January 10-11, 2020 — Severe Weather Threat Deep South - Archived Storm Threads - 33andrain Weather Discussion Community Jump to content
Adam

January 10-11, 2020 — Severe Weather Threat Deep South

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   An intense mid/upper trough over the Four Corners and northwest Mexico early on Friday
   will eject eastward into the southern Plains by 12z Saturday. At the
   surface, low pressure will develop over TX and shift east/northeast
   toward central AR by 12z Saturday. Ahead of the low, rich Gulf
   moisture will stream northward across eastern TX/OK and expand
   eastward across the lower MS Valley and Gulf Coast states through
   Saturday. 60s F dewpoints are forecast to extend as far north as the
   lower OH Valley by Saturday morning, with upper 60s to near 70s
   dewpoints over parts of the Arklatex on Friday into much of
   LA/MS/AL/GA on Saturday. This anomalously rich and broad warm sector
   will reside beneath a 50-70 kt southerly low level jet and 80+ kt
   southwesterly 500 mb jet streak. While some questions remain over
   how pristine the warm sector ahead of the surface low and cold front
   will remain, especially on Saturday, this kinematic and
   thermodynamic parameter-space will support severe thunderstorms
   capable of all severe hazards from the Arklatex into the TN
   Valley/Gulf Coast states Friday and Saturday.

day4prob.gif

day5prob.gif

 

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This is quite the setup for early January. Perhaps the most impressive aspect of this is the northward surge of moisture as both the Euro and GFS indicate dews into the lower 60's perhaps into the OV. That's a pretty significant vort max and jet streak moving into what has potential to become a perhaps moderately unstable airmass. Clouds and warm sector precip may limit instability, however, given the presence of some EML air there is the potential forecast models are overdoing clouds/warm sector precip...and given the rich llvl theta-e air any more heating than advertised and instability will sky rocket. 

 

At least right now this looks like we could see a widespread damaging wind event with several QLCS tornadoes. Discrete supercells/tornadoes are certainly possible, however, the flow may be a bit too unidirectional...I'm sure there will be some directional aspect in the lowest few thousand feet but I would maybe want to see more overall turning in the lowest 5,000 feet to think a bigger outbreak. 

 

I'm actually a little surprised the 30% contour doesn't go farther south into southeastern TX...actually could be a spot for discrete supercells...especially early on in the game. 

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The overnight forecast models I think became a bit more impressive with this...especially eastern TX into AR/LA. That is some EML to go along with very strong wind shear, vigorous s/w energy, and potential for > 1500 J/KG of MLCAPE and several hundred J of 0-3km CAPE...maybe even 100-150 J of 0-1km CAPE. A couple intense tornadoes certainly possible 

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The 12z runs really have me concerned from eastern TX into LA...starting to get signals too for discrete warm sector convection. 12z NAM/GFS bukit for IAH in particular is extremely ominous with an overlap of large CAPE and shear. NAM indicating > 500 J of 0-6km CAPE with well over 1000 J MLCAPE and shear > 45 m/s...not good. 

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Was wondering when I'd see a thread get started. This event, ever since I jumped onto it last Satuday, has had massive potential...the Super Tuesday analog popped as early as Monday. 

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Another thing to remember: no matter WHAT the dominant storm mode is (I favor a nasty QLCS with several embedded tornadoes and potential high-end wind damage with potential for cells out ahead) this is a cool season event, and not a ton of CAPE needs to be realized for this to be a major event.

 

The nighttime Alabama tornadoes on Super Tuesday only needed 200-400.

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1 minute ago, Crossbowftw3 said:

Another thing to remember: no matter WHAT the dominant storm mode is (I favor a nasty QLCS with several embedded tornadoes and potential high-end wind damage with potential for cells out ahead) this is a cool season event, and not a ton of CAPE needs to be realized for this to be a major event.

 

The nighttime Alabama tornadoes on Super Tuesday only needed 200-400.

Wow. Only 200-400 JKG, that is news to me

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1 minute ago, Logan Giles said:

Wow. Only 200-400 JKG, that is news to me

Exceptional shear values were present during the night portion of that event, mind you. Exceptional shear exists once more here--if there's tornadic cells in an undisturbed warm sector out ahead of the line you're going to have a space favorable for strong tornadoes.

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3 minutes ago, Crossbowftw3 said:

Another thing to remember: no matter WHAT the dominant storm mode is (I favor a nasty QLCS with several embedded tornadoes and potential high-end wind damage with potential for cells out ahead) this is a cool season event, and not a ton of CAPE needs to be realized for this to be a major event.

 

The nighttime Alabama tornadoes on Super Tuesday only needed 200-400.

With a background elevated mixed layer & some of the hodographs depicted, this event has great potential of producing. 

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1 minute ago, Crossbowftw3 said:

Exceptional shear values were present during the night portion of that event, mind you. Exceptional shear exists once more here--if there's tornadic cells in an undisturbed warm sector out ahead of the line you're going to have a space favorable for strong tornadoes.

Gotta imagine any storms ahead of the QLCS will have a solid chance of being tornadic. Untapped warm sector with 40-50 its of shear 

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4 minutes ago, Logan Giles said:

Gotta imagine any storms ahead of the QLCS will have a solid chance of being tornadic. Untapped warm sector with 40-50 its of shear 

 

5 minutes ago, CCB! said:

With a background elevated mixed layer & some of the hodographs depicted, this event has great potential of producing. 

This definitely has potential to produce in a big way. Exceptional SRH exists with the line to get numerous spinups, some undoubtedly strong (like the EF2 closer to our neck of the woods Halloween night, would likely be embedded in a larger swath(s) of wind damage), and if cells get ahead of the line, a space favorable for strong tornadoes should and likely will, exist. I've found 400-800 ms2 of helicity on soundings, which would be bonkers on a springtime event...and extreme for a wintertime event.

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This potential event serves as a great reminder to people in the south that severe weather can happen at any time of year...even large outbreaks. Severe weather in January is relatively uncommon, but no one is invincible from severe wx even in January

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You certainly don't need a ton of CAPE in these cool season events when you have tremendous forcing/shear present. However, sometimes shear can be just too much and that can mitigate potential somewhat...but that shouldn't be the case here. Models hinting at 1500+ J/KG of MLCAPE is extremely, extremely significant given these other parameters...hell even if setups with lesser shear 1500+ MLCAPE isn't too bad. One thing to really focus on too in terms of at least instability is 0-3km CAPE...given the robust shear/turning in that level you get robust CAPE in that level given the LCL's...something is bound to produce.

 

what is extremely scary here is the best parameters look to be lining up after dark.  

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