Hook Echo question

[Rodney Cuevas]

Wow this is my 1st post... I should definitely know the terminology of this but I fail.. The severe outbreak tonight (Saturday June 5) that is occurring/occurred in IL, noticed that a hook was wound so tight that the rain shield wrapped all the way around the verified tornado on radar. Is there a term used for that? when the precip is wrapped around and shows that "doughnut" image??

 

[Wes Carter]

It's when the meso occludes and becomes rain wrapped that it happens. Whatever meso was there dies out when the inflow is cut off by the rain wrapping around the meso. Sometimes the cell is just cycling and a new meso will form below or behind the one that occluded.

 

[Rodney Cuevas]

Occluded Meso..... Much thanks! I couldn't rem the term when it made that doughnut shape on radar..

 

[Rich Long]

Welcome to stormtrack by the way!

 

[Jeff Richardson]

Wow this is my 1st post... I should definitely know the terminology of this but I fail.. The severe outbreak tonight (Saturday June 5) that is occurring/occurred in IL, noticed that a hook was wound so tight that the rain shield wrapped all the way around the verified tornado on radar. Is there a term used for that? when the precip is wrapped around and shows that "doughnut" image??

Welcome to Stormtrack! I think you'll really like it here and learn a great deal.

Wes is right about the meso becoming rain wrapped with inflow cut off. This can also happen in supercells when the Rear Flank Downdraft (RFD) does the same thing but without the precipitation. I've seen this happen numerous times in the southern and high plains and...if I remember the correct terminology...it's called 'cyclic tornadogenesis.' When the conditions are just right, some supercells can 'cycle' repeatedly and produce as many as 20 separate tornadoes.

 

[John Wetter]

I think the radar term you're looking for is a Bounded Weak Echo Region, or a BWER.

 

[Andrew Ryan]

I think the radar term you're looking for is a Bounded Weak Echo Region, or a BWER.

BWERs and occluding mesos are two different processes. A BWER shows up when a strong updraft holds precip aloft in the storm. This is results in the donut hole on radar.

An occluding meso occurs when the RFD cuts off the updraft of the storm. In a cyclical supercell, the new meso will develop northeast of the old meso.

 

[Patrick Marsh]

A BWER shows up when a strong updraft holds precip aloft in the storm. This is results in the donut hole on radar.

You can have a donut hole type shape from other processes. It depends on what level you are interrogating. If the signature is aloft, the donut hole is most likely the result of a BWER. If the donut hole is on the lowest tilts, it could very easily be from a tornado wrapping up. Come find me this week in the NWC and I'll show you several CASA examples of the "donut holes" actually resulting from tornadoes, not BWERs.

An occluding meso occurs when the RFD cuts off the updraft of the storm. In a cyclical supercell, the new meso will develop northeast of the old meso.

Again, not always the case. In fact, most new mesocyclones that I've seen tend to develop to the southeast side of the old mesocyclone. It's this redevelopment of a supercell updraft on the southeast side of the old updraft that gives the "turning right" appearance.

 

[Andrew Ryan]

Oops. Thanks for the corrections. I knew that the new meso developed somewhere on the east side, but for some reason NE stuck out, probably mixed that up with the storm motion.

 

[Danny Neal]

 

[Adam Lucio]

Interesting topic, I thought it was a BWER regardless of where it is or what is causing it.

Hard to say whether the image above was an occluding meso or an actual tornado. You can see where our position was and we did not have a great view at that time. Tornado reports were coming in at that time however.

 

[Jason Berner]

I would say that from following these storms, that is more of the occluded meso as mentinoed. The RFD did end up wrapping all the way around the storm and there are numerous reports of tornados at and around this time/area so I would expect that it would be more of the tornado wrapping up as Patrick mentioned here.

Plus this image is another good example that the new updraft will likely occur to the SE of the storm. If it formed into the NE, it would form in the heavy precip. and, in a lot of scells, the hail core. The downdraft with this heavy precip. core would work to really diminish a new updraft forming in this region whereas a new one to the SE is in "clear" air, so to speak, and would not be effected by precipitation.

 

[Rodney Cuevas]

Much thanks for the welcomes. Definitely look to learn a lot from all of you and help others learn/add any expertise that I may contribute.. Being from the Gulf coast I am much more familiar in the tropical subject than severe but I am trying to learn as much post secondary college education on severe side as possible. In this field always have to maintain a certain humility b/c the one time you think you may know it all, the science turns around a bites you.

Again, much thanks for the solid responses.

 

[Greg Blumberg]

I wish the smoothing wasn't on that picture otherwise I could approximate how far away the storm was from the radar by using the bin size. The "doughnut hole" you could be seeing in that picture could be an artifact from the smoothing algorithm. I don't trust the smoothing algorithm produced by the GR products for that reason.

Either way, it looks like the radar is hitting the low levels of the storm due to the shape of the inflow notch region. I don't think you can pick up "eyes" like that from Level 3 data, and even from an 88D at that. You might be able to if the radar is close, but then again I can't tell.

 

[Rob H]

I don't think you can pick up "eyes" like that from Level 3 data, and even from an 88D at that. You might be able to if the radar is close, but then again I can't tell.

I'd be inclined to agree. 05/10/10 Wakita was a good example of a powerful storm and it passed over VNX, yet you can't make out the "eye" on level 3 data - only on the level 2 data. I could only find a picture of the level 3 hook, but I know at the time there was an "eye" on the level 2):