QLCS/Mesovortex Storm Structure

[Joey Prom]

So, I was chasing a QLCS/Mesovortex type of tornado setup yesterday and I realized, I really don't know what to look for. I know to look for kinks in the line on radar, and I was positioned perfectly, but visually I don't know what to look for as far as storm structure. Will there be a wall cloud? If so is it on the shelf? Behind the shelf? Or is it similar to a horseshoe on a Supercell, where the wall/tor will be where the horseshoe curls back in on itself to the north? I am assuming that most QLCS spinups/mesovortexes will be imbedded pretty heavily, so to get visual do you have to be very deep in the kink/notch to see them? ie almost directly under the shelf? (in which case nopers unless I have a really good East or NE PAVED road. (Learned that lesson for the first time yesterday.)) Because these storm modes are more common than classic discrete or even HP supercells, I really need to know what to look for, as I will likely be chasing this type of storm mode the most often, especially during the summer months. Thanks all.

 

[rdale]

QLCS Tornadoes/ Angular Momentum

Hey i've been looking around and can't seem to find an awnser to this. First How exactly do mesovorticies in squall lines form? And if those are such small circulations should'nt they be stronger than the usual EF-0/EF-1 because of the conservation of angular momentum?

stormtrack.org

 

[Joey Prom]

Thanks. But that thread is mostly about the theory/spotting on radar. I know what to look for on radar, and the theory is good information to have stored away for forecasting/nowcasting, but I am asking more about practical storm spotting/storm structure identification.

 

[Jeff Duda]

Chasing a squall line for rotation/tornadoes is a complete crap shoot. Circulations can pop up anywhere along the line at any time if the low-level shear is sufficient in magnitude and velocity. The radar presentation isn't going to give you any advanced warning that a tornadic circulation is developing - it will only tell you when one has formed. Chasing meso-beta-scale aspects of the line such as a bookend vortex will rarely pay off, and you'll probably end up missing more tornadoes along the front of the line than you would ever see by chasing that bookend vortex.

 

[John Farley]

I have seen QLCS tornadoes twice in 25 years of chasing, and I used to chase a lot in the Midwest, especially Illinois, where they are a common type of tornado. Interestingly, both times the squall line had just passed me, so I was looking to the east or southeast, and was lucky enough that there was not much rain between me and the spinup tornado. Both were brief and caught me by surprise. One of them consisted of an area of rotation in the cloud base and a large dust swirl underneath, with no funnel cloud. The other one consisted of an area of rapid motion and rotation in scud under the cloud base, and came and went so fast I could not even get a picture or video. Didn't help that I was trying to get through a town at the time it happened. I would agree with what Jeff said above - a complete crap shoot. Having said that, the first chase tornado I ever caught was in a squall line, but in an embedded HP supercell, that persisted for quite a while (i.e. through several tornado warnings) so I could position ahead of it and then got lucky that tornado dropped just when I was in position (and maybe even luckier that I did not get caught in the tornado, which I almost did, thanks to my lack of experience and rookie mistakes like losing track of what direction I was going.)

 

[Joey Prom]

Thanks John. Yea I would never drive more than 3 hours for a QLCS tornado chase, but more often than not on the "local" chases/when I am out spotting that is what I get.

 

[Jeremy Perez]

I managed to time lapse a line that featured what appeared to be a mesovortex three months ago in northwest Arizona. Pretty interesting to watch an outflow surge on the south/left side of the line try to wrap a notch into it. The process had a messy, RFD-esque quality to it and led to a lowering at the confluence. Not sure if that helps. It's not something I'm very familiar with.