4/25/09 FCST: NE/KS/OK/TX

[Chris C Sanner]

Yeah, at this point I'm not trusting the NAM for this weekend at all...I know models are crazy sometimes, but the NAM is reaching a new level on the scale as of right now. It has been consistent, but it brings a very strong cold front down into C/SW Oklahoma Saturday and then a day later there are no traces it ever existed as it completely wipes it out....I'm not sure that's very realistic.

I'm going to side more with the GFS for this weekend, not because it fits a better wishcast, but just because it has been a lot more consistent and seems a lot more realistic to the whole setup. With that said....

The GFS paints a very good picture for Saturday for either the Triple Point or for a more isolated storm coming off the dryline. With how the GFS tends to underestimate CAPE by quite a bit sometimes, I wouldn't be surprised to see nearly 3500-4000 CAPE in NW Oklahoma tomorrow with 3000 down the dryline. The hodos look very favorable per the GFS, and anything isolated (and especially something that turns right) will probably be a rather nice storm.

There are multiple targets one could pick, and I'm sure everyone will have their preferences based upon Warm Front vs. Dryline Chasing. I think we plan to split the difference, at least initially to keep an eye on the dryline just in case something more isolated pops...but the triple point looks to be a winner tomorrow, so it's not unwise to just sit there and wait. Good luck to everyone chasing, hopefully we all can come home with something good

 

[Mike Smith]

it brings a very strong cold front down into C/SW Oklahoma Saturday and then a day later there are no traces it ever existed as it completely wipes it out....I'm not sure that's very realistic.

It appears to me that the front moves rapidly north as a warm front across Kansas into southern Nebraska by 18Z Sunday. However, this is inconsistent with the showers and thunderstorms also predicted by the NAM across central Kansas on Sunday. I have a discussion regarding what seems to be an internal inconsistency in the model in the Sunday thread at:

http://stormtrack.org/forum/showthread.php?t=20372

Mike

 

[Chris C Sanner]

It appears to me that the front moves rapidly north as a warm front across Kansas into southern Nebraska by 18Z Sunday. However, this is inconsistent with the showers and thunderstorms also predicted by the NAM across central Kansas on Sunday. I have a discussion regarding what seems to be an internal inconsistency in the model in the Sunday thread at:

http://stormtrack.org/forum/showthread.php?t=20372

Mike

Very good point Mike...I'm just skeptical such a strong cold front would move so far north in such a short time period...not unheard of, but I just don't feel it's rooted in complete reality. I think the NAM is right about a cold front stalling and then lifting north, but I don't see it getting that far south and then that far north in such a short time period. So as far as impacts for Saturday go, I'd say the GFS seems a bit more realistic in terms of movement of the front.

 

[Adam Penney]

After looking at the 12z runs, I'm happy with a southwestern Oklahoma target for tomorrow, and won't be moving far to reposition for Sunday. Parameters look good enough to me tomorrow to warrant a drive, especially just to get into position for Sunday, if nothing else. SigTor has a bullseye on the state line with the TX panhandle, with fcst ML CAPE in the >3000 J/kg range. Scott and I will likely head down to this area tonight after work to get into position. It's worth it for a 'day before the day' situation, IMO.

I agree Mike. I have tickets to the royals game tonight(Zack Greinke a.k.a Filthy McNasty is pitching tonight)so unfortunately I can't hit the road until tomorrow morning. I'm going to plan for enough time for a SW OK target(if the NAM verifies), so I will be departing around 6-7 a.m.

I will also be staying out for Sunday's chase as well, with a return trip home on Monday unless something else crops up for that day. I'm more than likely going to be staying in AMA on Saturday night.

The 12Z NAM and GFS still seem to be sticking to their guns on their front placement difference. I'm still hoping for the GFS to verify. It seems on the upper level winds have increased a smidge on the 12Z runs which we could use.

I am encouraged for the next two days. Looking very much foward to getting out.

 

[Matt Gingery]

GFS actually places the best probabilities along the Kansas/Oklahoma line south of Dodge. NAM is playing an area to the west of Elk City with the the best 0-1/0-3km EHI as well as the best CAPE. We will be heading out early Saturday and heading to Elk City as a noon time staging point. . .

 

[Alex Lamers]

To be fair to the NAM, both it and the GFS depict chaseable events. Both also erode the cap sufficiently through heating and forcing to erode the cap around 5 or 6 PM. The NAM develops stuff further south and a bit further west, in the Wheeler, McLean and Shamrock areas in the Eastern TX Panhandle. The GFS instead lights up a portion of the dryline from Coldwater/Ashland, KS south to around Erick and Sayre, OK.

I'll post some more complete thoughts once the GFS and NAM completely come in from the 12z runs, but either way it looks like a decent chasing day if you head somewhere in WC Oklahoma.

AJL

 

[Gabe Garfield]

Let's see if I can post here...

VOILA! Great.

Anyway, Saturday looks pretty darn good, IMO. Really, the only thing I'm concerned about is storm mode and whether or not the LLJ is really able to crank by 00z. I have the feeling both will be answered in a positive manner, and tomorrow will be the beginning of a rather nice stretch of severe weather for the Plains. It's too early to nail a target, but I think the triple point sounds reasonable, unless sufficient low-level shear is able to manifest along the dryline.

Otherwise, I think this could be the beginning of what could be a week (or more) of prime chase weather. Sunday will probably be good as well, with low-level shear more than adequate for tornadoes, given the weak to moderate instability that is progged in all models. After this, next week could go gangbusters -- in the Wed/Thurs time-frame -- but that's for another thread.

 

[Brett Roberts]

GFS actually places the best probabilities along the Kansas/Oklahoma line south of Dodge. NAM is playing an area to the west of Elk City with the the best 0-1/0-3km EHI as well as the best CAPE.

It's aggravating that the models are not even beginning to converge on a solution as we enter the 24-36 hr. timeframe. The GFS looks extremely favorable for tornadic supercells over NW/WC OK and far SC/SW KS, with the cold front becoming stationary by early afternoon and a sub-1000 mb surface low forming along it W of AMA - this strengthens and backs surface winds in the warm sector, yielding better-looking hodographs than on the NAM. While SW OK looks pretty good on the NAM, low-level winds could be a limiting factor for widespread/significant tornadoes should it verify.

 

[Mikey Gribble]

Just when it looked like all hope was gone, the GFS turns around and comes back through for us.

Nice triple point along the OK-KS border with CAPE AOA 3000J/kg all the way from east of the triple point down the dryline. It has convection breaking out at the triple point/front just east of it and more convection further south. A rapidly deepening surface low backs winds across the warm sector to SE and puts them straight out of the east along the boundary. Even 850 winds are out of the south-southeast just ahead of the triple point. Although 850mb winds are only progged to be in the 30kt range along the border area (stronger down south) that is plenty good enough. Directional shear in the 0-6km layer is great. Deep layer shear could be better (it's around 45kts), but moderate to high instability will more than make up for that.

It presents such and easy chase with an easy target selection. Slow moving supercells (may be a little wet) with a few tornadoes would be great. I'm a directional shear junkie so even though the hodograph for Alval and Medicine Lodge aren't long, I really like the curvature.

Now I just have to spend the rest of my day pulling my hair out in an effort to figure out which mode is telling the truth. One target is a couple hours away and the other one is about six hours away.

 

[Glenn Dixon]

To be fair to the NAM, both it and the GFS depict chaseable events. Both also erode the cap sufficiently through heating and forcing to erode the cap around 5 or 6 PM. The NAM develops stuff further south and a bit further west, in the Wheeler, McLean and Shamrock areas in the Eastern TX Panhandle. The GFS instead lights up a portion of the dryline from Coldwater/Ashland, KS south to around Erick and Sayre, OK.

It's 38 miles from Shamrock to Sayre. I'd say those models were in a fair amount of agreement, unless we're now expecting them to resolve to the square meter....

 

[Kiel Ortega]

It'll be a late show given the forecast cap, so for those worrying about the details, you should have plenty of time to get to the target area (wherever that lands). Having looked at the forecast soundings, I think the models are in pretty good agreement with the environment, especially the forecast kinematics; just maybe not exactly where (which, as I mentioned, ain't that big of a deal). Unfortunately for folks living in which ever areas in which stuff happens, they'll be in store for a long night as the forecast hodographs get loopy and long in the low levels (0-1km SRH does a 1.5-4x increase--depending on which model--from 00-06Z!). All in all, looking more and more like a head-for-the-triple point chase.

 

[Matt Gingery]

We are heading out from SGF around 8 a.m. Destination OKC around 1 pm to figure out what model run to go with. Personally I feel that the NAM depicts the best overall set up. I think having both models in agreement that the CAP will go around 5 draws both models together. Should be able to get descent action anywhere along the dryline as far south as Wichita Falls. I like the EHI data out of the Lawton area from 5-7 pm. We may hang in OKC and catch the stuff up north of Elk City if the CAP goes there early and then draw back to Lawton, Ok. Should be a 25+ event tomorrow, and 50+ for Sunday. Model consensus is that there will be a tornado outbreak across the same areas tomorrow and night time event east of I-35. Monday along the I-44 corridor.

 

[Michael O'Keeffe]

The new 18z NAM keeps the boundary further north in NW OK, trending more with the GFS if this trend continues on the 0z then I'm pretty sure NW OK will be the place to be tomorrow. Looks like we could see at least a few nice discrete tornadic supercells in this region especially if a storm can stay just a bit south of the boundary and not cross it.

 

[Matthew Crowther]

The 18Z NAM is slowly but surely continuing the trend of moving the threat area a bit more to the north and even a tad west- strong signal of a triple point maybe even over in the far eastern panhandle- maybe Canadian or just north/northeast of there?

 

[Andrew Stoller]

I like what I'm seeing with the 18Z NAM. Further north a bit with the front, the cap is very strong through the day and totally erodes by about 5 pm. The NAM reflectivity looks like there is a few discrete storms that fire by 00z, so I don't think lack of daylight will be an issue, but more likely, 6 o'clock magic will be the outcome. There's a dot of 3km EHI of 6 to 7 right where the NAM initiates storms. The NAM has sped the system up a tad as well, so the speed sheer/upper level winds and 850 winds are all faster then previous model runs. There's also a small short wave/piece of energy that ejects out by the 00z-03z time frame directly atop the target area.

Looks like it will be a very localized/concentrated threat area. My initial target will be Canadian, TX.