What is a flying eagle, or something like that.

Bryan Bjorkman

I've read posts where people are talking about the double eagle on radar. What is that and what is the significance?
 
David
Since your online I am curious, in the video that you put together (excellent btw) after dark there was a funnel illuminated by lightning that you called in. Where exactly was that? I live in Lincoln and was south of the Hallam storm. I ended up running more than chasing after dark that night, lol. I flew over the entire track the next day and saw numerous other wind/tornado damage, just trying to get an idea of that funnels location. Thanks
 
Originally posted by Bryan Bjorkman
David
Since your online I am curious, in the video that you put together (excellent btw) after dark there was a funnel illuminated by lightning that you called in. Where exactly was that? I live in Lincoln and was south of the Hallam storm. I ended up running more than chasing after dark that night, lol. I flew over the entire track the next day and saw numerous other wind/tornado damage, just trying to get an idea of that funnels location. Thanks

Going to PM you so as not to swing way off topic on this thread. :wink:
 
Originally posted by Mike Hollingshead
[Broken External Image]:http://www.extremeinstability.com/stormpics/ainsworth7-24-00anim.gif

Man I love July in NE. Seems like about once a year(or more) there is a long-lived 'flying eagle' dropping south in the central part of NE.

Mike, would you say that's an HP sup judging off the broad range of high reflectivity? It certainly looks like it might be a little bit more work to chase because the core is bearing down on you if you setup on the southern flank. I guess you have to work this one from behind the hook.
 
Just adjust your position based on storm movement. SSW would be decent here. Remember, storms don't know directions. Think like the storm, become one with it! :wink:
 
Actually I've had the best luck EAST of the updraft base on those, or slightly south of due east. It was a classic.

http://www.extremeinstability.com/july_24,...a_tornadoes.htm

Both that one and the July 12, 2004 Bartlett storm were dropping ssw and I was pretty much straight east of the updraft base on both. If you are close enough to the updarft base and nearly under it precip blocking the view often isn't THAT big of an issue. The updraft is moving/forming south and the precip is being left a little "behind" it to the ne as it is vented to the east. So best viewing is still to the east. Others may say differently but from what I've seen.....

Edit:

http://www.extremeinstability.com/04-7-12.htm

East of updraft....
 
Looking at your pics Mike, is it fair to say that the majority of the precip was fairly well separated from the updraft base, giving you a little more manuevering room in there?
 
If it is a flying eagle it is fair to say it is fairly well vented yeah. There will still be precip....likely hail...close to that updraft base. But, like I said, often if you are east of that updraft base most of the precip is lagging a bit "behind" as it moves south-ssw. So most cases you are still going to be ok to the east to slightly south of just east. On the July 12 04 one there wasn't a great deal of venting(other than its storm motion helping out). It had about 20 knots at 500mb out of the west and 40 knots at 300mb out of the wnw and was very striking visually. Only 3-4 miles up the road to the north of me and you were in a whole nother world of heavy rain...but that was getting more ne of the updraft base.
 
I'm surprised that nobody has replied to offer the explanation for the shape of the echo, particularly the V-notch in the forward flank. Some feel that this is the result of "flow around the obstacle", with the obstacle being the updraft, with the notch being the wake. Comments?
 
Originally posted by Greg Stumpf
Some feel that this is the result of \"flow around the obstacle\", with the obstacle being the updraft, with the notch being the wake. Comments?

Are you one of the 'some'? Just curious. I agree that this is a tempting explanation - as the updraft carries the momentum of surface air aloft - and theoretical and model calculations have indeed shown the stagnation high that develops aloft on the upshear side of the updraft. But, a strong updraft is a signature feature of supercells, and not all supercells show the flying eagle / v-notch signature, though some cells seem to show it at various times and not others. You could perhaps argue that the updraft often sits along the right flank edge, but moves closer to centerline as the mesocyclone intensifies and then is more apt to block the flow through the main precip core, but I've never seen this transition clearly demonstrated in a study. There might also be reason to suspect differences in microphysical processes as being a player, as polarimetric radar data suggests. I've never seen a satisfying explanation of the cause beyond the blockage one - but I'd be interested if anyone knows of a definitive description of this phenomena.

Glen
 
Originally posted by Glen Romine+--><div class='quotetop'>QUOTE(Glen Romine)</div>
<!--QuoteBegin-Greg Stumpf
Some feel that this is the result of \"flow around the obstacle\", with the obstacle being the updraft, with the notch being the wake. Comments?

Are you one of the 'some'? Just curious. I agree that this is a tempting explanation - as the updraft carries the momentum of surface air aloft - and theoretical and model calculations have indeed shown the stagnation high that develops aloft on the upshear side of the updraft. But, a strong updraft is a signature feature of supercells, and not all supercells show the flying eagle / v-notch signature, though some cells seem to show it at various times and not others. You could perhaps argue that the updraft often sits along the right flank edge, but moves closer to centerline as the mesocyclone intensifies and then is more apt to block the flow through the main precip core, but I've never seen this transition clearly demonstrated in a study. There might also be reason to suspect differences in microphysical processes as being a player, as polarimetric radar data suggests. I've never seen a satisfying explanation of the cause beyond the blockage one - but I'd be interested if anyone knows of a definitive description of this phenomena.

Glen[/b]

I personally like the updraft theory. It would make sense that mesoscale divergence aloft would be generated because upper level winds are being forced around an object. While upper level divergence usually leads to ascent, I believe in this case that the "forced" divergence may actually lead to descent. This is because the airstream would try to rush back in behind the storm, and actually converge, causing descent, much like the rear inflow jet, and the associated Weak Echo Channel. I have illustrated this quickly to show what I mean:

http://69.14.190.10/images/storm_theory/st..._divergence.jpg

And then applied to an actual storm:
http://69.14.190.10/images/storm_theory/52896_pic5.gif

The way I like to look at it is like a rock in a stream of water. The water moves around the rock, diverging... But, on the other site of the rock, the water actually flow TOWARDS the rock, and with a downward motion...

I hope I am making sense :lol:
 
Originally posted by rdewey
The way I like to look at it is like a rock in a stream of water. The water moves around the rock, diverging.

One of the concerns about the obstacle theory is that the updraft is not a solid body, like a rock in the stream. The updraft is also fluid.
 
Also, you need to be careful about the layout of the blockage (updraft) relative to the storm features. In your diagrams, the split is not where the updraft is located. Here is perhaps a better representation:

[Broken External Image]:http://www.atmos.uiuc.edu/~romine/img/notch_model.jpg

The peach color is the main precip core (say > 40dbz), the purple is the storm updraft, green arrow aligned through the main updraft aligned with the mid-level flow, blue lines maring the wake region downshear from the updraft, the 'H' and 'L' the relative mid-level pressure fields owing to the blockage by the updraft, and the black lines might represent the perturbation flow around the blockage. The yellow flow pattern sort of seems to make sense to me, as in the acceleration of flow around the north side of the updraft elongating the reflectivity field as shown. However, the lobe on the south side of the echo doesn't seem as intuitive in this perturbed flow model - as you'd expect the southern edge to be heavily rounded as the echo 'emerges' out from behind the flow obstruction - but instead it seems to not really fit.

As most folks that have hung out in cores much can tell you, the hail is located immediately north to northeast of the updraft for a layout as shown in the image above, and smaller hail often extends down the 'wing' (southern half of 'V') of the eagle shaped echo, with typically just heavy rain in the 'body' (northern half of 'V') portion of the echo. The reason for the void in between might be in part due to the perturbed flow due to the updraft, but the southward extension of the echo probably has more to do with extreme storm-top divergence fanning out the precipitation at the top of the updraft.

Glen
 
Originally posted by Glen Romine
As most folks that have hung out in cores much can tell you, the hail is located immediately north to northeast of the updraft for a layout as shown in the image above, and smaller hail often extends down the 'wing' (southern half of 'V') of the eagle shaped echo, with typically just heavy rain in the 'body' (northern half of 'V') portion of the echo. The reason for the void in between might be in part due to the perturbed flow due to the updraft, but the southward extension of the echo probably has more to do with extreme storm-top divergence fanning out the precipitation at the top of the updraft.

Glen,

You may have hit the nail on the head here. The shape of the reflectivity echo in the forward flank may be due to the distribution of hail versus rain in the core. Perhaps the reflectivity in the right "wing" of the core has more of a hail contribution, and thus appears more intense on radar.

Just a thought. It would be nice to compare storms with and without the downwind V-notch to a dense network of surface precip obs. Of course, those kinds of data sets are nearly impossible outside the realm of special field projects.
 
True Greg, but if you can sell yourself on the polarimetric radar fuzzy logic algorithms that identify hydrometeor types being reasonably accurate, then there are observations there that support this idea. While not the best demonstration, the polarimetric obs from the May 8 2003 OKC tornadic cell (image from CIMMS) with a moderate V notch signature shows hail only along the southern half of the V along with big raindrops which have enhanced reflectivity signatures, with mostly just heavy rain in the northern half.

[Broken External Image]:http://cimms.ou.edu/~heinsel/jpole/cases/20030508/supercell_HCA_2003-05-08_at_22-29-31-UTC.png
 
Originally posted by Greg Stumpf+--><div class='quotetop'>QUOTE(Greg Stumpf)</div>
<!--QuoteBegin-rdewey
The way I like to look at it is like a rock in a stream of water. The water moves around the rock, diverging.

One of the concerns about the obstacle theory is that the updraft is not a solid body, like a rock in the stream. The updraft is also fluid.[/b]

Yes, but I am thinking that a very strong updraft would change the mid and upper level flow on the mesoscale aspect, moreso vertically than horizontally. The updraft may force upper level winds vertically up and over the updraft, which would descend back down on the other side. Looking at Glen's v-notch model, the "green line" (wind flow) would be pushed up and over the updraft, then descent on the other side.

I believe that a "v-notch" is the same as any other supercell. Take a NEXRAD image of a "v-notch" supercell, and fill in the "v". It looks like any other supercell - Where the north side tends to be weaker than the south side (or vice-versa - take an ordinary supercell and remove a section in the shape of a "v"). This could be because the south side is closer to the moist inflow, more unstable air, strong mesoscale convergence between the inflow/outflow, etc..

Why would some supercells exhibit this, while other's do not? One reason could possibly be that if the upper level winds are too strong, then they would just tend to plow through the upper portion of the updraft , without much in the way of any vertical movement (and visually, you might just have a "dome" on top of the supercell, as opposed to an all out solid overshooting top). When I say upper level flow being weak, I am meaning in contrast to the actual updraft. If you have a screaming 120KNT upper level jet in a relatively low CAPE situtation, the upper level winds should have no problem plowing through the updraft.

I was searching for some radar and satellite images, of v-notches, and found this from the Stormgasm site: http://stormgasm.com/5-5-02TXPanhandleTorn...rnado/radar.htm

There appear to be some very good examples of v-notches, and if you looks at the Infrared satellite imagery, you can actuall see the storm top/updraft area in bright red, while directly behind that area, you can see lower cloud tops, indicated by blue. This may or may not be a problem with the satellite, but I see that both v-notch storms have this "descending" pixel:
http://stormgasm.com/5-5-02TXPanhandleTorn...F.satbetter.gif
 
Winds don't flow up over the updraft, they flow around it. Look at a sounding and this should make sense. The sat image of the warm hole with cooler temperatures in a half ring upstream also comes from the backbuilding anvil knuckling up at the base of the tropopause - where temperatures are colder, and the overshooting top extends up into the stratosphere - where temperatures are warmer than they are down at the tropopause - so the warm spot you noted is actually higher up in the atmosphere than the surrounding cooler air.

Glen
 
Originally posted by Glen Romine
Winds don't flow up over the updraft, they flow around it. Look at a sounding and this should make sense. The sat image of the warm hole with cooler temperatures in a half ring upstream also comes from the backbuilding anvil knuckling up at the base of the tropopause - where temperatures are colder, and the overshooting top extends up into the stratosphere - where temperatures are warmer than they are down at the tropopause - so the warm spot you noted is actually higher up in the atmosphere than the surrounding cooler air.

Glen

Gotcha... From what I gather, the reason the upper level wind couldn't go up and over the updraft is due to an inversion because of the said temperature increase?
 
Originally posted by rdewey

Gotcha... From what I gather, the reason the upper level wind couldn't go up and over the updraft is due to an inversion because of the said temperature increase?

Again, just find yourself a sounding - and start looking at parcels lifted from mid-levels. You do this the same as you would for lifting a surface parcel on a sounding - there are tons of examples of how to do this on the web if you are unclear about the concept. So, what you can quickly convince yourself is that lifting air parcels at mid-levels and above are almost never even neutrally buoyant (as in lifted air parcels are colder than their environment) - too little moisture up there - and you'd need nearly dry adiabatic lapse rates to even get that. Instead, these lifted parcels are negatively buoyant and would quickly sink back to their original height. This is particularly true for air lifted through the tropopause - a strong inversion at the top of the troposphere - where this effect is highly amplified.

Glen
 
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