certainty that the radar beam in this case was sampling the actual tornado.

 

[Jeff Duda]

I don't think that is the actual tornado. I made a measurement based on that image and the circulation is about 1 nmi wide, which would make for a HUGE tornado. Also the lack of strong gate-to-gate shear suggests this is probably just a tight circulation of some kind. It certainly would be close enough and the beam low enough to be in the region of a tornado, however. This is an intriguing image capture, Terry.

In regards to your question, I don't think you can really tell the difference between a tornado and a tornado cyclone on an 88D or TDWR.

 

[MatthewCarman]

Several years back a severe storm was ongoing in western Iowa and Dr. Greg Forbes had the radar up and I could see a donut hole in the storm. Dr. Greg Forbes even called it a donut hole. I think it was in the center of the storm and not with an area of rotation. The hole was so clear there was no clouds even being picked up by reflectivity which made me think the sky was clear there. I thought it was interesting when I saw it.

 

[Mike Smith]

Damage with debris aloft was reported with the cell displayed on the CLT TDWR. See: http://www.spc.noaa.gov/climo/reports/today.html and www.wral.com's story about the storm.

I disagree that tornadoes cannot be seen on TDWR's. They have much higher wind measuring resolution than the WSR-88D's to the extent that we are integrating the TDWRs more tightly into our warning operation.

If a TDWR can resolve a microburst (which they can, I have an article coming out about one in Professional Pilot next month), it can resolve a tornado at close range.

 

[David Goines]

Matt Carman,
Just because there is a hole in the reflectivity at all doesn't mean the sky was clear in the "donut hole". Reflectivity is from precipitation, not clouds. Radar can barely pick up drizzle let alone condensation. If you had a satellite view of the event to confirm the donut hole was truly clear, that's a different story. Sounds like a very unique storm though.
Also, did you look at all of the different elevation scans? Or was this from a composite reflectivity?

 

[Greg Stumpf]

I disagree that tornadoes cannot be seen on TDWR's. They have much higher wind measuring resolution than the WSR-88D's to the extent that we are integrating the TDWRs more tightly into our warning operation.

If a TDWR can resolve a microburst (which they can, I have an article coming out about one in Professional Pilot next month), it can resolve a tornado at close range.

Not exactly...

From: Burgess, D.W., M.A. Magsig, J. Wurman, D.C. Dowell, and Y. Richardson, 2002: Radar Observations of the 3 May 1999 Oklahoma City Tornado. Wea. Forecasting, 17, 456–471.

One salient conclusion made by the authors, "For a broad radar beam straddling the edge of the core, the power-weighted mean velocity would be biased by the slower scatterer speeds in the high reflectivity ring outside the radius of maximum winds. Thus, centrifuging indirectly contributes to further underestimation of the peak wind speeds in the tornado."

This should apply to both TDWR and WSR-88D even though the TDWR azimuthal sampling is 2x better. The radar is not explicitly resolving the tornado vortex, but rather the slower larger debris within the tornado, causing an overestimate of the vortex diameter and an underestimate of the velocities.

 

[Mike Smith]

Greg,

I am very familiar with that paper and used it as recently as a year ago in some work involving Greensburg.

I think you are misinterpreting what I said: If it is resolving rotating debris, it is resolving the tornado as far as determining the presence of a tornado and its location. That is sufficient for warning purposes.

I am NOT contending one can resolve the average or peak wind speeds. That is not necessary for warning purposes.

Mike

 

[Greg Stumpf]

I am NOT contending one can resolve the average or peak wind speeds. That is not necessary for warning purposes.

Hence the "not exactly". I think we both agree.

 

[MatthewCarman]

Matt Carman,
Just because there is a hole in the reflectivity at all doesn't mean the sky was clear in the "donut hole". Reflectivity is from precipitation, not clouds. Radar can barely pick up drizzle let alone condensation. If you had a satellite view of the event to confirm the donut hole was truly clear, that's a different story. Sounds like a very unique storm though.
Also, did you look at all of the different elevation scans? Or was this from a composite reflectivity?

Hi David, I was just looking at the radar that Dr Greg Forbes had up on TWC. This was before I bought GRLevel3 and was forced to rely on TWC, NWS etc for the radar. Dr. Greg Forbes said it was unique and pointed it out several times. The severe weather was ongoing in multiple states and he thought that was the most interesting storm. The donut hole lasted over 10 minutes. Thanks for the reply.