Observations from June 17, 2010

[Rob H]

Thanks for any help in advance!

Jeremy, I think I have some clear pictures of those same features, except with trees blocking the very bottom of the wall cloud. I'll try to find them when I get home. We were under the meso as it was forming and that cell really came out of nowhere.

Yes, we drove from near Alexandria, over to Buffalo, and down to Albert Lea on that chase

edit:

This picture is from 22:33z. I'm leaning towards a lot of that being scud - it had a very ragged base and cloud fragments were everywhere, as you can see from this pic. The velocity from that same time frame doesn't really seem to suggest the presence of multiple mesos (the rotation by Annandale and Howard Lake was from two discrete cells).

 

[Skip Talbot]

Jeremy, I watched your video and its quite interesting. For a good chunk of it the storm looked pretty outflow dominant as if it had long since occluded and gusted out. However, there appeared to be quite a bit of vorticity on the leading edge of the gust front that was resulting in weak funnels. I would generally refers to these as scud fingers though. They usually result from the rear flanking downdraft pushing out ahead underneath the base of the storm, condensing the inflow as its pushed up over the top of this mini frontal boundary. Even though the storm looked like it had gusted out, a new wall cloud definitely forms at the end of your video and drops a legitimate (although relatively weak) tornado. I've taken some screen shots and attempted to label them from what I can make out in the video, although its much harder to comprehend not having been there:

You have one mesocyclone at work here. The rear flanking downdraft is punching through the center of the updraft, creating a clear slot in the middle and making it appear like its divided into two parts. I draw in orange where the updraft base is, as its not bowed out into more of a horseshoe shape. I think you had a lot of scud action here, but don't doubt there was rotation in some of the features. It becomes a grey area when trying to draw the line between what's scud and what's funnels and how much rotation it requires.

This portion of the video more clearly shows this structure, with a strong RFD pushing out a gust front.

If I'm correct in the evolution of the storm, that updraft base continues to fan out while the storm cycles and a new wall cloud develops. This ultimately drops your tornado later on. Although there are gaps in the video here so I'm guessing.

 

[Jeremy Den Hartog]

Awesome - thanks guys very useful info!

 

[Chris Gullikson]

The double meso structure was quite impressive and I too was amazed that the old/western meso did not fully occlude and dissipate. It was also amazing how quickly the new meso formed and became tornadic.
Quite a day and I have really enjoyed seeing the many different perspectives.

Video from south of Kiester and then southeast of Kiester.
http://www.youtube.com/watch?v=AfMAIzakZtE

 

[Jeff Duda]

The double meso structure was quite impressive and I too was amazed that the old/western meso did not fully occlude and dissipate. It was also amazing how quickly the new meso formed and became tornadic.
Quite a day and I have really enjoyed seeing the many different perspectives.

Video from south of Kiester and then southeast of Kiester.
http://www.youtube.com/watch?v=AfMAIzakZtE

This is the kind of video I dream to capture. Great shots from a great position on a wild event, Chris! I like how you could see the levels of circulation, and the rotation on the wall cloud/collar cloud was intense even on video. Since video underplays reality, I can only imagine how rapidly that mass was rotating in real life (even though I was there I was a few miles to the west and didn't have such a great view of it).