What is a flying eagle, or something like that.

[Greg Stumpf]

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.

 

[Glen Romine]

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

 

[Robert Dewey]

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

 

[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

 

[Robert Dewey]

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?

 

[Glen Romine]

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