2015-12-12 EVENT: TX/OK/KS

[Taylor Wright]

I've been looking at this one a lot, and should be able to make it out this Saturday to chase, so I'll go ahead and start the discussion on this, albeit brief.

The uncertainty regarding this event still remains somewhat high despite only being two days out, due to the models differing on placement of surface features and regions of best instability. As the surface low moves eastward into Oklahoma, 20-30 kts of 0-1km shear should be present all the way from north-central TX into southern/southeastern KS.

The biggest fly in the ointment seems to be instability and initiation time, both not favorable due to warmer mid-level temps and poor lapse rates evident by both the GFS and NAM. Most of the recent NAM solutions have a massive MCS moving eastward of I-35 in eastern Oklahoma and Texas in the 21z time frame, not leaving much time for recovery for any discrete cells that may form on the dryline to the west. While the NAM is a bit more optimistic about instability (as usual), the GFS and NAM 4km agree with very marginal CAPE values of 500-750 J/kg. Relatively modest deep-layer shear values for this time of year (40-60 kts 0-6 km shear along the dryline) should keep updrafts from getting ripped apart, as has been an issue with some of the fall setups this year. The hope is that this, combined with very good low-level shear can make up for the lack of instability and we'll get some low-topped, tornado producing supercells. This setup has decent potential, but it seems that cloud cover and early-day convection may keep it from reaching that potential.

The best target area will likely be wherever the sun can poke through behind that MCS and where initiation will actually occur, as both of the NAMs have discrete cells only in southern KS by 00z, nothing in OK or TX. If I had to pick a target based off of what I've seen so far, it would likely be central Oklahoma down to the Wichita Falls area, where the best combination of low-level shear and instability should reside, although I may stay further north if adequate instability makes its way to the KS border along the northeast side of the low.

 

[Quincy Vagell]

One of the concerns I've had is a bit of a veer-back-veer setup in the soundings, which is creating some messy hodographs. At least the turning in the lowest 1-1.5km is good, but I'm just not overly thrilled by the setup.

 

[Drew Terril]

I've been watching this for a few days myself. I was fairly optimistic at first but not so much now with the hodographs looking messier and messier. The 18Z run of the NAM 4km seems to be much more optimistic than the previous run as far as CAPE is concerned though, and one can hope that the MCS leaves behind a nice little boundary.

My tentative target is Wichita Falls. If I work Saturday I won't be off till 1330 but that will leave me plenty of time to drive down that way. Certainly not ideal, but I'll take what I can get.

 

[Quincy Vagell]

The setup for Saturday has had a lot of question marks and red flags from the start, but now that the event is approaching, things are coming into better focus. The upper level pattern is split with a fairly complex setup forecast to develop. It looks like two pieces of energy will factor into the southern Plains severe threat. The first will be a strong daytime low-level jet across eastern Texas with vorticity maxima ejecting north-northeast toward the Ozarks Saturday afternoon. The second area of energy hangs back with a cold front and the more substantial height falls across the southern High Plains.

The greatest severe threat, although still somewhat limited, should develop from eastern Texas into perhaps southeastern Oklahoma/far southwestern Arkansas during the afternoon hours on Saturday. Aided by a 40-50+ knot low-level jet and modest instability, at least a few supercell thunderstorms could fire. Given the wind profiles, all severe hazards appear possible with perhaps a few tornadoes. The threat here shifts to damaging winds as storms merge and should tend to wind down after dark as daytime heating fades and the strongest forcing moves into the Ozarks and Middle Mississippi Valley.

The secondary severe threat looks to be from central to North Texas, into central and western Oklahoma. This could extend into Kansas, but with northward extent, instability will become increasingly limited. There are three issues with this area, with the first being a continued messy look to the wind profile. Model soundings have shown a veer-back profile in the mid-levels, producing some jagged, criss-crossing hodographs. Also, some warmer temperatures in the mid-levels should keep the atmosphere capped in most areas until early in the evening. Finally, the trough has slowed down a bit on the models, which also keeps the best forcing farther west until after dark. The timing is analogous to 11/16/15, but instability is significantly less impressive and shear is not as robust. Although a tornado cannot be ruled out, the threat is fairly low.

For this area, thunderstorms will try to develop around or shortly after sunset, but may have trouble organizing given the above-mentioned factors. Still, given cold advection aloft and moderate shear, a few briefly discrete/semi-discrete severe thunderstorms could develop. The most likely scenario is that thunderstorms form into a squall line and feature damaging winds as the main threat overnight.

 

[Ben Holcomb]

Pros:

• The setup is on a Saturday
• The setup is in Oklahoma

Cons:

• Look at 12Z RAOBS, everything is extremely dry. SHV, FWD, OUN, AMA, MAF, BRO, CRP, DRT are all extremely dry. LIX and LCH have some moisture, but it's very shallow.
• Not a lot of instability/CAPE
• The regular NAM shows capping during the day and until about 2 hours after dark
• the 4km NAM doesn't show so much capping, but some VBV in the hodographs
• I tore my ACL and Meniscus in my right knee and don't really feel like spending the day in the car
• Storm modes COULD go linear fast, although I'm not sure that's likely to happen given the amount of shear.

 

[James Gustina]

Not looking too good down on Red River in Harmon/Jackson/Tillman counties. The clouds have thinned out slightly but considering how thick the stratus deck is as of 17Z I'd venture a guess that instability might barely crack 500 j/kg ML. OUN sounding from this morning was also extraordinarily capped with a pretty dang impressive EML for this time of year (~10C). Moist layer is roughly 1 km deep but the shear profiles look like any supercells that do manage to get established are gonna have pretty wet, cold RFDs.

I decided to forego this one in favor of a night out with the girlfriend in OKC instead.