4/11/07 DISC: IL, IN

[Bob Hartig]

I don't normally initiate discussion threads; I think my subject here is appropriate for starters, but if it's better placed elsewhere, then Mod, please move it.

I nowcasted for my chase partner yesterday on the Indiana storms, so I was on GRL3 for most of the afternoon and evening, and I was struck by one thing: the lack of velocity couplets and TVSs. The Arcadia supercell held together for a long time and had a beautiful reflectivity return. It was scooting along up by the warm front in an area of nicely backed winds and mid-50s Tds, and I could not for the life of me figure out why nothing was showing on SRV except, maybe once or twice, the very vaguest indications of rotation. I mean, just nothing to make me look and think, Bingo!

Did I miss something? Did anyone else have a similar experience?

[Skip Talbot]

I was watching it on and off yesterday. These were low topped storms, definitely not monster supercells scraping the stratosphere. Is it possible that the scale of the rotation simply escaped the resolution of the radar?

[Bob Hartig]

I wondered that myself, but you'd think something would at least show up at base level.

[Skip Talbot]

These storms may not have been capable of developing large mesocyclones, but at the same time would have been more than capable of producing tornadoes as they interacted with boundaries and traveled through areas of good low level shear.

I believe that when we look for couplets on the radar, even at SRV1, we are usually just identifying the meso, and not the tornado itself. The SRV1 beam from KIND is already over 2000 feet when it passes over Arcadia, well above the storm's base.

[Jared Farrer]

These storms may not have been capable of developing large mesocyclones, but at the same time would have been more than capable of producing tornadoes as they interacted with boundaries and traveled through areas of good low level shear.

I believe that when we look for couplets on the radar, even at SRV1, we are usually just identifying the meso, and not the tornado itself. The SRV1 beam from KIND is already over 2000 feet when it passes over Arcadia, well above the storm's base.

Yes these were low topped storms, the meso's were not very deep (i.e. 10,000 feet or more) but rather shallow. Sometimes mini-sups are so shallow they barely show up on radar at all. But the descret cell that moved through hendricks county was a decent sized storm with tops around 34,000 feet and was decently wide. One thing though was that the storm went from intense to dieing back to intense in a rather short time. I actually left the storm when it weakend quite a bit in boone county, a big mistake on my part. But being as far from the KIND radar as it was, a hook did not really appear until around the time of the hamilton county tornado. And it was only visable for a few minutes. Then the line behind the sup kinda just ate the cell.
Sorry trying to keep this in the parameters of a reports thread, I guess I will throw in another picture to do so.
http://i101.photobucket.com/albums/m62/superjdf/IMG_0928.jpg

[AlDanks]

Had meetings and couldn't chase. Did find a link to some video for the Hamilton County, IN tornado.

http://www.wthr.com/

[John Farley]

On the point of radar mesocyclone detection, two things. First, there were some warnings based on radar, so there must have been something there. However, it is true that mesocyclones are often harder to detect in mini-supercells than in regular ones. The following link may be helpful in that regard:

http://www.crh.noaa.gov/lmk/soo/docu/mini_supercell.php

See especially the sections on mesocyclone structure and radar sampling issues.