2/10/09 FCST: TX/OK/AR/MO/KS

[Chris Wilburn]

Just glancing at the 00z run of the NAM things still look very interesting for tomorrow. 998mb low in SE CO with a very sharp dryline from about I-40 in OK and points to the south (the further south the sharper). Dewpoints right near 60 and temps. right near 70 appear likely along the red river just west of I-35. SBCAPE around 1,500 possible in this are along with 150-200 0-1 SRH and 200-250 0-3 SRH. Surface winds will be slightly backed and the 850mb winds should be southerly or maybe slightly "veered" with 500mb winds SSW. Plenty of moisture, instability and shear to work with. Storms should be moving fairly quick around 45 kts from one sounding I did on earl's page. Very nice setup for the first 1/3 of February. If I were to chase I would head towards Ardmore and adjust from there. It would really be nice to see things back up ever 75-100 miles or so. Anyway, SW OK, SC OK into NW TX look like a good bet tomorrow. One negative I see is the somewhat lack of directional shear with the 500mb winds more SSW than SW and the surface winds only slightly backed but that may be getting a bit picky I guess. Central OK looks good as well although there will have less moisture and instability to work with. Will see what the GFS looks like in comparison here in a little bit.

 

[Matt Chatelain]

Mama mia, supercells line up and march across central and eastern oklahoma according to the 4km wrf. Mighe be a wishcast for better chasing terrain but have been thinking that the best target might be further north (Pauls Valley to OKC points east) than recent thinking, right on the northern edge of the instability axis. Winds seem to back more on the wrf further north. Just have to see where the moisture return is located in the morning.

Somewhat reminds me of Febuary 28, 2007, where supercells fired right along the northern edge of the moisture/instability axis, where shear and instabilty come together.

 

[Jason Young]

I think south central Oklahoma look's good at this time . If model run's hold up .Have to work till noon , but plan on targeting Ardmore . BUT have been thinking of Sherman Tx. if I can get off earlier .

 

[Bill Schintler]

Chase Target for Tuesday, February 10

Chase target: 15 miles southwest of Denton, TX.

Timing and storm mode:
Storms will initiate first in central and southeastern OK and then build to the south towards the target area by 3:30 PM CST. Storm mode in OK will tend to be multicell with embedded supercells, while isolated supercells will be more likely further south in TX before an evolution to a squall line in both OK and TX with embedded supercells and bowing segments by 6 PM.

Synopsis:
The second of two ULVL systems will traverse through SWRLY ULVL flow Tuesday. Currently, the ULVL trough and associated SHRTWV are moving across SRN CA and AZ; with strong forcing and an area of convection over AZ tied to this assent. MDLs agree to take this feature through NM and then into WRN TX by 00Z Wed, while closing off and deepening. There is still considerable disagreement on the track of the SFC low, with the WRF favoring a much more NLY solution then the GFS. SWRLY SFC flow will persist for the next several hours, and later the DL pushes back W overnight as winds back and low-pressure takes shape over WRN TX. Area 00Z soundings (FWD, OUN, and LMN) indicated meager LLVL moisture; with the deeper moisture remaining well to the S and E (SHV). Recent SFC observations (05Z) indicate mid-50’s dewpoints N to the Red River, and this is consistent with MDL initiation. At the SFC, low pressure will track through the NRN TX panhandle between 18Z and 00Z Wednesday. The LLJ will increase to 60 kts by late afternoon while a couple of WAA showers or storms may develop in the morning and early afternoon, especially N of the Red River in SERN OK. The main show, however, will be discrete convection along an advancing DL after 21Z.

Discussion:
The preferred location will be along the SRN periphery of a convective complex on SRN OK. The best area for discrete storms should be along and S of the Red River along the DL, with more widespread convection and associated cloud cover further N. Later, storms will evolve into a squall line with STG ULV support, and push quickly EWD with damaging winds the primary threat. Unlike the case today, ample instability is advertised with MLCAPE’s increasing to 1500J/kg by 21Z along with weakening CIN. An area of CI associated with the ULVL system will inhibit insolation E of I-35 in the morning hours, however this feature will push E by early afternoon. SFC dewpoints of 60F should surge north to the Red river and E of I-35 by 00Z, while H85 PROGs show 10-12C dewpoints in the same areas. An SC deck will thicken between 17Z and 20Z along and E of I-35; and this will precede deep convection. An interesting note: a look at the 4 km WRF-NMM initiates convection along I-35 just S of OKC in OK between 21Z and 22Z, and then builds it to the S to just west of DFW through 23Z. Deep-layer shear will increase to 70kts with the approach of the S/WV, while (SFC-3km) hodographs increase as a 40kt LLJ veers to the SW over SLY SFC flow.

Feel free to PM me for nowcasting.
- Bill
11:48 PM CST, 02/09/09

 

[Brandon Sullivan]

I will be stuck at home, but am nowcasting for a friend.

Looking through 00z Suite and at 4KM WRF I am saying McAlester OK for a prelim target. Looks to be the best co location of thermodynamics/kinematics.... Good luck everyone.

 

[John MacKay]

Signs seem to point to supercells along and east of the I-35 corridor as shown on the 4km WRF, then evolving into a line around to an hour past sunset as Bill Schintler pointed out in his forecast. Based on what the 4km WRF shows, I would agree with the hatched 15% tornado probability placement, as supercells transitioning into a line with some embedded supercells in a properly sheared environment would suggest, later transitioning into a damaging wind event in AR. The NAM has also trended toward bringing the northern extent of the activity to much of SE KS and moving into NC MO as the low moves into those regions, which has also been captured in slight risk area of the latest SPC outlook.

If I were out there, I would agree with Brandon's target, but target more of a line on US 69 in between Atoka and McAlester to give options in every direction.

 

[Marc Austin]

The WRF simulated reflectivity is definitely picking up discrete cells along I-35. You guys who live out that way are just plain lucky! Take a look! Good luck.

23Z:

24Z:

25Z:

Looks like an interesting day. If it's a good day, maybe some of you can bring some footage out to the convention this weekend! Good luck to all chasing tomorrow.

 

[Terry Tyler]

Ive noticed on some of earl bakers NAM models a couple areas of 120+ 0-3km cape in NE AR. The conditions dont look as impressive as OK/TX but look alright to me. A number of other conditions are also culminating around the area around the same time the 'main' weather initiation goes on in OK/TX.

Does anyone have an opinion on this? Looks to me like NE AR might not be a terrible place to be.

http://wxcaster4.com/nam/CONUS_ETA_0-3KM_CAPE_24HR.gif
http://wxcaster4.com/nam/CONUS_ETA_0-1KM_SRH_24HR.gif

Maybe im missing something. I never went to school on this...

 

[Matt Gingery]

Looks like the models are still in disagreement as to where this surface feature will track. At this point, I don't even care, with SPC saying that a PDS will likely be needed today. Major tornado threat out ahead of the dryline from 21z on, and I am going to be sitting at ground zero. I don't think anyone should miss this event. This one is worth buying a plane ticket for. Just waking up to pack up and head out, and I log on to notice the large MDT risk area posted, and just get gitty. I will be leaving SGF even earlier now, and I am headed to OKC. We will be posting footage and video as it comes in to those who are unable to chase the event. I wish the best of luck to everyone, and make sure to play it cool and stay safe. SPC is calling for some significant ropes across the I-35 corridor, and as the LLJ strengthens and this dryline mixes east, its on for sure, just be safe. . .

 

[Brendon Lindsey]

Is the dryline any further East of where it has been forecasted because I was looking at dewpoints, and we go from 55-60 to 30 just 75 miles west of I-35 in NC TX. Is it going to be pretty stationary? If I recall most my May Chase Days the DL was a good ways off in the morning.

I will be in Ardmore around 12:30. Keep eyes open for a White Gaewoo (Daewoo).

 

[Michael O'Keeffe]

Is the dryline any further East of where it has been forecasted because I was looking at dewpoints, and we go from 55-60 to 30 just 75 miles west of I-35 in NC TX. Is it going to be pretty stationary? If I recall most my May Chase Days the DL was a good ways off in the morning.

I will be in Ardmore around 12:30. Keep eyes open for a White Gaewoo (Daewoo).

Brendon, the reason that is happening is because the warm front is just south of that area so the winds are out of the west. If you look at the surface obs it is only 44F in Wichita Falls, but it is 55F in Gainesville. So as the warm front lifts north today those winds will whip to the S and SE and begin drawing up that deep moisture.

Here is the water vapor imagery from 6am today and you can see the dry air back in W TX extending into the Panhandle and that is your dryline.
http://www.spc.noaa.gov/exper/mesoanalysis/frames.php?sector=5

 

[Jim Bishop]

Well this is the best setup I can remember in February for the Southern Plains. It's one of those rare winter tornado outbreaks you get once every few years (which is misleading because this is a classic April setup in early February!).

I expect discrete supercells to fire along the dryline late this afternoon all over Central OK down to North Central Texas and race northeast around 40-45mph.

Shear will be great for discrete supercells producing tornadoes over all of north/northeast TX and Central to Eastern Oklahoma. But the best region for long track, violent tornadoes will be Central to East Central Oklahoma down to near the Red River stretching eastward into Western Arkansas after dark. This will be the result of enhanced 0-1km helicity values as surface winds back in response to a deepening surface low over the TX/OK panhandles late in the afternoon/ealy evening.

These won't be easy storms to chase due to a fast storm motion, an increasingly bad road network as you head northeast, and not good chasing terrain. But if you are able to chase today you should because any discrete supercell that forms will likely produce a tornado at some point during its life. And there will be a couple storms that produce long track, violent tornadoes.

 

[Eric Sipes]

Bad chase terrain or not, I'm goin'!!! I'll be tageting from Pauls Valley to Ardmore. Basically anywhere along I-35 with good East options. Storms will fire along a stationary dryline along and just west of I-35 near 21-22Z. They will quickly organize and move ENE at 40knts. All I can do know is pray for some good roads. Most of the issues stated earlier have now all but disappeared. The 850 winds are still slightly veered but, I don't think that will do anything but place a weak cap and keep the storms isolated until after dark. Almost all other dynamics are in place for a very good chase opportunity in February.

Stay safe and good luck to all that chase,
-Eric

 

[Chris C Sanner]

Just a quick observation from the 12z runs, looks like they all have the dryline backed way up from last nights run, almost a Hobart to Clinton to Enid line now according to the RUC (farthest west model this AM). Cape is also progged at 1500+ in C Oklahoma this afternoon with very backed LL wind fields in 60-ish TDs. Uh-oh!

Update: Looks like the storms form between 21z to 0z to the west of 35 and then race NEwd into the very favorable shear. Given Oklahoma's track record, this will either squall out quickly or it'll be a massive cap bust since 15% tornado days have had a knack for busting in Oklahoma the last several years

Like I have been saying though, one of these days one will verify..

 

[Jordan Hartley]

This whole time ive been feeling left out since I have to work today(first day at new job.) I wake up, jump on SPC and . Looks like a classic tripple point setup later today along and north of the OK/KS border. If things pan out just right enough moisture should make it all the way up here to make things interesting later this afternoon/evening. Obviously the "big" show will be south into OK/TX, but this is christmas all over again for me Going to make a few calls and get things ready for this afternoon just in case. Good luck to everyone headed out today. Be safe and be blessed.