Weekend Severe Possibilities (2/9-10)

[OKpowdah]

The big consensus among model guidance at this point is that a piece of energy from the trough over the Northwest Pacific will jump to the Gulf of Alaska by Wednesday morning, then drop southeastward into California Thursday night into Friday.

Similar to the last event, there is a weak disturbance in the southern stream that gets ejected out ahead of the trough dropping into the Southwest ... and able to lift northeastward as the polar vortex over southeast Canada retreats poleward. So the result is some moisture return ahead of the disturbance Wednesday and Thursday ... maybe some rain too, but let's not get carried away.

The real differences between the GFS and CMC and ECMWF is with the handling of the individual impulses within the western trough. CMC and ECMWF like swinging the lead impulse into eastern Colorado Saturday afternoon. Amplitude, tilt, and timing of this particular piece of energy will be crucial. At this point, the projected evolution brings a warm front through Oklahoma on Saturday with round 1 of thunderstorm potential, and a surface low developing in eastern CO.

The ECMWF and CMC deepen this surface low into western Kansas Saturday night ... really pretty awesome placement for OK. Euro increases CAPE substantially Saturday night. The cold front catches the dryline sometime Saturday night into Sunday morning for round 2 ... so timing is an issue, but verbatim this would no doubt be a significant overnight event.

The trough continues eastward with that primary upper level impulse sharpening over the southern Plains, and the surface low intensifying across the central Plains to Midwest, introducing severe threats for Sunday and Monday for the Dixie Alley area.

 

 

 

[patrick7032]

Looks like on Saturday...a warm front sets up somewhere in Texas. Notice the low level winds on the soundings for Abilene and Oklahoma City compared to San Angelo. Could be some warm frontal stuff...but will load point soundings when at work tomm. BTW...anyone know why the right edges of the images get "chopped off"...unless you click on them?

[brettjrob]

Looks like on Saturday...a warm front sets up somewhere in Texas. Notice the low level winds on the soundings for Abilene and Oklahoma City compared to San Angelo. Could be some warm frontal stuff...but will load point soundings when at work tomm. BTW...anyone know why the right edges of the images get "chopped off"...unless you click on them?

 

Thanks for posting. I can't believe I'm still too lazy to figure out BUFKIT after all these years as a weenie. I think the right side of the images are cutting off just because your browser window isn't wide enough. You should just be able to scroll over (or maximize the window).

 

I'm still extremely pessimistic on moisture return for Saturday near and N of the Red, but hopefully you manage some good boomers down there, and we all manage a soaking rainfall before the trough exits.

[andyhb]

Several of the 18z GFS ensemble members seem to be hinting at some sort of late ejection (ala the 06z OP this morning) that would give plenty of time for a potentially potent antecedent thermodynamic environment to move into place ahead of the trough. Some of the ones that do eject it later pick it up/phase it with one of the vort maxes diving in from the NW and really bomb the wind fields (ala the 06z run) in all likelihood, which would accordingly have significant implications. I'd still consider it an outlier type of solution, but it's certainly something to monitor, especially since models tend to have a hard time with the speed of the ejecting SW closed lows (and also the GFS going against it's traditional progressive bias).

 

Or course, it staying in the SW could also lead to it becoming a discombobulated mess like some previous runs show, but I'd tend to think that one of these vort maxes has to amplify enough to eventually catch it if it does move far enough east, if it doesn't just eject outright in Euro/CMC style.

[andyhb]

Looking though the 00z suite, the models appear to stay with their respective camps, with the GFS being consistently inconsistent with the evolution of the pattern (each run today was significantly different in it's resolution of this trough). The GGEM and Euro continue to show some potential for both days, initially in Western/Central TX (at least from a quick analysis) on D1, and then the Ozarks/Lower MS Valley on D2. The Ukie is somewhere in between.

[patrick7032]

Thanks for posting. I can't believe I'm still too lazy to figure out BUFKIT after all these years as a weenie. I think the right side of the images are cutting off just because your browser window isn't wide enough. You should just be able to scroll over (or maximize the window).

 

I'm still extremely pessimistic on moisture return for Saturday near and N of the Red, but hopefully you manage some good boomers down there, and we all manage a soaking rainfall before the trough exits.

Yw brett. I'll load some point soundings...(more detailed and accurate than Bufkit) when I'm at the office tomm. I did look at Bufkit tonight...and it's definitely looking more like a Sunday event for Oklahoma and Texas. It did bring instability into OKC (not a ton but enough...~500 but good shear at 6pm)...eastern Texas...and points north and east on Monday. In Texas...on Sunday it basically shows 1200-1800 SBCAPES and LIs -4 to -8...with good shear.

[andyhb]

A check of some of the 12z model suite reveals potentially significant severe weather potential on one or both days now, with the ensembles beginning to come into more agreement as well. I'd still expect some modifications, though, given the difficulty that the models have with these type of scenarios.

 

First off the 12z GFS ensembles at 108:

 

Ensembles at 132:

 

12z GFS OP at 126:

 

132:

 

12z FIM at 126/132 (quite dangerous):

 

12z Euro is possibly after dark on Saturday on the timing (114 hrs).

[brettjrob]

I don't know about sig svr on Saturday, as there's still no sign on either the GFS or Euro of sufficient moisture return before sunset. Instability looks likely confined to deep south TX, where shear is sufficient (not great) but initiation seems questionable. The sole positive I'm seeing in the guidance is that the NAM, through H+84, is less aggressive in shunting moisture southward with the mid/late-week front. It doesn't have the big nor'easter at all like the GFS/Euro, which IMO will be a necessary condition for anything significant Saturday. I never like having to hang my hat on the NAM at this range, though.

[andyhb]

I don't know about sig svr on Saturday, as there's still no sign on either the GFS or Euro of sufficient moisture return before sunset. Instability looks likely confined to deep south TX, where shear is sufficient (not great) but initiation seems questionable. The sole positive I'm seeing in the guidance is that the NAM, through H+84, is less aggressive in shunting moisture southward with the mid/late-week front. It doesn't have the big nor'easter at all like the GFS/Euro, which IMO will be a necessary condition for anything significant Saturday. I never like having to hang my hat on the NAM at this range, though.

 

Overnight Saturday was more what I was thinking.

 

Some really impressive LI's on the 18z GFS for Sunday...

[Stebo]

I don't know about sig svr on Saturday, as there's still no sign on either the GFS or Euro of sufficient moisture return before sunset. Instability looks likely confined to deep south TX, where shear is sufficient (not great) but initiation seems questionable. The sole positive I'm seeing in the guidance is that the NAM, through H+84, is less aggressive in shunting moisture southward with the mid/late-week front. It doesn't have the big nor'easter at all like the GFS/Euro, which IMO will be a necessary condition for anything significant Saturday. I never like having to hang my hat on the NAM at this range, though.

Using GFS instability at this junction is a dangerous assumption especially knowing its bias.

[brettjrob]

Overnight Saturday was more what I was thinking.

 

Some really impressive LI's on the 18z GFS for Sunday...

 

Yeah, Sunday should have some potential now that the GFS is conceding on its former idea of lingering the trough in the SW all weekend. The ejection is fairly sloppy so I doubt low-level shear will be anything to write home about, but severe weather with a tornado or two in the Arklatex wouldn't surprise me.

 

Using GFS instability at this junction is a dangerous assumption especially knowing its bias.

 

That's true in a general sense, but it also depends on the circumstances. The low bias is a major factor when it depicts the synoptic pattern correctly with ample moisture, but severely limits daytime heating (due either to unrealistic cloudcover or convective parameterization) and thereby CAPE. To me, the classic signal for this issue (at least in the Plains) is when there's a huge warm sector with 60-65 F dew points, yet its forecast temperatures at 00z are also 60-65 F right up to the dryline.

 

In this case, though, the GFS simply doesn't indicate sufficient moisture for synoptic reasons -- namely, the antecedent frontal intrusion and downstream features not progressing enough. If dew points north of I-10 are really < 60 F on Saturday, its depiction of minimal instability will likely verify.

[Stebo]

Yeah, Sunday should have some potential now that the GFS is conceding on its former idea of lingering the trough in the SW all weekend. The ejection is fairly sloppy so I doubt low-level shear will be anything to write home about, but severe weather with a tornado or two in the Arklatex wouldn't surprise me.

 

 

That's true in a general sense, but it also depends on the circumstances. The low bias is a major factor when it depicts the synoptic pattern correctly with ample moisture, but severely limits daytime heating (due either to unrealistic cloudcover or convective parameterization) and thereby CAPE. To me, the classic signal for this issue (at least in the Plains) is when there's a huge warm sector with 60-65 F dew points, yet its forecast temperatures at 00z are also 60-65 F right up to the dryline.

 

In this case, though, the GFS simply doesn't indicate sufficient moisture for synoptic reasons -- namely, the antecedent frontal intrusion and downstream features not progressing enough. If dew points north of I-10 are really < 60 F on Saturday, its depiction of minimal instability will likely verify.

Sunday is the better day anyways, I don't know why you are so hung up on the Saturday point.

[brettjrob]

Sunday is the better day anyways, I don't know why you are so hung up on the Saturday point.

 

1. The exchange started out in response to andy's post

2. IMBY

[Stebo]

1. The exchange started out in response to andy's post

2. IMBY

1. ok

2. more than IMBY might be affected, widen your scope a bit

[Stebo]

Yeah, Sunday should have some potential now that the GFS is conceding on its former idea of lingering the trough in the SW all weekend. The ejection is fairly sloppy so I doubt low-level shear will be anything to write home about, but severe weather with a tornado or two in the Arklatex wouldn't surprise me.

GFS has 0-1km shear around 30kt from 21z Sunday to 00z Monday for the Arklatex, with the amount of instability projected (which is using the GFS cold bias) would be more than sufficient.

[OKpowdah]

I don't know about sig svr on Saturday, as there's still no sign on either the GFS or Euro of sufficient moisture return before sunset. Instability looks likely confined to deep south TX, where shear is sufficient (not great) but initiation seems questionable. The sole positive I'm seeing in the guidance is that the NAM, through H+84, is less aggressive in shunting moisture southward with the mid/late-week front. It doesn't have the big nor'easter at all like the GFS/Euro, which IMO will be a necessary condition for anything significant Saturday. I never like having to hang my hat on the NAM at this range, though.

 

 

Not sure what's preventing full-blown moisture return to be recognized in the models through. Got great trajectories off the Gulf leading into Saturday. Not to mention, I'm pretty sure model guidance busted on the moisture return today into southern OK. DPs in the low 50's ... granted, a huge N-S gradient across central OK.

 

But I think models might be underdoing BL moisture by Saturday.

 

Definitely way more interested in Saturday evening / night than Sunday for obvious IMBY reasons lol

[David Reimer]

Since I have to be in Colorado by Monday for a mandated vacation (girlfriend loves the place), I have to be driving up there by Sunday. As such, expect a major outbreak somewhere. That's my analysis of the situation thus far. 

[Stebo]

Not sure what's preventing full-blown moisture return to be recognized in the models through. Got great trajectories off the Gulf leading into Saturday. Not to mention, I'm pretty sure model guidance busted on the moisture return today into southern OK. DPs in the low 50's ... granted, a huge N-S gradient across central OK.

 

But I think models might be underdoing BL moisture by Saturday.

 

Definitely way more interested in Saturday evening / night than Sunday for obvious IMBY reasons lol

 

Agree with this post.

[patrick7032]

Well aparrently AT&T is having issues (IMAGINE THAT)...as I tried sending point soundings for 6 sites and a couple of dewpoint images...but it hasnt shown up in either of two email accounts That said...the data here at work shows the dryline passing through a San Angelo to Oklahoma City line between 9am and noon Sunday...and through a Little Rock to Shreveport line around midnight Sunday Night. I still believe the models are too fast...and likely will be even 24 hours out...as was the case with the last system. Unlike last system...point soundings largely agree with instability parmaters and hodographs as seen on Bufkit and web-based displays. If the soundings show up in my email...I'll post them. I did the soundings for KSJT...KSPS...KOKC...KDFW...KLIT...and Shreveport (didn't know the IDENT off the top of my head) Soundings generally showed 1200-1800+ CAPE and LIs -7...with TTs in the mid 50s. Nice hodos too.

[Stebo]

Well aparrently AT&T is having issues (IMAGINE THAT)...as I tried sending point soundings for 6 sites and a couple of dewpoint images...but it hasnt shown up in either of two email accounts That said...the data here at work shows the dryline passing through a San Angelo to Oklahoma City line between 9am and noon Sunday...and through a Little Rock to Shreveport line around midnight Sunday Night. I still believe the models are too fast...and likely will be even 24 hours out...as was the case with the last system. Unlike last system...point soundings largely agree with instability parmaters and hodographs as seen on Bufkit and web-based displays. If the soundings show up in my email...I'll post them. I did the soundings for KSJT...KSPS...KOKC...KDFW...KLIT...and Shreveport (didn't know the IDENT off the top of my head) Soundings generally showed 1200-1800+ CAPE and LIs -7...with TTs in the mid 50s. Nice hodos too.

 

If a dryline can get that far East into the Arklatex region, things could really go huge there during the evening hours on Sunday.

[andyhb]

00z GFS really wrapping up the vort max following a phase around 102 hrs.

 

This run has the wind profiles, but because it ejects so quickly, the warm sector begins to get pinched off with eastward progression.

[JoMo]

Since I have to be in Colorado by Monday for a mandated vacation (girlfriend loves the place), I have to be driving up there by Sunday. As such, expect a major outbreak somewhere. That's my analysis of the situation thus far. 

 

I also like Colorado, beautiful scenery. Ever chased there?

[David Reimer]

I also like Colorado, beautiful scenery. Ever chased there?

 

I've actually never been to Colorado!

[SluggerWx]

Just moved to Denver from Nashville last year, excited for the concept of VISIBILITY for once - might get to see my first tornado this spring.

Sent from my DROID RAZR using Tapatalk 2

[OKpowdah]

54/54 right now in Norman, with upper 50's dew points working into southern OK.

 

9.2C cap around 815mb in the 12z sounding is going a long way to prevent moisture from mixing out of the boundary layer. This is a perfect set up to maximize the efficiency of moisture return to the boundary layer.

 

Model guidance is definitely falling short on sfc dew points today

[ZackH]

I also like Colorado, beautiful scenery. Ever chased there?

 

I love me some Colorado chasing

[andyhb]

Models, especially the Euro continue to show significant overnight destabilization across TX, even into OK, Saturday night, through Sunday morning (Euro builds over 2000 J/kg in spots).

 

Could see some nocturnal action as the LLJ kicks into gear.

 

FWD is playing a bit of a dangerous game here playing the climo card here, IMO, with their latest AFD, with the type of instability that is being shown by the more reliable thermo forecaster out of the dynamical guidance compared to the GFS...

 

ALTHOUGH WIND SHEAR WILL BE HIGH...THE TIME OFDAY WHEN THE FROPA IS EXPECTED WILL LIKELY LIMIT THE SEVEREPOTENTIAL FOR THIS SYSTEM.

[thewxmann]

The noreaster Friday and Saturday is going to prevent this from being a more significant event.

[andyhb]

The noreaster Friday and Saturday is going to prevent this from being a more significant event.

 

I'm seeing far less effects than you might expect with a NE storm of this potential intensity on the warm sector at least further west, especially on the Euro...due to the track of the trough that creates the Nor'easter. This is not a Miller A/southern Miller B track that carves out the whole Gulf upon development.

[brettjrob]

The noreaster Friday and Saturday is going to prevent this from being a more significant event.

 

This. Seen it too many times to count, including one (non-)event last November. The 18z NAM paints an eerily similar picture to that one for Saturday evening, with wasted hodos to make grown men weep throughout the southern Plains.

 

 

^ my first time using memegenerator... I think I made it count.