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LithiaWx

3/19/18 Dixie Alley severe outbreak

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Some wrote it off early. As almost always happens, the early "marginal" turns to "slight" and now it has reached "enhanced." It wouldn't surprise me if it goes to "moderate" by tonight.

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1 hour ago, kperk014 said:

Some wrote it off early. As almost always happens, the early "marginal" turns to "slight" and now it has reached "enhanced." It wouldn't surprise me if it goes to "moderate" by tonight.

This is the worst probability scale in the entire NWS. Millions of people getting info over the radio would have no idea whether "marginal" or "slight" gave the higher risk of severe weather. Many wouldn't know if  they saw the map. That doesn't even factor in the approximately 50% that can't define the word "enhanced".

Low, medium, high. Clear, concise, done.

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35 minutes ago, jburns said:

This is the worst probability scale in the entire NWS. Millions of people getting info over the radio would have no idea whether "marginal" or "slight" gave the higher risk of severe weather. Many wouldn't know if  they saw the map. That doesn't even factor in the approximately 50% that can't define the word "enhanced".

Low, medium, high. Clear, concise, done.

I feel like many local TV mets already do this on their own in their morning and evening broadcasts. Usually verbalize and explain the risk-level as those three you listed. 

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If you want to believe the NAM and this morning's other CAM solutions, tomorrow looks like a Dixie alley special. NAM is particularly ominous over quite a large area. Seems to me like a day where we get a couple/few dominant supercells that produce several tornadoes (possibly strong/long-tracked). But not likely a major/significant tornado outbreak, should be spatially constrained to mainly northern/north-central Alabama perhaps into southern Tennessee. 

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52 minutes ago, jburns said:

This is the worst probability scale in the entire NWS. Millions of people getting info over the radio would have no idea whether "marginal" or "slight" gave the higher risk of severe weather. Many wouldn't know if  they saw the map. That doesn't even factor in the approximately 50% that can't define the word "enhanced".

Low, medium, high. Clear, concise, done.

... or the word "define!"

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1 hour ago, jojo762 said:

I feel like many local TV mets already do this on their own in their morning and evening broadcasts. Usually verbalize and explain the risk-level as those three you listed. 

OK  And they have to do that over and over, day after day because the scale sucks.

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Nam 3km showing a PDS TOR hazard type...

Tomorrow's severe event is mostly localized to Alabama and there is still some uncertainty to the magnitude of the event. However, as an Alabama resident, if the NAM 3km does verify I'm afraid that the public is unprepared. None of my friends or family are taking tomorrow's severe weather threat seriously. 

badWeather.PNG

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The NAM has been terrible forcasting severe weather events; especially, last year.  Last year there were several days it looked like tornado apocalypse and many of them ended in a bust. It is best to wait till the raw data comes in tomorrow the AM.  I get concerned that we rely to much on models and not old fashion in the dirt meteorology.

 

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FWIW, 00z NAM is looking even more volatile across NW Georgia and Northern AL at first glance.

It holds on to pretty impressive instability across the southern half of Metro Atlanta and Birmingham through Tuesday Morning. 

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Looks to be an interesting day if all goes to plan, but there are a couple of caveats, as there always is. The first and foremost is the cluster of ongoing convection on the LA/MS border spreading eastward. Earlier this evening, it looked as if this would grow upscale and may disrupt moisture and heating for the early part of the day slowing the progress of the moist airmass. However, thunderstorms have apparently failed to organize which would allow the atmosphere to recover quicker in theory. Similarly, any generated cloud cover from this complex could also slow down heating and lead to lower instability. This is slightly more independent of the organization of the complex as well. The next being too much capping, which the 3km NAM advertises in particular. Too much would either elevate storms that were able to form or inhibit them all together. With this though, I feel as if the amount of CINH may help more than it hurts by keeping things more discrete, especially for dixie standards.

The latest HRRR thru 21z tomorrow seems to lean towards the NAM, although at this range, it is probably not worth very much. All in all, I think the biggest inhibitor is currently the tstm complex over LA/MS for the first two reasons I mentioned. If that cluster doesn't affect the setup too much and the NAM/HRRR get their ways, this could be a pretty potent setup. Personally, I am expecting an upgrade to a moderate 15% hatched on the 06z SPC outlook.

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50 minutes ago, NWLinnCountyIA said:

Looks to be an interesting day if all goes to plan, but there are a couple of caveats, as there always is. The first and foremost is the cluster of ongoing convection on the LA/MS border spreading eastward. Earlier this evening, it looked as if this would grow upscale and may disrupt moisture and heating for the early part of the day slowing the progress of the moist airmass. However, thunderstorms have apparently failed to organize which would allow the atmosphere to recover quicker in theory. Similarly, any generated cloud cover from this complex could also slow down heating and lead to lower instability. This is slightly more independent of the organization of the complex as well. The next being too much capping, which the 3km NAM advertises in particular. Too much would either elevate storms that were able to form or inhibit them all together. With this though, I feel as if the amount of CINH may help more than it hurts by keeping things more discrete, especially for dixie standards.

The latest HRRR thru 21z tomorrow seems to lean towards the NAM, although at this range, it is probably not worth very much. All in all, I think the biggest inhibitor is currently the tstm complex over LA/MS for the first two reasons I mentioned. If that cluster doesn't affect the setup too much and the NAM/HRRR get their ways, this could be a pretty potent setup. Personally, I am expecting an upgrade to a moderate 15% hatched on the 06z SPC outlook.

With such strong flow aloft, and a good component of it zonal, the clouds shouldn’t be an issue. 

 

Agree, we are going to see a 15% hatched region and probably 30% hatching for hail. 

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The NAM has been terrible forcasting severe weather events; especially, last year.  Last year there were several days it looked like tornado apocalypse and many of them ended in a bust. It is best to wait till the raw data comes in tomorrow the AM.  I get concerned that we rely to much on models and not old fashion in the dirt meteorology.
 


I never understand these types of posts. You’re telling the board to wait until the day of the event but here you are on here the day before looking at what others are saying.


.

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57 minutes ago, PowellVolz said:

 


I never understand these types of posts. You’re telling the board to wait until the day of the event but here you are on here the day before looking at what others are saying.


.

 

A discussion on this forum about severe weather setups are excellent.  I dont have any qualms about that.  So my comments were in no way a criticism of what happens here.  I am just stating I dont get all that hyped up about the model outputs. In addition I was stating that I think we can become too reliant upon them and forget to use old fashion meteorology. 

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A discussion on this forum about severe weather setups are excellent.  I dont have any qualms about that.  So my comments were in no way a criticism of what happens here.  I am just stating I dont get all that hyped up about the model outputs. In addition I was stating that I think we can become too reliant upon them and forget to use old fashion meteorology. 

Well.... their was a discussion going on about the mods but I don’t see the reasoning in saying the mods are not all was right and we should just wait when we already know this but it’s all we have to go on at that time.


.

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I'm surprised by the lack of activity this morning (as far as rain/storms).

That's a good sign, as there isn't anything to work over the atmosphere and prevent the warm sector from surging back northward a

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2 hours ago, LithiaWx said:

I got moved into the enhanced area.  I’ll be right on the wedge boundary here in Douglas county, GA.  We will see how it goes....

They nudged the enhanced risk area a bit further SE, so now it also includes here up to the entire western half of the Atlanta metro area.

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NAM 3km, Hrrr, HrrrX all showing peek SigTor’s around 6.5-7.5 with much of central AL (Tuscaloosa, Birmingham) with a 4-5 SigTor. Cape values will be 3000+

I’m in Tuscaloosa and the sun is already coming out. Not a good sign... 

When is the SPC going to pull the trigger and upgrade to moderate? Just curious what’s holding them back.

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As was already mentioned they said the moderate risk upgrade will happen at 1630Z.

Several of the CAMS including the HRRRX have some modestly potent UH tracks in TN and northern AL. Might be a risk in GA as well.

qqarJ8Y.png

 

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16 minutes ago, Blitzgunner said:

NAM 3km, Hrrr, HrrrX all showing peek SigTor’s around 6.5-7.5 with much of central AL (Tuscaloosa, Birmingham) with a 4-5 SigTor. Cape values will be 3000+

I’m in Tuscaloosa and the sun is already coming out. Not a good sign... 

When is the SPC going to pull the trigger and upgrade to moderate? Just curious what’s holding them back.

They don't really do out of band updates for moderates. The 12:30 EDT update will have it, and still provide a few hours' warning.

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3 hours ago, LithiaWx said:

I got moved into the enhanced area.  I’ll be right on the wedge boundary here in Douglas county, GA.  We will see how it goes....

I'm in SW Atlanta, I don't even believe there will be a wedge to prevent severe weather this time around.  The warm air advection associated with the warm front is going to be too strong for the usual cool air wedge from the east that protects much of North Georgia.  I believe Metro Atlanta will have to watch this event very closely.  Something very unusual is happening with the warm air advection where even East Alabama around Anniston/Oxford and Gadsden are in the enhanced risk, so this is very tell-taling that this storm system is overriding many geographic factors.

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29 minutes ago, kayman said:

I'm in SW Atlanta, I don't even believe there will be a wedge to prevent severe weather this time around.  The warm air advection associated with the warm front is going to be too strong for the usual cool air wedge from the east that protects much of North Georgia.  I believe Metro Atlanta will have to watch this event very closely.  Something very unusual is happening with the warm air advection where even East Alabama around Anniston/Oxford and Gadsden are in the enhanced risk, so this is very tell-taling that this storm system is going overriding many geographic factors.

I do think you're right in this instance, although here in Gwinnett we're socked in with 59 degrees and misty conditions.  The WAA is pretty potent in this case, but we've all seen this before here in Georgia with the North Georgia storm shield alive and kicking.  Over along the western Alabama border counties it's a whole different story.  I'd be especially concerned in the Floyd, Polk, Haralson and Paulding county areas.

- Buck

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