Chasing South moving storms.

[Marko Korosec]

I didn't get to chase yesterdays super cells, because i was at work, but the storms went right through champaign so I got to see them anyway. I was curious on a south moving supercell like yesterdays storm, where the center of rotation usually is. We all know on a normal super cell moving east or north east to go to the south west corner.

In the early life of the storm the supercell definitely looked like it had a hook echo on the southwest corner. However, as the storms progressed, they still looked like two supercells (around 2:30-3:00 CST), but there wasn't any substantial hook echo, tornadoes were still being reported. As the storms were moving SSE if the south west corner of the storm was the center of rotation then the tornadoes would actually be in the front of the storm.

Now about 3:15 I was in Champaign county at work, and as the first supercell passed just east of us, we noticed three substantial rotations in the clouds, one of which produced a very short lived funnel cloud. eventially though the storm picked up speed and the circulation disapated.

Had I had the opportunity to chase this storm, im not sure whether it would have been better to get in behind the storm or in front of it. Granted most of the storms had rain wrapped tornadoes in them and chasing would have been difficult. But I would be curious what some of you would have done or did, for future reference.

Rob

 

[Jeff Snyder]

Don't try to think about it in terms of having to know where the meso for each storm movement direction. Rather, realize that the meso is USUALLY located in the upwind (up-shear?) side of the storm -- usually in a "back-right" configuration. Yes, in supercells moving east-northeast, the meso is typically in the southwest quadrant of the storm (southwest of the main precip core). But when a storm is moving east-northeast, there is typically southwest flow aloft (which is casuing the storm to move said direction), and thus the meso is located upwind, in this case, to the southwest. Perhaps it's better to say the precip is located downwind of the meso... Whatever, same idea...

So, in cases of northwest flow aloft, assuming southeast or south motion (for propagation/movement right of the mean wind, which is common for supercells), upwind would be northwest, and thus the meso is typically on the northwest side of the storm (or the precip is southeast of the meso).

Again, I used lots of "typically" and "usually", but that's just because, as we all know, storm configuration is all but concrete. There are cases, such as the 4/30 chase of the supercell near Weatherford, TX, where the meso was located pretty much south and southeast of the main precip, while motion was still to the east. By the way, this was the biggest HP beast I've seen, with awesome, yet confusing-at-the-time, structure. Radar showed this thing looking like a "C" at the time.. .nuts...

 

[Court Hubbard]

well that explains why i wasn't able to see a whole lot, i was on the wrong side, i mostly saw heavy rain. that clears everything up. great information to know, i will keep that in the memory bank.

 

[mikedeason]

Court, don't feel too bad. It's takes a while to learn even the basics and there are some chasers who don't chase northwest flow severe weather events at all (typically because they tend not to produce many tornadoes but lots of strong wind and hail.) Under some conditions, I prefer these types of storms to early season 50mph express lane supercells.

When chasing in general, I generally take the approach of not orientating myself to compass points but to the storms and their movements based on conceptual models. Sometimes it bites you in the butt.

July 12th is a good example where the conceptual model lead me to make a so-so decision by staying on the wetern flank of the storm. Experience has conditioned me to expect new updrafts to develop on the upwind side of an existing storm or storm cluster; usually you have to be on them right as they are developing if you are going to have a good chance of seeing a tornado. So I tried to stay west-to southwest of the precip core and rainfree base/updraft region.

Meanwhile, just a hop, skip an a jump to my east and in an area where I generally wouldn't be, Mike H was wintnessing some very photogenic storm structure.

So the conceptual mode approach is a good method to start with, but remember, results may vary.

Regards,

Mike

 

[Shane Adams]

I adjust my angle of (preferred) approach by SRM, following the same general "rules of engagement" of my own. For a south-moving storm, I'd prefer to be west of it, as this puts me well within the view of the main updraft, and away from nasty things like rain and hail that can ruin a good tornado op.

I'm so glad I passed through my "I wanna get my windshield shattered" phase without ever accomplishing that feat. I can count on one hand (minus thumb) the times I've been in hail (of any size) the past year or so.

 

[Bob Schafer]

There are cases, such as the 4/30 chase of the supercell near Weatherford, TX, where the meso was located pretty much south and southeast of the main precip, while motion was still to the east. By the way, this was the biggest HP beast I've seen.

The meso of an HP storm can often be found to the SE or E of the precip (If it can be found at all, LOL!)

HP storms, vs others, are usually the result of plentiful precipitable water, or deep layer moisture, from which the storm is feeding, in conjunction with light to moderate mid and upper level winds failing to ventilate the storm enough to keep it from being HP.

I think.

More knowledgeable types, correct me.

Seems that I've seen quite a few HP in CO.....but you wouldn't expect the rich deep layer moisture to be in CO as often as I've seen HP there. My guess is that the elevation in E CO allows the mesos to essentially be closer to the ground, the storms wrap the precip back around the W side of the mesos with less protest from the wimpy (because they are much less dense) sfc winds, and the other orographics in the area really mess with the mid level winds and the storms get confused, LOL.

Thought I'd give the mets a good laugh at THAT theory! :lol:

Bob

 

[Robert Dewey]

HP storms, vs others, are usually the result of plentiful precipitable water, or deep layer moisture, from which the storm is feeding, in conjunction with light to moderate mid and upper level winds failing to ventilate the storm enough to keep it from being HP.

Yep, you are right.

Yesterdays storm in IL actually had decent mid level winds (50knts at 500mb), so that would probably put it into the "hybrid" catagory...

 

[Thomas Loades]

The meso of an HP storm can often be found to the SE or E of the precip (If it can be found at all, LOL!)
Bob

Is there precip ahead of the meso in an HP supercell — like from under the anvil? Just in looking at the picture of the HP in the NOAA Advanced Spotter Guide, it doesn’t quite look like it . . . just more distant precip . . . unless it only looks that way because there’d be less cloud to make the rainshafts darker under the anvil than the updraft base.

 

[Bob Schafer]

Is there precip ahead of the meso in an HP supercell — like from under the anvil?

There's quite a lot of precip everywhere with an HP, thus the name.

Don't get too hung up on depictions in spotter guides. While they are an excellent source of wisdom, and storms do have identifiable structures that every chaser needs to know, it's equally important to understand that every storm is unique. The spotter guides illustrate the "normal" storm structures, but some weird storm characteristics are seen now and then. HP's are especially prone to deviating from the "normal" structures, and that's just one of the reasons we hate to chase the damn things.

The greater reason is the danger because of the lack of visibility, and ya gotta keep a safe distance!

Bob