jpeters3

cell behind it tightening up

debris signature on mccomb storm

6 minutes ago, Indystorm said:

 

Thank you guys for explaining how the LL lapse rates contribute to breaking the cap when one is present.

It's really an issue of low-level buoyancy.  If you can get enough low-level buoyancy, that aids (or at least doesn't act as a deterrent) in the vertical stretching of near surface vorticity, then you are golden.  Likewise, weaker low-level laps rates equates to less low level acceleration and makes it harder to stretch near surface vorticity.

So there may not necessarily be a CAP (there could be no CIN), but it's still hard to punch through the layer with very weak buoyancy.

It is possible for low-level dynamics to overcome this issue, but we don't really have a good understanding at this point of which conditions do, and which do not permit this "compensation." 

For those of you who are more technically inclined, it's not actually the low level buoyancy that does the near surface stretching.  It's actually the buoyancy-driven low pressure that sits at the updraft bottom, and the associated upward accelerations below the updraft base and the center of this low pressure.  When low-level buoyancy is stronger, this low pressure feature is also stronger.  Note that this effect is separate from the low-level dynamic accelerations driven by rotationally driven low dynamic pressure.

5 minutes ago, Indystorm said:

I think Quincy somewhere back in this thread said something to the effect that you don't need low level lapse rates to be great if other parameters are off the charts.

He has been touting that for days, but obviously they are limiting things here.

Just now, METALSTORM said:

You can view it through this local station. 

https://www.myarklamiss.com/live-stream/

Thanks!

Unfortunately you can't view KULM on radarscope...

trying to fire ahead of main line

5 minutes ago, Bob's Burgers said:

Something to consider is the placement of the qlcs right now vs where there 15z hrrr pegged it in its 2 hour forecast -- real obs would suggest this line is moving much faster than the HRRR forecast, limiting warm sector opportunity for open sector supercells. jmo

This is a very good point.  The 15 UTC HRRR is a little too far north, a little slow, and seems to be a little too discrete with this QLCS convection.  Hard to tell what downstream impacts this might have, but it make me a bit skeptical of that solution.

worth noting that a robust ofb is evident along the SE flank of the line. This means that tail end spin ups along the line are unlikely. 

15 UTC HRRR is breaking out a line of supercells ahead of the QLCS in the volatile part of the warm sector....

Just now, Jim Marusak said:

moderate or high I don't think really maters at this point. it's probably more a worry now of PDS tornado Watches and normal Tornado Watches than anything else.

Obviously SPC outlooks have no impact on what will actually happen, but it's fun to speculate on what the SPC forecasters will do.

3 minutes ago, Cheeznado said:

I bet SPC is pondering an upgrade to high. 14Z HRRR shows an increase in the number of significant UH tracks.

Though, the HRRR solution is showing a lot of this activity (aside from the huge UH tracks with the QLCS) along the tail end of the line.  So far, this region as been fairly inactive. 

Edit: after another look, I'm having trouble interpreting what the model is showing.  At one glance, I can convince myself that it shows widespread supercell coverage.  At another glance, I can convince myself that it's just showing a QLCS mess.  Either way, it seems every probable that numerous QLCS tornadoes will happen today given this morning's trend, and that some of them might be strong.  That alone, along with the more uncertain warm sector, might be enough to warrant an upgrade to HIGH.

1 minute ago, Quincy said:

5.1 C/km 0-3km lapse rate... jives with mesoanalysis. A good example of why you don’t necessarily need steep low-level lapse rates when you have low LCLs and substantial low-level shear. 

 It's also worthy of note that the sounding is nearly moist neutral below 2.5 km, so it's likely that also helped things.  Parcels in moist neutral environments should have no resistance to ascent, and do not experience deleterious effects from entrainment.  Could be a totally different story for a sub-saturated environment with a similar low-level lapse rate.

new circulation 

1 minute ago, DanLarsen34 said:

That radar signature is suggestive of at least an EF-3. Yikes. 

Seems like this was a fairly "hefty" QLCS tornado....

Here is a forecast sounding from the RAP that is probably representative of what the QLCS is ingesting. 

 

OK, so it seems like intense QLCS tornadoes are on the table today...

1 minute ago, DanLarsen34 said:

It’s a tough spot for them to be in too. The ceiling on today is incredibly high. 

I don't envy the forecaster seat in these types of events.

13 minutes ago, DanLarsen34 said:

No hint from the SPC that we’ll see an upgrade at any point. Just too much uncertainty at the moment.

Yeah, this seems like it should stay MOD (at least for the next outlook).  Only scenario I see for an upgrade to HIGH is if there is the beginning of an outbreak underway.

Just now, cheese007 said:

Definitely happy that this seems to be trending away from "historic outbreak" territory. Lets hope that trend continues 

I don't think it's trending anywhere right now.  Same story as yesterday.  High ceiling, but potential for bust as well.

FYI, my former PHD advisor's group at CSU runs a 4 km WRF that uses GFS as LBCs.  The simulated radar reflectivity loop can be found here:

http://schumacher.atmos.colostate.edu/weather/real_time_wrf/radar_1km_4km/anim.php

UH tracks:

29 minutes ago, Wmsptwx said:

Saw that...was a bit of a mess. Definitely not a high risk look on HRRR.

I don't know - one could argue that a lot of these are discrete cells, and there are A LOT of UH tracks.  This could indicate an outbreak.