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

NoSnowATL said:
Does the am timeframe lessen this event for Georgia?


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I'm unsure how much it'll negatively impact GA as is also the case in the Carolinas. The environment after sunset on Sunday is nothing short of insane in Georgia & the Carolinas, even if the storm mode is highly linear, we don't see a lot of tornadoes, & our lapse rates aren't quite as steep during the night, this still looks really really bad and the absurd low-level advection of warm/moist air off the Gulf will be the primary contributor to our instability. If anything, the environment looks a wee bit better in the Carolinas than in GA, but it's within the realm of noise & 90-100 knots of deep layer shear coupled with 40+ knots of 0-1 shear, 400-500 0-1 SRH, & surface based CAPE between 500-1000 j/kg is definitely on the higher end of the parameter space even for a big outbreak.
 
Webberweather53 said:
I'm sorry but keeping the Carolinas in the slight risk is a complete joke at this point. No meteorologist in their right mind that's actually looking at the type of environment that's being consistently forecasted over the Carolinas Sunday night into early Monday would conclude there's only a low/slight risk of straight line wind damage and tornadoes. I get the whole ordeal wrt their forecasts ending near 12z but, I think the SPC is really out to lunch on the overall threat level in the Carolinas.
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Given the time of day and evolutionary processes of what occurs upstream first is procluding upgrades at this time I'm certain.
Marine influences even with strong dynamic setups still tend to limit coastal SC severe weather (best SVR Coastal Counties wise tend to come from trajectories moving W to E or NW to SE typically).

However with that being said, LLJ maximization with CAPES ~}1000 J/KG throw climatology out the window.
I think upgrades are coming...probably won't be until Sunday morning or Early Sunday afternoon at the latest when the expected turmoil unfolds on Easter Sunday.
I agree that offices in the Carolinas are erring on the side of caution today.
 
Shaggy said:
I pulled this sounding from right at the time the storms are hitting my neck of the woods. Is the SRH levels really gonna be that high and does it matter if its linear and not discrete?
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When you're dealing with linear vs discrete storm modes in an extreme setup like this, you're basically trading a higher threat of straight line damaging winds w/ linear QLCS vs the potential for strong, long-lived tornadoes if we see more discrete storms.

Pick your poison.
 
Webberweather53 said:
When you're dealing with linear vs discrete storm modes in an extreme setup like this, you're basically trading a higher threat of straight line damaging winds w/ linear QLCS vs the potential for strong, long-lived tornadoes if we see more discrete storms.

Pick your poison.
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Does it seem like both can happen in the setup?


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Webberweather53 said:
I'm sorry but keeping the Carolinas in the slight risk is a complete joke at this point. No meteorologist in their right mind that's actually looking at the type of environment that's being consistently forecasted over the Carolinas Sunday night into early Monday would conclude there's only a low/slight risk of straight line wind damage and tornadoes. I get the whole ordeal wrt their forecasts ending near 12z but, I think the SPC is really out to lunch on the overall threat level in the Carolinas.
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THANK YOU! I was just about to post that. Like, what is SPC thinking? Even Brad P. who normally leans conservative is worried about the increasing tornado threat. I have a feeling that the warm front will add even more energy and the possibility of some sig tornadoes. If we are still in the slight risk come tomorrow, I will lose some respect for SPC. Need to get people prepared.
 
Dawgdaze22 said:
Does it seem like both can happen in the setup?


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Absolutely, it's just that when you have linear storm modes, the cold pools from individual storms merge and make it more difficult to generate stronger, longer-lived tornadoes, the warmer your rear flank downdraft, the better (for tornadoes) because it's easier to tilt & stretch the relatively warmer rain cooled air. Also looking at things like DCAPE in your sounding can be important in this regard
 
ryan1234 said:
THANK YOU! I was just about to post that. Like, what is SPC thinking? Even Brad P. who normally leans conservative is worried about the increasing tornado threat. I have a feeling that the warm front will add even more energy and the possibility of some sig tornadoes. If we are still in the slight risk come tomorrow, I will lose some respect for SPC. Need to get people prepared.
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Latest attendant outlook from SPC for Sunday is a great read and outlines the possible scenarios which is why no upgrades came for Sunday and Monday.
 
Webberweather53 said:
When you're dealing with linear vs discrete storm modes in an extreme setup like this, you're basically trading a higher threat of straight line damaging winds w/ linear QLCS vs the potential for strong, long-lived tornadoes if we see more discrete storms.

Pick your poison.
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I was just curious because I'm not sure I've ever seen our SRH at 500 to 600 m2 s2 here before.
 
ryan1234 said:
THANK YOU! I was just about to post that. Like, what is SPC thinking? Even Brad P. who normally leans conservative is worried about the increasing tornado threat. I have a feeling that the warm front will add even more energy and the possibility of some sig tornadoes. If we are still in the slight risk come tomorrow, I will lose some respect for SPC. Need to get people prepared.
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Have to agree with earlier sentiment here that the threat level will eventually increase & I'm guessing that the lower threat is being assumed for now because there's uncertainty w/ timing because SPC outlooks are from 12z-12z. Even still, people should be prepared Sunday Night into the first half of Monday
 
Shaggy said:
I was just curious because I'm not sure I've ever seen our SRH at 500 to 600 m2 s2 here before.
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Yeah, the only other time I've seen it that high aside from tropical cyclones is during April 16, 2011. 100-150 0-1 SRH is typically what you need to get tornadoes if the storms are ingesting perfectly streamwise vorticity (i.e. critical angles = 90 deg), anything above that is gravy because the storms don't have to be ingesting perfectly streamwise to produce tornadoes and the ceiling is higher for stronger tornadoes. Once you start seeing 0-1 SRH values up to 250-300 m2/s2, that's usually sufficient for a large-scale tornado outbreak all else considered, values of 500-600 like we're seeing here is just plain stupid & in the upper echelon of tornado outbreaks.
 
I love some good Euro wind maps. Brings a strip of 90+ mph wind gusts through NC Minday morning, within an overall background state of gusts over 40 for 9+ hours. Lolz
 
90+ only achievable in places like Boone & West Jefferson. Which is still note worthy low elevations compared to it usually being limited to Michell or Grandfather mtns.
 
Just for some perspective again, here's the distributions of supercell & sig tor composite parameters, effective helicity, effective shear, & LCL for about 20 strong (EF2+) tornado cases in central NC.

There's no denying that this setup is towards the upper end of the parameter space even for those cases.



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Screen Shot 2020-04-11 at 3.06.43 PM.png
 
Webberweather53 said:
Have to agree with earlier sentiment here that the threat level will eventually increase & I'm guessing that the lower threat is being assumed for now because there's uncertainty w/ timing because SPC outlooks are from 12z-12z. Even still, people should be prepared Sunday Night into the first half of Monday
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Part of them leaning this way, and this is pure speculation at this point, is that it has been a LONG time since we had a threat of a tornado outbreak in the western Carolina's. Eastern NC had one in 2011, but besides that, there are only a few more that come to mind in our area. 1989 and I wan to say 1994? It was a Palm Sunday one, I believe. I just think they are waiting before they pull the "historic card" from fear of busting. But I just don't see how we bust tomorrow. I don't see the wedge holding on during the whole event, and that's normally been our saving grace in the past. Timing is also irrelevant given this setup. And like you said, I think this area might end more primed than GA, to some degree.
 
ryan1234 said:
Part of them leaning this way, and this is pure speculation at this point, is that it has been a LONG time since we had a threat of a tornado outbreak in the western Carolina's. Eastern NC had one in 2011, but besides that, there are only a few more that come to mind in our area. 1989 and I wan to say 1994? It was a Palm Sunday one, I believe. I just think they are waiting before they pull the "historic card" from fear of busting. But I just don't see how we bust tomorrow. I don't see the wedge holding on during the whole event, and that's normally been our saving grace in the past. Timing is also irrelevant given this setup. And like you said, I think this area might end more primed than GA, to some degree.
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Timing imo shouldn't be seen as a necessary prerequisite in this setup, if anything, it's more like adding insults to what will already be very severe injuries.
 
ryan1234 said:
NWS ATL did. I think it's kinda premature, but that's my opinion. Not that they are wrong, given current modeling. But so much can and will change.
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I think they are trying to get the attention of the +7mm people who live in their CWA and are only paying attention to Covid-19 stories right now. Plus what’s historic for NGA is a lot different than what’s historic for MS/AL. They have a high bar to clear for that!
 
Something to also keep in mind besides the Tornado threat. Most areas will probably see 1-2 inches of rain during the day Sunday. Which will saturate the ground enough. With some of these models bringing 50-60+ mph wind gusts even without thunderstorms. We could see thousands of power outages across a wide spread area of the southeast.


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Ron Burgundy said:
I think they are trying to get the attention of the +7mm people who live in their CWA and are only paying attention to Covid-19 stories right now. Plus what’s historic for NGA is a lot different than what’s historic for MS/AL. They have a high bar to clear for that!
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Hmm... that's actually a great observation. And if that's the case, some of the other NWS offices are doing other area's a disservice.
 
Webberweather53 said:
Just for some perspective again, here's the distributions of supercell & sig tor composite parameters, effective helicity, effective shear, & LCL for about 20 strong (EF2+) tornado cases in central NC.

There's no denying that this setup is towards the upper end of the parameter space even for those cases.



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Curious looking at that map. Has there never been an EF5 in that state?
 
Jessy89 said:
Something to also keep in mind besides the Tornado threat. Most areas will probably see 1-2 inches of rain during the day Sunday. Which will saturate the ground enough. With some of these models bringing 50-60+ mph wind gusts even without thunderstorms. We could see thousands of power outages across a wide spread area of the southeast.


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Hopefully any power outages won’t last to long because a lot of people have freezers and fridges full of food from stocking up while on shelter in place.
 
Cadi40 said:
Models still continue to enhance STP and activity in general in and around the Charlotte region, should I be concerned?
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Yes. We ALL need to be weather aware. And since we a lot of us lack any outdoor warning systems, we need to make sure our phones are charged and that we have other ways to get warnings.
 
ryan1234 said:
THANK YOU! I was just about to post that. Like, what is SPC thinking? Even Brad P. who normally leans conservative is worried about the increasing tornado threat. I have a feeling that the warm front will add even more energy and the possibility of some sig tornadoes. If we are still in the slight risk come tomorrow, I will lose some respect for SPC. Need to get people prepared.
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You are right about Brad P. I just had a chance to watch his Vlog from this morning and he is very concerned about this. I honestly haven’t seen him this certain of something since right before the flooding from Hurricane Florence
 
Webberweather53 said:
I'm sorry but keeping the Carolinas in the slight risk is a complete joke at this point. No meteorologist in their right mind that's actually looking at the type of environment that's being consistently forecasted over the Carolinas Sunday night into early Monday would conclude there's only a low/slight risk of straight line wind damage and tornadoes. I get the whole ordeal wrt their forecasts ending near 12z but, I think the SPC is really out to lunch on the overall threat level in the Carolinas.
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Good call. Their new wording is a little worrisome for eastern NC

Trend has been for a slower progression of broken line of storms
that should extend from western VA southward through the central
Carolinas by 12Z Monday. This should allow greater downstream
destabilization across the eastern Carolinas as upper 60s F
dewpoints advect inland from the Gulf stream, along with possibility
of modest diabatic heating of the boundary layer supporting up to
1500 J/kg MLCAPE. Wind profiles with 50+ kt effective bulk shear and
large 0-1 km hodographs will support embedded supercells and bowing
linear segments with damaging wind and tornadoes the main threats
from morning into early afternoon.
 
Matthew70 said:
Curious looking at that map. Has there never been an EF5 in that state?
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Unless revisions downgraded, there was an operationally categorized F5 that intensified in NC from the F4 that struck Bennettsville, SC causing major casualties and damage on March 28th, 1984. One of the most violent and deadly outbreaks in Carolinas history
 
Just saw NWS post this on their FB page... umm, why do they have a picture of hail and lightning when tornadoes and damaging winds are the main threats? I understand it's probably something that they post during any outbreak, but you would think they might be a little more willing to make a new, updated checklist highlighting what is most likey. Just seems kinda silly.


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Stormsfury said:
Unless revisions downgraded, there was an operationally categorized F5 that intensified in NC from the F4 that struck Bennettsville, SC causing major casualties and damage on March 28th, 1984. One of the most violent and deadly outbreaks in Carolinas history
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Pitt county tornado on that day had winds at 205mph I believe.
 
ryan1234 said:
Just saw NWS post this on their FB page... umm, why do they have a picture of hail and lightning when tornadoes and damaging winds are the main threats? I understand it's probably something that they post during any outbreak, but you would think they might be a little more willing to make a new, updated checklist highlighting what is most likey. Just seems kinda silly.


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That is a premade graphic they release commonly, it doesn't have anything to do with the expected threats.
 
ryan1234 said:
Just saw NWS post this on their FB page... umm, why do they have a picture of hail and lightning when tornadoes and damaging winds are the main threats? I understand it's probably something that they post during any outbreak, but you would think they might be a little more willing to make a new, updated checklist highlighting what is most likey. Just seems kinda silly.


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Looks like it might could be a spinner chasing that lighting ... ?
 
The 3km NAM's CAPE and thermo profiles busted horribly today in Texas (on the low side), makes me cringe to think about the possibility that it's underselling the CAPE & low-level lapse rates here in NC. Also, the amount of crapvection forecast by the CAMs has been severely oversold thus far.
 
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