2012-02-03 FCST: KS, OK, TX

[samuel stone]

An interesting Quasi cut-off upper low ejects out Across Kansas and northern Oklahoma on friday. i've been a little hesitant to post on this because its febuary and its a little far out. However, the NAM has been fairly consistent with this system ever since it picked up. With generally unidirectional flow and unimpressive instability im not terribly excited about Supercell tornadoes anywhere with this setup with the possible exception of the red river south into n. texas.

Now, im not going to get into too much detail since its still way early. But. What i'm seein is a cold core set up in the making across southern or central Kansas. exact location has been shifting on a run to run basis, per the NAM. At any rate.. essentially we've got a neg 20 deg C - neg 25 deg C 500 mb low overlaying middle 50 deg F dp's and 60 deg F Temps with a nice mid level dry punch crossing over it allowing descent lapse rates to take shape along the boundary. All of this no further north than salina and no further south than Enid depending on model runs. Like i said not gonna get into many details with this yet but its worth watching and maybe worht a post or two on here. hey for FEB 3 ill take it. ESP. since this is my best day of the week to chase and its very local.

Thoughts?

 

[Jeff Snyder]

Sam beat me to the punch. I'll base this post primarily off of the 00z NAM since I don't have time to look at much else.

This setup looks a bit like one of those nice "cut-off, cold-core 500 mb low" setups and a bit like a "normal" synoptic setup. Typically, the surface low is more occluded beneath the 500 mb low in the "cold-core" events, with a Pacific front or dryline having pushed well southeast of the sfc low. In this case, though, the surface pattern looks a bit more "normal", with a cold front trailing southward from the surface low in south-central Kansas, and a warm front arcing northeastward and eastward. Temperatures in the middle and upper troposphere are progged to be sufficiently cold (maybe -25 C at 500 mb above the surface low) to lead to some decent CAPE considering the time of year (very early February) and the forecast surface thermodynamics (e.g. low-mid 60s temps and mid-upper 50s dewpoints). Associated with the cold air aloft (actually, the cold-air advection in the middle troposphere), the wind profiles do show a veer-back-veer tendency in many areas near the sfc low during the afternoon. However, the low-level shear could be worse, and there looks like there'll be a very nice warm front along which storms may get "interesting". The nearly-meridional flow near 500 mb is likely to give a storm motion with a strongly-meridional component, which also tends to be a nearly perpendicular to the warm front. This means that storms may interact w/ the warm front for a relatively brief time (perhaps long enough to be "interesting") before crossing into the more stable near-surface air N of the warm front.

The 00z NAM (again, that's my primary tool tonight owing to time constraints) does show a nice dry slot aloft working through central KS during the day, which should clear out cloud-cover aloft and allow for some insolation and destabilization by afternoon. All in all, it looks like a day that I'll have to keep an eye on (errr -- on which I'll keep an eye). I'm primarily focused just N of ICT right now.

EDIT: OK, glanced at the 00z GFS, which is farther southwest with the low aloft and which has a weaker sfc low. Overall, the 00z GFS looks less favorable for a chase event compared to the 00z NAM, IMO. There may a wacky situation along what looks like a stationary front or inverted trough WNW of the sfc low in western KS if the GFS is right, but "meh".

 

[samuel stone]

In regards to Kansas..

Well the 12z NAM has sped things up a good bit this morning and my cold core scenario is looking less likely with surface features looking more and more traditional in nature (not much of an occlusion at the surface) and 500 mb temps have warmed a little or at least not positioned as favorably over the surface moisture. In regards to more traditional SUPS in the warm sector, (wich has been moved to east of I-35 now in Kansas) im not digging amount of veering we have betwenn 850 and 500. which is next to zero. and im also starting to see some dry air entrainment at 850 from the southwest nosing up into SE'ern Kansas, which is one of my pet peaves. also the 12z NAM has veered the surface winds more in the warm sector. drive yourself crazy storm speeds and a wind profile im liking less and less, combined with surface instability which i'd only really like if they were associated with a moisture wrap/cold core scenario. and i'm just not nearly as excited as i was.

I havent checked if the GFS has spit out its 12z run yet but at last look the 06z run was considerably slower with this system. generally the surface winds were a little weaker but were backing more than the latest NAM run per the 06z GFS. I didnt look at that 06z run much figuring i'd just wait for the 12z to come out so I may post another update after I have a chance to analyze the new GFS run in a little while... definently some differential between the two models right now it appears so this things still up in the air id say.


Still a tad early to throw in the towell so ill continue to monitor the model runs and cross my fingers for things to trend better.

its FEB3 were talking about so.... well take that however you want to i guess. I'm not gonna loose my temper over things in Febuary. I'm really still in winter mode as it seams everyone else is.

EDIT: severe weather or not.. im just pumped about getting some RAIN here in the southern/central plains. its a godsend. I hope we can get into a wet pattern here into the early spring, the water bodies need it.

 

[Andy Wade]

Anyone know what happened to the 12z NAM? I tried TwisterData and OU's HOOT site, and only a few frames of the run are available on either page. 18z's out now anyway, just curious.

18z NAM continues to pick up on a small pocket of instability pretty much right around the middle of the surface low, beginning near Wichita and moving slightly NE during the afternoon. As everyone probably saw, SPC went Day 3 slight risk for the Dallas metro and not much else, with "see text" north into KS. I admit as a second-year undergrad I have no experience with cold-core setups, though after Intro I the meteorology makes sense to me. I know the target area for such a scenario is always pretty small area-wise, but some of the NAM runs are just ridiculous with the tiny, tiny bullseye of 1000+ CAPE and crazy LIs. The one reason I'm still holding onto the cold-core thing is that I absolutely do not want to go to SE OK--I'd rather see one EF0 on the ground for thirty seconds in S KS than a wedge ripping through the trees around Broken Bow. The thing is, right now neither of those seems very likely! Instability in the conventional warm-sector area down through SE OK to Dallas is looking slim. Forecast hodos everywhere have gone to crap, per NAM. Also, GFS has yet to really zero in on the favorable area in KS. On top of it all, both NAM and GFS have had a couple outlier runs where the surface low was almost to Missouri by late afternoon--not in my range for sure, and pretty far from the upper low. I know cold-core tornadoes don't require very impressive traditional parameters, but I still say equal chances that I chase or sleep in, watch the rain, and do calc homework.

On a side note, this morning, the SREF painted a nice picture for N OK, putting the surface low out closer to the Panhandle. Just saying.

 

[samuel stone]

Andy you hit on this a little bit and i'll reinforce. With the models in disagreement and with run to run consistency in disagreement. its hard for me to put much faith in anything right now. However the median scenario still seems to be a weak pocket of instability in south central kansas with less than desireable surface wind fields and a veer back veer profile with height. yet more often than not the Nam has still shown some overlap between the 500 mb cold air (-20 C and below) and this pocket of instability, Also the NAM has trended upward with the surface temps, probably owing to the well defined mid level dry punch which has been consistent on a run to run basis allowing nice insolation to spread across the are of interest.. which helps our cold core chances. but again theres not really a moisture wrap of any kind. which is rather non-traditional when in comes to cold core scenarios.

GFS, sref, NAM, they dont agree at all and like andy said theres been outlier runs. so wait and see ig. I wouldnt mind the SREF verrifying.

 

[samuel stone]

no time to get into detail right now but based on the latest NAM the best bet for rotating storms has shifted south into western/sw'ern oklahoma near where the triple point sets up. still got a small pocket of instability in sw oklahoma but its quite anemic on the 12z nam, and we still have very little turning from 850-500mb. appears right now as though we could have some major problems with ongoing convection a the start of the period.if i get a chance later i may post with more details. i most likely wont be chasing unless things take shape into northern oklahoma. i dont enough time or money to chance a very marginal chase thats over 350 miles away. as sad as that sounds.

 

[Andy Wade]

06z NAM is intriguing; turns the SE OK-NE TX setup to nothing and focuses the action in S to SW OK! CAPE > 1000 there with at least a shade of helicity and decent shear. I may or may not chase, but if I do, based on this my starting target would probably be close to Lawton. There are options west, east, and south from there, and most importantly, places to get wifi and keep tabs on this apparently unpredictable scenario. Given what we've seen so far, I fully expect to wake up tomorrow to something entirely new on the 12z models...and expect them to be wrong too. Also, it might be worth noting that as of right now, MCS(s) ongoing in W OK are mostly remaining some distance N of the Red River. It needs to stay that way through the morning.