DISC: 4/23/06 KS/CO

[Ryan McGinnis]

Just curious -- has anyone else out there ever visually seen an obvious supercell and yet found that it had zero radar returns? This happened with me on Sunday. The cell that Darren and me were on visually looked quite impressive, yet was producing no radar signature for a good 15 minutes. When it did start showing a signature, it was very, very weak -- it looked like tiny shower or something. It took a good half hour before it looked like a supercell on radar.

Is this because the storm was highbased and the tilt-1 that we were looking at was scanning too low? If not, then what sorts of things can cause such a lack of radar returns? Is there a composite reflectivity archive somehere on the net? I have the BREF tilt-1 images which indicate that the storm wasn't visible at all on radar until around 23:55Z, and it looked impressive well before that; I'd be interesting if the higher tilts 'saw' the storm earlier, or if the storm was just LP in nature.

Here's a link to the BREF radar archive starting at 23:55. The cell in question shows up on radar just north of the interstate. Again, we were watching this thing form and it had a very impressive anvil and vault a good thirty minutes before 23:55Z.

Radar link

You can already see it on the 23:30Z sat shot:

Sat shot

 

[Dustin Wilcox]

Its kind of funny you bring this up, because yeserday afternoon while chasing a storm just SE of the Dodge City XM was showing a pretty strong storm that appeared to be full of heavy rain and hail but upon intercepting the storm it was very very high based and had a downdraft that one could see right through I guess thats what one get for chasing in 90 degree temperatures with 50 degree dewpoints.

 

[Kurt Silvey]

Ryan,

I stopped in Concordia about 23:50 for one last radar check before I completely pulled the plug and headed for home. I saw that cell developing and watched it until about 00:10. I was switching back and fourth between tilt 1, 2, & 3 to try and get the best view. Tilt 2 seemed to be the best. I finally said screw it and left because I had just been in Ellsworth about 45 minutes before, and I didn’t want to drive back down there. I think it may have something to do with the amount of precipitation in the cell, if its all ice and not raining there won’t be a good wave return. I’m sure there is someone who could provide a better explanation though.

 

[Tom Stefanac]

Ryan,

I stopped in Concordia about 23:50 for one last radar check before I completely pulled the plug and headed for home. I saw that cell developing and watched it until about 00:10. I was switching back and fourth between tilt 1, 2, & 3 to try and get the best view. Tilt 2 seemed to be the best. I finally said screw it and left because I had just been in Ellsworth about 45 minutes before, and I didn’t want to drive back down there. I think it may have something to do with the amount of precipitation in the cell, if its all ice and not raining there won’t be a good wave return. I’m sure there is someone who could provide a better explanation though.
[/b]

Looking at some level 2 data here from the university, the storm was there, it is almost impossible for a supercell which has some form of downdraft not to register. A downdraft implies there is some form of precip in the cloud and you visually observed slight precip so whatever was there was registering but below 5dbz. Actually between -5dbz and 5 dbz you can quite clearly see the storm as a large glob. I will try and post some screen grabs or you could just wait for the NCDC archives to post it.

 

[Darren Addy]

Not to change the subject on this storm, but...

Reviewing my video tonight I discovered something fascinating about the funnel clouds we saw. The first funnel cloud is rotating cyclonically. Then, higher up, a thinner funnel appears that is rotating anticyclonically. The pair lasted a good 1-1/2 to 2 minutes. The anticyclonic funnel disappeared into the slot and since the feature was rapidly coming over us, we picked that time to move down the road.

McGinnis is looking at it now and says it appears that the RFD actually split the wall cloud, the force of which apparently rolls funnels one way and the other side rolls the other.

The difference in their rotation is noticable when you speed up the playback. I know that Amos and company also got video of these funnels, so maybe they could share their observations. I don't think I'm imagining things. I'll edit this post with a link to the video clip when it is uploaded.

Darren Addy
Kearney, NE

 

[Darren Addy]

Ryan McGinnis has (I believe) flipped the sequence of two of his storm pics (as you can tell from the position of the setting sun) but those two pictures actually give you a nice before/after of the wall cloud before it was ripped in half by the RFD. (At least I think it was a wall cloud and I think it was an RFD - alternative explanations are certainly welcome) :unsure:

In fact, I think in the "before" picture you can see the RFD already ripping into the wall cloud from behind. The after picture is when it has split the wall cloud, rolling up the two funnels (one cyclonic and the other anticyclonic) and pushing them apart. I've taken Ryan's pics and put them in the proper sequence (cropping out all but the wall cloud), giving you one "plain" and the other with what I think I'm seeing:

You will see the actual rotation of each of these funnels on the video (speeded up motion).

Comments/corrections?

Darren Addy
Kearney, NE

 

[Darren Addy]

Edited: to eliminate my confusion. I believe my first set of images is labeled correctly.
The rotation would be from the perspective of above (satellite) not below. My newbie-ness is showing.

Meso/wall cloud is rotating counterclockwise, as is the larger funnel.

Darren Addy
Kearney, NE

 

[Darren Addy]

6.2 MB QuickTIme clip of cyclonic/anticyclonic funnel formation here:
http://www.lopers.net/weblog/podtest2/
Storm motion is sped up so you can more easily discern rotation.

Darren Addy
Kearney, NE

 

[Ryan McGinnis]

6.2 MB QuickTIme clip of cyclonic/anticyclonic funnel formation here:
http://www.lopers.net/weblog/podtest2/
Storm motion is sped up so you can more easily discern rotation.

Darren Addy
Kearney, NE
[/b]

Actually, if you look really closely at the anticyclonic funnel, you'll notice that you can see that it looks "braided" -- i.e., several small funnels spinning around each other.