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Archive March 18-20th, 2018 Severe Weather

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Xenesthis

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Yep I feel confident they will.

Sent from my H1611 using Tapatalk

I wouldn’t be surprised to see an area of moderate let alone enhanced. It really just depends on what model comes closest to verifying.
 
X

Xenesthis

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Haven't had time to look at details but it appears the 12z name is slightly backing off low level shear on 12z run.

Enough to make a large difference? Last NAM guidance had a PDS TOR reading for my area
 

Fred Gossage

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Haven't had time to look at details but it appears the 12z name is slightly backing off low level shear on 12z run.

Some of it is with feedback from a surface low that magically develops much further east in middle TN by afternoon... previous runs had been doing this too. The NAM looks like it is trending toward correcting this, though. But even with that the case, the 12z run of the 3 km NAM... which uses the 12km for its synoptics... is doing this... WITH the south-southwest to south surface winds and the feedback issues with the low...

ehi03.us_se.png


ehi01.us_se.png


stp.us_se.png


And the forecast soundings with the virtual temperature correction to the thermodynamic profile then show 1 km EHIs that are as high as 5-6 near Birmingham...

nam4km_2018031712_057_33.79--86.82.png


....along with the sickle hodographs that have the rightward kink in the lowest 1 kilometer...

The 3 km has also, since it has gotten within range the past couple of runs, had a 50 kt 850mb jet from 18Z Monday onward.

SREF might peak your interest also. 70% chance that the STP exceeds 3. 30-49.999% percent chance it exceeds 5...
 

Richardjacks

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Some of it is with feedback from a surface low that magically develops much further east in middle TN by afternoon... previous runs had been doing this too. The NAM looks like it is trending toward correcting this, though. But even with that the case, the 12z run of the 3 km NAM... which uses the 12km for its synoptics... is doing this... WITH the south-southwest to south surface winds and the feedback issues with the low...

ehi03.us_se.png


ehi01.us_se.png


stp.us_se.png


And the forecast soundings with the virtual temperature correction to the thermodynamic profile then show 1 km EHIs that are as high as 5-6 near Birmingham...

nam4km_2018031712_057_33.79--86.82.png


....along with the sickle hodographs that have the rightward kink in the lowest 1 kilometer...

The 3 km has also, since it has gotten within range the past couple of runs, had a 50 kt 850mb jet from 18Z Monday onward.

SREF might peak your interest also. 70% chance that the STP exceeds 3. 30-49.999% percent chance it exceeds 5...
Thanks Fred, I wish had more time today to look closer...maybe later this afternoon I will...not looking good.
 

Kory

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I'm just going to clarify...this event will not bust because of the MCS, which models have pushing through Central Alabama between 12-4am Monday morning. It wouldn't surprise me to see a severe wx threat out of that as well.

Really, it is going to come down to the surface to 850mb winds. Those will make or break the tornado threat.
 
Last edited:

rolltide_130

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The 18z NAM run definitely trended more impressive than the 12z run did.. this is going back in the other direction.

Near Huntsville..

nam_2018031718_051_34.67--85.89.png
 
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Idk if you can call a change from one run to the next a "trend," more like typical run to run variability. I'd really need to see the globals slow the system down a bit and get more in line with the NAM's synoptics.
 
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