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4/11/20 - 4/13/20 Severe Weather Outbreak

EV_WS said:
Has anyone seen tweets or posts from @Webberweather53 ?
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No major changes (yet) in my overall thinking for tomorrow here. Strong damaging winds and isolated tornadoes will be the main threat(s) over the Carolinas and this is liable to be a respectable severe event here.

Although many are assuming that storm mode will be linear here based on climo, it doesn't look super clear cut to me once you get east of Greensboro-Charlotte into the eastern piedmont and coastal plain. I definitely lean in the direction of linear modes but there are several possible failure points in maintaining a bonafide QLCS the whole day tomorrow.

Large cyclonically curved hodographs basically the whole way thru the troposphere that’s being modeled consistently across the board inhibits neighboring storm collisions and thus cold pool mergers.

We honestly still don't know how strong diabatically forced rear inflow jet (from mainly stratiform precip) will be in addition to how much the cold pools will be advected by the deep layer shear vector, if it's closer to // wrt the line orientation (doesn't look superb here verbatim atm) that encourages break up into discretes (this is how Apr 16 2011 happened) in addition to the potential for the mountains to disrupt the segment of the QLCS & low level cold pool that enters the Carolinas. The synoptic scale forcing will become less impressive (relatively speaking) after tomorrow morning, as the parent surface low occluded and becomes further removed from the Carolinas & this EML is no joke (& verifying stronger than forecast). It's actually possible some of the storms deteriorate a lot or just die as they enter the piedmont around sunrise, which if some places like RDU & Fayetteville, are sufficiently unstable downstream, could encourage new, discrete cells in the warm sector. Also, many cams are trying to break up the line once it gets to about the US HWY 1 corridor.

The other red flag I see for qlcs maintenance beyond the western piedmont of N.C. is the fact that these storms don't appear to be directly attached to the cold front, rather it's a pre frontal trough.


Even though we'll have respectable DCAPE that will encourage stronger cold pools, this suggests that the downdrafts associated with these storms will be warmer as they literally mix warmer air ahead of the front into the wake of the storms, which doesn't favor continuation of a purely linear mode. Along with other aforementioned variables, warmer downdrafts due to the synoptic-mesoscale character of the storm environment is also a primary contributor to April 16, 2011’s very, very unique storm mode evolution from purely linear to discretes in a matter of a few hours which rarely if ever happens. Almost always it’s going to be the other way around. I think this may be linked to something fundamental about the Carolinas, where the Appalachian mountains block the low level cold air on the leading edge of cold fronts, encouraging disentanglement between the front and storms, and thus being more favorable to discrete supercells.

All this being said, I'm certainly in favor of the qlcs idea over discretes for now, albeit not by much. I personally think the most likely scenario regarding storm mode in the Carolinas is we see a qlcs w/ embedded supercells roll thru at least Charlotte and Greensboro, but we see it devolve into an rather obfuscate semi-discrete mode, with respectable completely broken line segments and multiple clusters of embedded supercells, or basically a linear-discrete hybrid mode.
 
NorthGaWinter4 said:
So Cantore said Georgia won’t see the type of violence that Mississippi saw. So, are we busting on the tornado threat here?
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Can we please not call getting less severe weather and tornadoes a “bust”...no rules against and I don’t want to start any kind of argument. Just a pet peeve of mine I guess. I understand the sentiment when the weather doesn’t turn out as models predict. Maybe someone can come up with a more appropriate term considering the potential damage and injuries that would be averted?
 
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