October 12-13th "Potential" Severe Outbreak

[Stebo]

I think it is a little early to be write of either day, especially considering the location of the system right now and that there is still several days until the potential event.

[brettjrob]

Slightly OT, but that 12 Nov 2005 analog that a few are mentioning spawned one of the better close-up home videos you'll ever see. Figured I'd post it for anyone who hasn't seen yet.

[andyhb]

Yeah, that thing is crazy...the immediate aftermath is pretty intense.

[patrick7032]

Arent you glad you didn't pay....lol.

Reed Timmer: Meteorologist and Extreme Storm Chaser

BIG PROBLEMS! Joel must have come by and severed some the audio lines on the Podcast. We've postponed the show 30 minutes until 9 pm Central/10 pm Eastern. Standby for updates. AAAAAAAAAAAAAA

[Superstorm93]

Considering how much surface theat-e difference exists between KC (300) and ICT (340) (using today's GFS run at a 72 hour forecast) there will definitely be widespread elevated convection that will shift east and northeast. In this scenario areas south of here will clear out ahead of the front faster/longer...and with the 250mb jet centered over Kansas (this run) versus west of OKC (last run)...the best entrance region and instability seems to be co-located in Oklahoma into southeastern Kansas...where the best chance for strong/long track tornadoes would be. Until the system comes ashore and gets at least 2/3rds of itself sampled by RAOB data...it's anybody's game.

Yeah, that's when the models should begin to converge on some sort of solution for this one.

Healthy sampling should begin tomorrow.

[patrick7032]

LBB mentions an October 21, 2010 analog. I checked the SPC events and didnt see it. Anyone have an idea what they were trying to refer to?

[brettjrob]

LBB mentions an October 21, 2010 analog. I checked the SPC events and didnt see it. Anyone have an idea what they were trying to refer to?

It wasn't a particularly noteworthy day overall. A couple tubes from a supercell in SE NM, though.

http://www.spc.noaa.gov/climo/reports/101021_rpts.html

TBH, I think Friday looks substantially better, at least on paper right now. Dew points should be 3-6 F higher and deep-layer shear significantly stronger.

[LocoAko]

LBB mentions an October 21, 2010 analog. I checked the SPC events and didnt see it. Anyone have an idea what they were trying to refer to?

Only seeing this. Hm.

[patrick7032]

Only seeing this. Hm.

Thanks Brett and Loco....I was looking in the storm events. Usually any severe dates are listed there. Guess they missed that day.

[Ian]

Slightly OT, but that 12 Nov 2005 analog that a few are mentioning spawned one of the better close-up home videos you'll ever see. Figured I'd post it for anyone who hasn't seen yet.

awesome

[Ian]

I'd like Boise City area in OK as a starting point for Fri, partly because there's not much else out in that area and that seems like a decent center point but maybe a bit east.

[Thundersnow12]

I like the Pecos Valley region for something isolated around 21z on Friday.

Say CNM-HOB-MAF-PEQ

[patrick7032]

I'd like Boise City area in OK as a starting point for Fri, partly because there's not much else out in that area and that seems like a decent center point but maybe a bit east.

Yeah...if it was in a better upper jet position...but okay position for the 500 jet max. Starting to think I'll hold for Saturday...but still plenty of time out there. I like your location from a setup point though. I was thinking of Dimmit, TX if I do go.

[brettjrob]

I'd like Boise City area in OK as a starting point for Fri, partly because there's not much else out in that area and that seems like a decent center point but maybe a bit east.

I'm not thinking too far off from that... perhaps hedging more toward DHT-AMA. The SREF SigTor is honing in there, and without a doubt the best hodos on NAM soundings are located in the NW TX PH.

There's no denying the ever-so-slight slowing trend on each run of the NAM, and if you extrapolate it through another couple days worth of runs, I'm nervous about the final impact on Friday. As it stands, there's only modest low-level cyclogenesis before dark with no consolidated sfc low. Those nice hodos really wait until right at 00z to pop up (at least in widespread fashion). Sunset will be ~0020 UTC with complete darkness by 0100.

By the end of the run, the NAM does no favors for Saturday, looking about as fast as the GFS and also even farther north with the vort max.

[andyhb]

00z GFS is ever so slightly southwest of the 18z run position at 96 hrs with the mid level low center at 90 hrs.

[brettjrob]

Friday or bust, folks. /troll

[Ian]

I'm not thinking too far off from that... perhaps hedging more toward DHT-AMA. The SREF SigTor is honing in there, and without a doubt the best hodos on NAM soundings are located in the NW TX PH.

There's no denying the ever-so-slight slowing trend on each run of the NAM, and if you extrapolate it through another couple days worth of runs, I'm nervous about the final impact on Friday. As it stands, there's only modest low-level cyclogenesis before dark with no consolidated sfc low. Those nice hodos really wait until right at 00z to pop up (at least in widespread fashion). Sunset will be ~0020 UTC with complete darkness by 0100.

By the end of the run, the NAM does no favors for Saturday, looking about as fast as the GFS and also even farther north with the vort max.

Yeah further south into the TX panhandle seems a bit better for now. I was thinking the same re the NAM on both counts.

[patrick7032]

I'm not thinking too far off from that... perhaps hedging more toward DHT-AMA. The SREF SigTor is honing in there, and without a doubt the best hodos on NAM soundings are located in the NW TX PH.

There's no denying the ever-so-slight slowing trend on each run of the NAM, and if you extrapolate it through another couple days worth of runs, I'm nervous about the final impact on Friday. As it stands, there's only modest low-level cyclogenesis before dark with no consolidated sfc low. Those nice hodos really wait until right at 00z to pop up (at least in widespread fashion). Sunset will be ~0020 UTC with complete darkness by 0100.

By the end of the run, the NAM does no favors for Saturday, looking about as fast as the GFS and also even farther north with the vort max.

I agree with you on all points. Right now I think I'll hold for the same reasons you mentioned and since I havent chased in those areas yet...but we'll see.

[patrick7032]

Friday or bust, folks. /troll

I absolutely wouldn't say Friday or bust by any stretch as Saturday has plenty of potential. True the 850-500 best winds lift north...but the shear is stll decent in eastern Kansas south...and with an incoming 250mb jet max...6km shear will increase. There will also likely be an outflow boundry intersecting the sfc front...better moisture pool...and better heating.

[PottercountyWXobserver]

I will be in the Tulsa area until Thursday, but I would consider staying in the region until saturday if you guys think It would be worth my time? I would be willing to chase up to 4hrs away but none further. I have to drive towards Dallas on my way home, so I may take a little detour

[brettjrob]

I absolutely wouldn't say Friday or bust by any stretch as Saturday has plenty of potential. True the 850-500 best winds lift north...but the shear is stll decent in eastern Kansas south...and with an incoming 250mb jet max...6km shear will increase. There will also likely be an outflow boundry intersecting the sfc front...better moisture pool...and better heating.

My issue is the direction of the H85 winds. The amount of veering on that map screams "bust" louder than just about anything else I can imagine. It may not verify, and indeed the 12z ECMWF was a lot "less bad" than that, but still.

I'm sure I'm getting obnoxious and sound like a broken record now, but experience says it's not just about shear and instability. This whole backed vs. veered LLJ issue is something that even NWS offices and SPC sometimes seem to overlook, but chasers can't ignore it because we've seen it so many times. You can have instability, excellent deep-layer shear, and huge 0-1 km SRH owing to extreme speed shear... seemingly all the ingredients... but the SW 850 winds still usually portend linear mode and advect in crappy air from behind the dryline that eats away at any supercells trying to develop. This isn't a problem in the Southeast, and it's a less-severe problem in the Midwest, but it's a show-stopper in the Plains usually. Maybe parts of MO or IA will be able to get away with it... we shall see.

[andyhb]

Maybe parts of MO or IA will be able to get away with it... we shall see.

This is where I've been looking for the GFS runs as of late.

[JoMo]

Friday or bust, folks. /troll

Linear mode squall line along the front.

[patrick7032]

Here are some LATE evening/night soundings for AMA and HOB.

[tornadotony]

Not gonna post as detailed an analysis as I wanted to, but a couple of points.

1) Chasers' nightmare. On Friday, the day where storm mode and likely storm structure are to be the most favorable, I think the bigger threat by far will be after dark. On Saturday, a more linear storm organization and wicked storm motions (50kt?), with perhaps some moisture issues (though I think, by and large, these are of somewhat lesser concern than I had originally thought). In short, the only real option for quality chasing will be late Friday afternoon in eastern NM, but with cyclogenesis not really likely to begin in earnest until around 00z, I don't know that the shear profiles for tornadoes will be there.

2) Overnight threat? We've already had a couple of these events this year, with the tragic EF3 tornado at Woodward during the midnight hour of 4/15 and a couple EF2 tornadoes in SE CO during the pre-dawn hours of 4/27. These events are uncommon but not unheard of on the plains. With cyclogenesis occurring during the overnight hours of Friday night into Saturday morning, you'll see a substantially intense wind field across the plains, which should suffice in keeping the PBL relatively mixed during the overnight hours and stemming much of a nocturnal inversion. This is shown pretty clearly in the recent GFS runs. As a related aside, the NAM (of which I don't take much stock past 48 h) shows significant overnight destabilization across western and central KS Friday night into Saturday morning. To destabilze locally overnight is rather rare. The destabilization is a product of the cyclogenesis, which leads to the retreat of the warm front northward across Kansas, as well as some weak CAA around 700 mb, which, combined, lead not only to a propagation of CAPE into KS but also an expansion and a slight elevation of maximum CAPE in the warm sector. There are likely other instances of this happening, but the only one I can think of didn't end particularly well (6 November 2005). Watch this in future model runs. If overnight destabilization continues to be modeled as we near the event, then I think the odds of an overnight severe weather outbreak will be substantially high.

3) Saturday is gonna be a tricky one. I think the odds are increasing that a more widespread severe weather episode is likely. Between moisture issues (I suspect the northward advancement of quality moisture is probably being overmodeled on the GFS and NAM) and sharper forcing, I am doubting just how substantial the tornado threat may be. However, I think that given adequate moisture and instability, along with very, very strong speed shear and good large-scale forcing, a widespread damaging wind event, likely with a few isolated tornadoes, is appearing more likely.

Bottom line: Supercell threat begins late Friday. Biggest tornado threat may be 03z-12z Friday night/Saturday morning. Most widespread severe wx threat is likely Saturday, from late morning through the afternoon and evening hours, until the storms reach the airmass farther east that will not likely recover due to the positioning of the ridge over the SE CONUS.

[baroclinic_instability]

Not really commenting on the severe threat at all since I haven't been watching closely enough, but hard to put any stock on NAM/SREF yet. They will all be at a huge vertical levels/resolution disadvantage compared to the ECMWF/RGEM/GEM/GFS. The speed at which they simulate the upper low seemingly "skipping" across the intermountain W complex terrain seems unrealistic. The ejection point seems even more unlikely (NW NE and S SD?) as vertical stretching would tend to keep the ejection farther S. Seen it time and time again with a northward and fast bias in NCEP guidance (NAM especially) under these setups...with all else being equal.

[andyhb]

Nov. 6/05 was Evansville I believe, for any who were wondering.

Excellent post Tony. And yeah I really overlooked the Friday overnight potential at first, but with a mixed boundary layer remaining and the LLJ accelerating to 40-50+ kts/sfc winds remaining backed as more substantial sfc cyclogenesis occurs, it could be a very real possibility.

[tornadotony]

My issue is the direction of the H85 winds. The amount of veering on that map screams "bust" louder than just about anything else I can imagine. It may not verify, and indeed the 12z ECMWF was a lot "less bad" than that, but still.

I'm sure I'm getting obnoxious and sound like a broken record now, but experience says it's not just about shear and instability. This whole backed vs. veered LLJ issue is something that even NWS offices and SPC sometimes seem to overlook, but chasers can't ignore it because we've seen it so many times. You can have instability, excellent deep-layer shear, and huge 0-1 km SRH owing to extreme speed shear... seemingly all the ingredients... but the SW 850 winds still usually portend linear mode and advect in crappy air from behind the dryline that eats away at any supercells trying to develop. This isn't a problem in the Southeast, and it's a less-severe problem in the Midwest, but it's a show-stopper in the Plains usually. Maybe parts of MO or IA will be able to get away with it... we shall see.

This is a good point that has recently been well-modeled for Saturday with this system. If you examine the last several GFS runs, you'll note how the instability axis lies in a zone where a substantial drop in 850-mb dewpoints is modeled, indicating exactly what you are referencing.

[patrick7032]

Not gonna post as detailed an analysis as I wanted to, but a couple of points.

1) Chasers' nightmare. On Friday, the day where storm mode and likely storm structure are to be the most favorable, I think the bigger threat by far will be after dark. On Saturday, a more linear storm organization and wicked storm motions (50kt?), with perhaps some moisture issues (though I think, by and large, these are of somewhat lesser concern than I had originally thought). In short, the only real option for quality chasing will be late Friday afternoon in eastern NM, but with cyclogenesis not really likely to begin in earnest until around 00z, I don't know that the shear profiles for tornadoes will be there.

2) Overnight threat? We've already had a couple of these events this year, with the tragic EF3 tornado at Woodward during the midnight hour of 4/15 and a couple EF2 tornadoes in SE CO during the pre-dawn hours of 4/27. These events are uncommon but not unheard of on the plains. With cyclogenesis occurring during the overnight hours of Friday night into Saturday morning, you'll see a substantially intense wind field across the plains, which should suffice in keeping the PBL relatively mixed during the overnight hours and stemming much of a nocturnal inversion. This is shown pretty clearly in the recent GFS runs. As a related aside, the NAM (of which I don't take much stock past 48 h) shows significant overnight destabilization across western and central KS Friday night into Saturday morning. To destabilze locally overnight is rather rare. The destabilization is a product of the cyclogenesis, which leads to the retreat of the warm front northward across Kansas, as well as some weak CAA around 700 mb, which, combined, lead not only to a propagation of CAPE into KS but also an expansion and a slight elevation of maximum CAPE in the warm sector. There are likely other instances of this happening, but the only one I can think of didn't end particularly well (6 November 2005). Watch this in future model runs. If overnight destabilization continues to be modeled as we near the event, then I think the odds of an overnight severe weather outbreak will be substantially high.

3) Saturday is gonna be a tricky one. I think the odds are increasing that a more widespread severe weather episode is likely. Between moisture issues (I suspect the northward advancement of quality moisture is probably being overmodeled on the GFS and NAM) and sharper forcing, I am doubting just how substantial the tornado threat may be. However, I think that given adequate moisture and instability, along with very, very strong speed shear and good large-scale forcing, a widespread damaging wind event, likely with a few isolated tornadoes, is appearing more likely.

Bottom line: Supercell threat begins late Friday. Biggest tornado threat may be 03z-12z Friday night/Saturday morning. Most widespread severe wx threat is likely Saturday, from late morning through the afternoon and evening hours, until the storms reach the airmass farther east that will not likely recover due to the positioning of the ridge over the SE CONUS.

Nice discussion Tony. I agree on all your points. I wouldnt expect a widespread tornado threat on Saturday...but like you said there will be some...especially if any MCV's (likely to develop) interact with any boundaries.

[Hoosier]

Nov. 6/05 was Evansville I believe, for any who were wondering.

Yes