4/22/10 FCST: TX/OK/KS/NE

[Andy Wehrle]

Just a n00b trying to take a stab at this:

If I were chasing and had to pick a target right now based off today's 12Z GFS, it looks to me like there is a sweet spot in SC KS/NC OK. West of there the 850 MB winds appear veered, and east of there that nice 500 MB jet streak rounding the base of the trough hasn't quite gotten there yet.

Maybe the GFS dewpoint guesstimate is out to lunch (surprise!) but I'd expect (want?) to see a little more moisure being pulled back toward the triple point and pooled against the synoptic warm front.

Thoughts?

 

[David Wolfson]

It's not yet in the forecast area, but I'd be interested in the area down toward Dalhart, TX. IMO the shear profiles are better down there for deep-layer rotation with enough dryline convergence. Capping may be a problem, but moisture, heating, and upper dynamics could pay enough dividends to break it, with some very nice storms the result. The upper level vorticity maxima seem to be taking a more southern path around the cutoff system, influenced by the subtropic jet south of the US border.

The challenges I see with the KS/NE area are rather linear vertical shear and the possibility of widespread cloud and precip across the area during the day. FWIW.

 

[Skip Talbot]

Definitely an interesting setup with a deep surface low, dryline, and ejecting trough. I'm a little worried about the timing of that ejecting trough. The upper level dynamics look like they might be in place early in the day with cap eroding away to nothing by noon. Storms might go up early, and with ongoing precip and convection forecasted down the dryline from NE to OK into TX, instability might be lacking. Still, the GFS is forecasting a narrow band of instability of around 1000 J/KG down the dryline with ample speed and directional shear for supercells. If the GFS is too fast, like it usually is, this might work in our advantage slowing the advance of that trough until the dryline is better established and the atmosphere has more time to destabilize. I think this setup could go either way at this point. I'm most interested in the dryline in north and western Kansas where the GFS is indicating modest, yet adequate instability. The surface winds back strongly here with SSW midlevel winds for a northerly storm motion with ample speed and directional shear for supercells.

 

[David Reimer]

I have the same thoughts as Skip regarding the setup. I've seen too many setups this year look good but convection then forms early in the day and causes the atmosphere to stabilize before the main event can get going. I'm very skeptical at this point for Texas and Oklahoma due to this. Instability is still there but with rain in the area all afternoon I'm not very confident in this setup. It looks good otherwise. However, It still is 100 hours out and not even in range of the NAM/WRF. It's purely guesswork at this point of the game.

I've posted a much more detailed analysis over on the website along with some graphics. http://texasstormchasers.com/2010/04/18/springs-acoming/

 

[Tim Supinie]

Yeah, I saw the early-morning convection earlier runs and was disappointed. I can't figure out why the GFS is generating precipitation that early, though. There's not much vertical velocity to speak of in the TX panhandle at 12Z 22 April. The 00Z 19 April GFS run has no temperature advection, basically no surface convergence, and the vort max placed over W CO. I guess the placement of the vort max is just close enough to the TX panhandle for it to support precip generation.

Now that we have the 00Z 19 April NAM run, we can see its opinion for 12Z 22 April. This run places the vort max over AZ and generates no precip in the TX panhandle, which seems more realistic to me, especially given the fast bias on the GFS.

Digging into this a bit deeper, the GFS and the NAM use quite different precipitation/convective parameterization schemes. The schemes the GFS uses are quite crude due to the computational expense of having to run them across the globe. The NAM's are a bit better because it's only run over North America, so they can afford to use higher-fidelity parameterization schemes. So the main point here is that my money is on the NAM currently. The reason for this is that morning convection, which the GFS does not handle very well, is the biggest wrench in the works I can see for Thursday. I guess we'll figure out tomorrow morning what the NAM really thinks for the afternoon hours Thursday.

But those are more small-scale details that the GFS/NAM are notoriously bad about 84-96 hours out, so they've still got plenty of time to change. One other thing that I think is of note that is a slightly larger-scale feature: both models agree on some less-than-spectacular mid-level lapse rates in the TX panhandle and western OK at 12Z 22 April, which may be a problem whether you have morning convection killing everything or not.

And I most likely won't be able to chase Thursday, so take that for what you wish. Anyway, my two cents.

 

[Andrew Ryan]

Well, the NAM is finally in range of Thursday now. Both the 12z GFS and NAM are firing convection in the morning but allow the atmosphere to destabilize in the afternoon. A good area of >2000 J/Kg is present in SW OK/NW TX.

The NAM and GFS are in fairly good agreement with the UL features, but this is most likely to change. Of course the GFS is still progressive with these features but is slowly down. The 0-6km shear is adequate but may cause storms to be more HP-ish in nature.

The NAM seems to be having trouble lifting the warm front not too far north of the Red River. This is most likely due to the ongoing precip in OK. The NAM usually has this problem, so I think the WF will likely make it into KS. But I think it will be beneficial to have the WF near the red river. This will allow for any storm that is able to latch on to increase the lack of low level helicity in the area.

The NAM is backing the sfc and 850 winds a little too much and reduces the 0-1km shear. The GFS paints a better picture for this with more S-SE sfc winds and S 850s. But both models have a meager LLJ (only around 35kts).

 

[Skip Talbot]

We're definitely seeing the GFS start to slow down, and the NAM is still slower than the GFS, hanging the trough over NM on Thursday evening vs the TX panhandle on the GFS. This is a good thing. With the trough arriving later, we can hold that forcing off until the atmosphere can fully destabilize. Both the GFS and WRF are showing more than 2000 J/Kg across the TX panhandle. My preliminary target is Amarillo and possibly points north, where the easterly surface flow across the Caprock should initiate storms and the midlevel flow send them up north towards the better directional shear along the warm front. Shear and instability look more than adequate for supercells.

 

[Brian Stertz]

NE Texas Panhandle looks very primed for legit monster supercells. 12z NAM has decent 0-3km shear and the nose of some higher theta air poking in from the south by evening. Right now I would probably select Pampa as the target by 6pm for a bad supercell or two. Things could get interesting with the southeast right movement too. Too far out of my chase range for Thursday unfortunately. Friday is another story...

 

[Chris C Sanner]

This looks like the middle day of an interesting 3 day chase setup across the plains. Thursday has the look of a C/E panhandles chase, with the GFS still being a bit fast on the evolution of surface features considering the EC has been winning the battle on trough progression all year thus far. NAM's placement seems a tad more realistic although the difference is rather minimal. NAM placing 3500 - 4000 SBCAPE across the TX Panhandle on Thursday with moderate wind shear, that's a winning combination if I've ever seen one.

Given most likely slower trough progression, I'm expecting Friday to be a chase day in doable terrain along the Highway 81 corridor or even further west as well, but forcing could overwhelm the target zone. Wednesday is more iffy and will be based on more localized triggers, but NAM/GFS both breaking out precip along the front in OK with slow storm motions progged.

More detailed forecast here: http://www.supercellhunting.com

EDIT: Thinking hasn't really changed as of Tuesday. SPC outlining the 15% hatched area gives some credence to my suspicions of this being a banner chase day.

 

[jamesmseitz]

How looking at everything I think my thinking of S Kansas is a bit to far north. With NAM showing a more southern track on this storm. The Texas Pan handle looks better every run but, Do not want to go so far south that I then head North to catch up. I am looking more and more at Woodward OK so I can still adjust as needed. Either way these days are not going to be the best of the season (at least I hope not but they look to be decent.... Leaving MN on Wednesday night with Robert Hurkes and meeting up with others.

 

[BrandonWhittington]

I think the models are doing a poor job on the Dryline position on Thursday. The amount of moisture that we have had the last few days, along with the weak 700mb winds, i dont see any reason that the dryline will progress any further than the central Panhandles, and that might be a little too far east. If i were to pick a target today, I would be sticking around Dumas area.

Every model runs are tending to more Cape and better instibility, throw the retreating warm front in there, Shear profiles are out the roof and with the amount of Helicity that is forcasting, I would not be suprised at all to see several tornadoes in the Northern Panhandles.

 

[Mike Johnston]

I think the models are doing a poor job on the Dryline position on Thursday. The amount of moisture that we have had the last few days, along with the weak 700mb winds, i dont see any reason that the dryline will progress any further than the central Panhandles, and that might be a little too far east. If i were to pick a target today, I would be sticking around Dumas area.

Every model runs are tending to more Cape and better instibility, throw the retreating warm front in there, Shear profiles are out the roof and with the amount of Helicity that is forcasting, I would not be suprised at all to see several tornadoes in the Northern Panhandles.

Actually, the overall setup at the surface looks more like a pre-frontal trough will be the dominant feature moreso than the dryline proper - and may even be a bit out in front of the dryline. Good convergence at the surface, and I think the mid- and upper-level feature look well-positioned and fairly well timed with the diurnal cycle on this day. Pretty nice 850/500 crossover, LCL's look very feasible, and I don't think initiation will be an issue at all.

All in all, I think playing it as reasonably far south as possible might pay off in this situation. Childress, TX might be a good place to start.

 

[Aaron Dooley]

I like Thursday...

00Z NAM/WRF run still has me very interested in the Childress area (40 miles radius or so) for Thursday.

The model/s aren't handling the precip well right now but based on what happened today I think the Childress area is a good spot.



Looking on the positive side in that area:



Surface dewpoint: 65-70

850 dewpoint: 15-18C

SB CAPE: 2500+

0-1 EHI: 1.50-1.75

0-3 EHI: 5.00-6.00

CIN: All but gone by 00Z

LI: -6 to -7

LCL: 750-250

0-1 SRH: 125-150

0-3 SRH: 250

Surface to 500MB Shear: 60 knots~

Storm motion: 15 knots out of the SW

 

[Mikey Gribble]

I like that area west of Childress too, but if I had to choose now I'd probably go with the area north of I40. The only thing I like more about that area is the possibility of slightly stronger winds at 850mb and 500mb and it's closer to home for me.

I just hope the NAM can verify. I think it's done a pretty good job so far until the hickup this morning. If the NAM stays on track and the other models fall in line tomorrow then I'll be a lot more confident with this setup. I don't like the level of uncertainty right now.
Overall I think it's probably the best tornado environment we've seen so far this year. If the NAM can verify, I think any discrete storms from Childress all the way back to the surface low could have decent tornado potential. I don't like seeing mediocre flow from 850mb through 700mb, but the directional shear makes up for that IMO. Pretty much everything across the board looks good (not great) for a solid tornado threat. I didn't spend much time looking at the 00Z, but I'll put a little more effort into my forecasting tomorrow morning. If I had to pick a target now I'd go with an initial target around the Guymon, Oklahoma area. I put up a brief forecast and map on my blog too http://loadedgunchasing.com/blog1/

 

[Eddie Natenberg]

BIG BIG DAY AHEAD OF US (IMO).

I think this could be the best day of the year so far. Nicely mixed BL strong pressure falls, backed surface winds. And decent 700 mb height falls along a strenthening LLJ. Forcing will be somewhat limited since it looks like a strong wave will move through the area in the morning and then propagate downstream through Oklahoma. Depending on what baroclinic surface boundaries exist tomorrow I would say sig tors are not out of the question. I fully expect SPC to go moderate svr risked with hatched tornado risk from KAMA -CDS -FDR tomorrow. =) Oh, I love spring patterns like this!