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Severe WX Severe Weather Event April 13-14, 2019

NWS Peachtree City as of this morning has damaging winds as primary threat with “a few tornadoes can’t be ruled out”. Is there a limiting factor making a tornado threat less obvious for North Georgia? Maybe storms along the cost robbing us of instability?
 
Richardjacks said:
Yes, I know...but for April, typically you need higher CAPE vs wintertime events. It could end up being higher than what is shown, but for a mid April event, I just don't find it impressive enough for a Enhanced threat.
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That assumes Springtime dynamics and upper level support however. The fact that the closest analog match is 11/1992 tells me this is not a typical springtime system in terms of its dynamics..
 
rolltide_130 said:
That assumes Springtime dynamics and upper level support however. The fact that the closest analog match is 11/1992 tells me this is not a typical springtime system in terms of its dynamics..
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That is very true and something I didn't think of... A cool season analog on a Springtime event typically is not good. While I do think there is a chance of something significant happening in Alabama, perhaps over a small area, I also want to be careful and not sound the alarm on something that is questionable. There are still some questions as to timing...which could have large implications on the available CAPE...especially if storms arrive later vs. earlier than expected. I have seen these type of setups crawl much slower than expected.
 
1324


I have go with Richard on this one. Still have time but significant lack cape is concerning to me as well. The timing is not great for West Al. Ive seen plenty of strong dynamics and underwhelming thermos Forecasted Convective Amplification Deficiency. But it can go the other way around too. 500 - 750 of cape in the height of severe wx season is reason enough for me to leave it at a slight risk. Simulated radar also shows a narrow band of storms moving through. (yes I know its partially broken) Slight risk is spot on right now lets see how it evolves and adjust accordingly.
 
Here are two things we have to watch for in Alabama-
#1. Let's say the line is moving much slower than expected and is only a line of broken supercells, that is going to cause much less contamination of the warm sector for storms later in the morning...as the main forcing moves in closer, which would cause lapse rates to steepen and while shear is still strong...there is a morning-midday window for that to happen.
#2. Let's say the line moves in quicker and is a fairly solid line of storms, it will cap into the limited CAPE and then slow down a bit with time...causing the warm sector to become messy and greater CAPE doesn't line up with the shear as it just doesn't have time to build in.

Yesterday's 18z NAM suggested to me #1 is possible, or least closer to #1, than #2, which caused me more concern. Most of the model guidance has been suggesting #2.

If you just take the line itself moving in during the pre-dawn hours, sure there may be a tornado or two, but I think the threat is fairly limited due to CAPE/lapse rates....if it slows down or doesn't really behave like a line/or line of supercells and does little to the warm environment, then we have a much larger threat window.
 
darkskys25 said:
View attachment 1324


I have go with Richard on this one. Still have time but significant lack cape is concerning to me as well. The timing is not great for West Al. Ive seen plenty of strong dynamics and underwhelming thermos Forecasted Convective Amplification Deficiency. But it can go the other way around too. 500 - 750 of cape in the height of severe wx season is reason enough for me to leave it at a slight risk. Simulated radar also shows a narrow band of storms moving through. (yes I know its partially broken) Slight risk is spot on right now lets see how it evolves and adjust accordingly.
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The slight risk has NOTHING to do with the dynamics and A LOT to do with the timing of when the SPC starts and stops their outlooks at 12z. Read Jason Simpson’s Facebook post for info about that.
 
Kory said:
The slight risk has NOTHING to do with the dynamics and A LOT to do with the timing of when the SPC starts and stops their outlooks at 12z. Read Jason Simpson’s Facebook post for info about that.
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Yes, but slight risk is outlined for both time periods, Saturday and Sunday...Day 2 and Day 3- that's what Jason was alluding to (I saw his post). The only ENH risk in Alabama is in east Alabama.
 
warneagle said:
12z HRRR is absolutely vicious for tomorrow afternoon. Wow. Several supercells in that environment is not what you want to see.View attachment 1325
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Good lord. 12Z 3K NAM has at least one nasty streak of UH across the ARLATEX tomorrow afternoon/evening.

HRRR has oversold a couple events this year but did pretty well with 3/3. Even half of what it shows would be bad.
 
rolltide_130 said:
That assumes Springtime dynamics and upper level support however. The fact that the closest analog match is 11/1992 tells me this is not a typical springtime system in terms of its dynamics..
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I'm assuming it's OK to ask these questions ahead of the event so here goes:

I've looked online, including at WeatherPrediction, but can't seem to find a suitable explanation for "Upper Level Support"........can you elaborate a bit on what that means and how it impacts the environment?
 
Jimruns said:
I'm assuming it's OK to ask these questions ahead of the event so here goes:

I've looked online, including at WeatherPrediction, but can't seem to find a suitable explanation for "Upper Level Support"........can you elaborate a bit on what that means and how it impacts the environment?
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Upper level support is talking about what's happening around 12000 feet and higher. You can have as surface cold front, but that is only at the surface. In this case, the upper support is caused by a deepening upper low causing temps aloft to lower and creating more instability...also it is causing divergence aloft which helps to sustain updrafts Upper support can mean several different things but all are aloft and not near the ground.
 
Richardjacks said:
Upper level support is talking about what's happening around 12000 feet and higher. You can have as surface cold front, but that is only at the surface. In this case, the upper support is caused by a deepening upper low causing temps aloft to lower and creating more instability...also it is causing divergence aloft which helps to sustain updrafts Upper support can mean several different things but all are aloft and not near the ground.
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Thank you Richard.....
 
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