Severe WX Severe Weather Threat 11/5-11/7 (5 Viewers)

Taylor Campbell

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One thing all models seem to show is the shear, and instability juxtaposed well over such a wide area. There's going to be severe left, and right.
 

Fred Gossage

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There are some significant large-scale similarities between the general Euro/GFS/FV3/Ensembles/NAVGEM setup for the early next week system and the system back on 11/10/2002. I distinctly remember on the early versions of this very forum in the days leading up to that outbreak, Brad Travis starting to hit 11/10/2002 very hard starting five days out. The interesting note about that is, that far out, it looked like it would be a Saturday afternoon threat for north Alabama. It ended up digging the trough a little deeper than shown that far out (but still very low amplitude) and it slowed enough that it was a Sunday afternoon and night threat for MS/AL/TN.

The models, especially the GFS, show an 85-90+ kt 500mb jet streak moving into the base of the trough from the left side. When stronger winds move into a trough, the trough digs. That is very basic synoptic meteorology. However, they don't dig the trough at all with that being the case. The same thing happened in the models days ahead of that potential analog case. There is precedent here for the trough to end up being still low-amplitude but with the base a little deeper and lower heights further southward... and for the system to slow down so that it may end up being a midday/afternoon/evening threat on Tuesday for areas as far west as I-55 or the Mississippi River.
 

andyhb

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00z GFS definitely appears to be a shift towards the more ominous solutions as it does not split the lead wave into two parts and leave one further south to suppress moisture return.

The shear with the primary system is high end, especially when you account for the fact that the GFS is probably not handling the low level wind response very well.
 

Taylor Campbell

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Yes, the GFS is more ominous. A big uptick in supercell composite numbers over a large area. I'm interested to see its ensembles. I believe there will be some more robust members, and future runs will continue to get worst.
 
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Fred Gossage

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Every. single. model. tonight has trended toward a stronger system that digs a touch further south... and toward a more ominous situation over a very large area of the OH/TN/MS Valleys and classic Dixie Alley. And with a trend toward the system's trough axis being a little sharper, and the low track being a little more NNE than ENE, you are likely going to start seeing a slowing trend with time...
 

Timhsv

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Game on guys.....

Matt hits it pretty serious.


AFDBMX
Area Forecast Discussion
National Weather Service Birmingham AL
400 AM CDT Fri Nov 2 2018



Edited for emphasis on Monday night/ Tuesday threat:

Models are coming into agreement on a potentially dangerous setup Monday night into
Tuesday morning across a large area which includes Alabama. The GFS and ECMWF are in good agreement with the evolution of the
synoptic pattern, showing a low-amplitude shortwave taking on a negative tilt Monday night to our northwest. This pattern has the
look of a classic severe weather outbreak and would support a rapidly deepening surface low tracking toward the Great Lakes with
significant pressure falls extending southward into Alabama. With dewpoints rising into the upper 60s to perhaps 70F, instability
appears more than sufficient for deep convection within a very highly sheared environment. Taken at face value, the ECMWF shows
semi-discrete supercells capable of producing long-track, significant tornadoes across the northern half of our forecast

area on Tuesday morning. The HWO will be updated to include a moderate confidence threat for tornadoes and damaging winds across
the entire forecast area. With this threat still around 96 hours out and models subject to change, we will refrain from going all
in on the potential for a tornado outbreak.

87/Grantham
 
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Fred Gossage

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HWO.gif


000
FLUS44 KBMX 020909
HWOBMX

Hazardous Weather Outlook
National Weather Service Birmingham AL
409 AM CDT Fri Nov 2 2018

ALZ011>015-017>050-031215-
Marion-Lamar-Fayette-Winston-Walker-Blount-Etowah-Calhoun-Cherokee-
Cleburne-Pickens-Tuscaloosa-Jefferson-Shelby-St. Clair-Talladega-
Clay-Randolph-Sumter-Greene-Hale-Perry-Bibb-Chilton-Coosa-Tallapoosa-
Chambers-Marengo-Dallas-Autauga-Lowndes-Elmore-Montgomery-Macon-
Bullock-Lee-Russell-Pike-Barbour-
409 AM CDT Fri Nov 2 2018

This Hazardous Weather Outlook is for the counties served by the
National Weather Service office in Birmingham.

.DAY ONE...Outlook through Tonight.

Areas of fog are expected to develop late tonight into early Saturday
morning. Visibility could drop to less than one mile in some areas.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Areas of fog may linger through 9 AM on Saturday. Visibility could
drop to less than one mile in some areas.

A strong storm system may bring a threat for tornadoes and damaging
winds to all of Central Alabama late Monday night into Tuesday
morning. This has the potential to become a widespread and significant
event and will be monitored closely.


.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management may be needed
late Monday night into Tuesday morning.

$$
 

Kory

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We are now within 100 hours of the event. Models are pretty locked in and I just don't see enough time for wholesale synoptic changes. No subtropical jet influence. Nasty jet streak rounding the base of the trough. Broad base taking on a negative tilt that isn't enough forcing to muddle the warm sector. And, not to mention, enough advective destabilization despite this arriving in the overnight hours. At face value, we're talking ~1000-1500 J/KG CAPE in the dead of night...
 
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Xenesthis

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It really doesn’t seem like much can get in the way at this point. This really looks like this could go down in history books as one of the worst fall outbreaks. Does anyone else see the possibility of the slowing a bit?
 

NWMSGuy

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Overall how do you guys think this threat is shaping up for the Mid-South region? Fairly large area already in an Enhanced Risk for Day 4 with Memphis being on the northern extent.
 
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Richardjacks

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Systems like these do have a tendency to slow down, especially given how the trough will undergo such a change with the powerful jet streak. However, that shift from neutral to negative will induce a progressive mode at some point but it could be late in the event for Alabama.
 

Bama Ravens

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BMX AFD:

The shortwave on Sunday night will serve as a primer wave for the next system developing to our west on Monday. A wide area of rich moisture will be lurking near the Gulf Coast, poised to move inland Monday afternoon and evening as wind fields respond to a shortwave entering the Southern Plains. Models are coming into agreement on a potentially dangerous setup Monday night into Tuesday morning across a large area which includes Alabama. The GFS and ECMWF are in good agreement with the evolution of the synoptic pattern, showing a low-amplitude shortwave taking on a negative tilt Monday night to our northwest. This pattern has the look of a classic severe weather outbreak and would support a rapidly deepening surface low tracking toward the Great Lakes with significant pressure falls extending southward into Alabama. With dewpoints rising into the upper 60s to perhaps 70F, instability appears more than sufficient for deep convection within a very highly sheared environment. Taken at face value, the ECMWF shows semi-discrete supercells capable of producing long-track, significant tornadoes across the northern half of our forecast area on Tuesday morning. The HWO will be updated to include a moderate confidence threat for tornadoes and damaging winds across the entire forecast area. With this threat still around 96 hours out and models subject to change, we will refrain from going all in on the potential for a tornado outbreak.
 
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Overall how do you guys think this threat is shaping up for the Mid-South region? Fairly large area already in an Enhanced Risk for Day 4 with Memphis being on the northern extent.
fairly confident you see SPC expand the 30 percent area in tomorrow mornings outlook... which will then be 3 day outlook... cause of timing coming in bit slower... allo better instability to get pulled further north.... at face value now... mid south region is under the gun late monday overnight monday... which is also bad... cause the lower level jet will really amp up
 

Weatherphreak

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Hate that this could be a early morning event. I remember Super Tuesday a lot of folks went to bed in North Alabama thinking the severe threat had busted and then you had the Lawrence county EF3-4? and the Rosalie EF3-4? That hit between 4am-6am. Would much rather see a midday event.
 
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Hate that this could be a early morning event. I remember Super Tuesday a lot of folks went to bed in North Alabama thinking the severe threat had busted and then you had the Lawrence county EF3-4? and the Rosalie EF3-4? That hit between 4am-6am. Would much rather see a midday event.
It may trend toward a late morning event over the next few days.

But as you stated, the two Alabama EF-4 tornadoes occurred in the dead of night, resulting in 4 fatalities. The Lawrence/Morgan county tornado lifted shortly before entering Decatur.
 
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Xenesthis

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Looking at some of the GFS runs it seems as though the GFS is trying to slow down the system so I’m here. I am in Southern middle Tennessee and it is showing the tornadic weather between 12 and 6 PM on Tuesday. I wonder if this wind of verifying?
 

amp1998

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Looking at some of the GFS runs it seems as though the GFS is trying to slow down the system so I’m here. I am in Southern middle Tennessee and it is showing the tornadic weather between 12 and 6 PM on Tuesday. I wonder if this wind of verifying?
Yeah it's definitely possible that this slows down to a daytime event as well as a nighttime event.
 

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