5/10/10 FCST: TX / OK / KS / CO/ MO

[Mikey Gribble]

I can't believe everybody is being so quiet on this. IMO this run of the GFS is the best one yet. If the tornado paramater is any indication it is by far the best run with the tornado paramater getting all the way up to 21.7 and 23 all along the dryline. That is insane. 0-1km SRH is up to 620m2s2 ahead of the dryline. 1km SR winds were at 45kts. The 1km EHI is up to 9.8. Those are absolutely incredible numbers.

The 00Z NAM was great, but the GFS even takes that up a tiny notch. This continues to be one of the best if not the best setup I've ever seen. The only thing I don't like is 850mb winds veering a tiny bit. That's not cool, but everything else is great. I posted a short update on my blog so I'll just copy that here.

The GFS has started to come out. I only glanced over the basics on RAP, but everything looks pretty damn good with it. I really think this is probably the best setup its shown so far.
The dryline was running north and south from around Pratt to out west of OKC. Dewpoints were great with 65 all up and down the dryline. 850mb winds were out of the south at around 50kts. And it fires a storm right over south central Kansas. The environment that storm would be in is very favorable for violent tornadoes.
I feel a lot better now. I still can’t imagine the actual setup being as good as the models show, but if it did it would most likely be a major tornado outbreak.
After the a great GFS run tonight and a solid run from the NAM I would go with a moderate risk on the day 3 outlook. With what the models are showing now, this is a solid high risk day if it verifies.

 

[Eric Bucsela]

I agree - the 00Z GFS made me happy again. The shortwave is deeper and slower relative to the earlier run. And the params I saw look great (what site are you using for the GFS torn param?). If we can break the cap, it's gangbusters. Looking forward to what SPC says for Day 3 - maybe just a slight risk for northern KS lol!

 

[Chuck Robertson]

I too was pleasantly surprised by a slightly improved appearance to tonight's GFS run for Monday evening. I also like that fact that both the NAM and the GFS, despite significant capping issues, still show a convection signal for Central OK and SC KS. I agree that this cap will be breached due in part by the strength of the shortwave as well as its favorable timing.

Of interest to me is the NAM's insistence on a cold thermal trough just east of the low, extending southward from the bank of cold air in N KS to just south of Greensburg. I think this is caused by the model's belief that low clouds will persist in this area. I am hopeful that much of this area actually does see at least some sun, and thus some decent warming. If we can see about 80F over about 65Td near the warm front east of the low, then this truly could be a really big day.

I am believing, even more so with this latest data, that there is a good chance of at least a significant tornado or two in a small, relatively concentrated area (a sweet spot). However, I am still struggling to envision a large, widespread outbreak of major tornadoes. Temps to the north quickly become too cold, and temps to the south quickly become too hot. SW OK and points south from there may simply have T-Td spreads which are too large.

 

[Mike Smith]

Regarding the 06Z and 18Z model runs...

As I understand it, those models use the "first guess" (the six hour forecast) from 00Z and 12Z, respectively, along with ACARS data (temperature and wind data from jumbo jets in flight), profilers, VAD winds, and any soundings that might come in for their initializations.

The ACARS data is sufficiently dense that the 18Z NAM is pretty well initialized based on my experience (I have not done a systematic study).

 

[James Aydelott]

Regarding the 06Z and 18Z model runs...

As I understand it, those models use the "first guess" (the six hour forecast) from 00Z and 12Z, respectively, along with ACARS data (temperature and wind data from jumbo jets in flight), profilers, VAD winds, and any soundings that might come in for their initializations.

The ACARS data is sufficiently dense that the 18Z NAM is pretty well initialized based on my experience (I have not done a systematic study).

Mr. Smith is right, they're initialized by the previous synoptic run, and augmented by the sources Mike listed.

 

[cdcollura]

Good day all,

Monday is looking like "the day to be there" to me as well. I think the cap will not be a problem (It'll get eroded) and the slight "veering" of the 850 winds should not be a problem either (given the tenative location of SC Kansas as that is still over a KM AGL in that part of the country).

The verred (due south) 850 MB flow at 1 KM is fine, because winds under that layer should be backed, especially with the lee cyclone intensifying from 1000 MB in the morning and only 993 MB by Monday afternoon. Upper flow above the 850 layer should veer to WSW at 6 KM (500 MB) up. I also like the divergent flow at the 250 and 300 MB heights.

Enough said earlier on the EHI - Those numbers are rediculously insane. The nice triple-point / dryline bulge progged by the GFS (in SW KS) is also advertising dewpoints around 70 F ... Nice ... But I always take 5 degrees off that as it tends to over estimate those numbers, but 65 F is still good!

 

[Brandon Lawson]

I hope the 12z NAM is an indication of favorable timing of the shortwave and not just a tease. It's nice that it's showing convection popping up just after 00z. It has been consistent, at least for a couple of runs, in showing good 700mb vertical velocities in proximity to the triple point over southwest Kansas. 850 winds are still somewhat veered, but any storms over south central KS/ north central OK would be well ahead of the dryline. At 50 knots, I'm not sure if that would matter anyway.

EDIT: http://www.weatheroffice.gc.ca/data/model_forecast/622_100.gif (one can hope)

 

[Trey Thee]

There is still a pretty significant difference in the placement of the low between the 12z GFS and the NAM. It also seems the GFS has the severe parameters a bit further north than the NAM (in addition to being further east).

It appears that Monday will have supercells and tornadoes, but with the disparity in the GFS and the NAM I'm beginning to think that we wont see the models in good alignment until tomorrow night. It also seems that OK is firmly in play, at least north of I40 with perhaps a couple of supercells south of I40. All signs point to a big day across the southern plains.

At this point we still plan on targeting the Enid area initially for early/mid afternoon and then re-evaluate the situation. That should put us in a good position to move in any direction.

Why do I keep saying 00z? I edited to say 12z

 

[Brian Stertz]

Well focused event for Monday after 6pm...and it should pop before sunset given the magnitude of convergence and the inbound strong wave. My early line of doom is east of a Hutchinson KS to Enid OK line...and the supercells will move off the dryline and turn east-northeast into a strongly sheared and unstable environment. Triple point should migrate along or just north of the KS/OK state line Monday evening. I have adjusted my target to Harper KS and will head straight there Monday morning...maybe meeting up with Jeff somewhere in the afternoon to watch things. Although probably not on a scale of a tornado outbreak, this one has that well focused clustered tornadic supercell look and certainly that means 2-4 to hawk once they pop Monday around suppertime. They should rapidly become tornadic as the column shear is very strong bottom to top...with great veering and LL inflow noted.

 

[Jesse Risley]

I posted a more detailed forecast here, but I also believe that the strong forcing will be enough to overcome cap. Once the event draws closer, final differences regarding the placement of surface features will be ironed out.

I would hope that the overnight elevated convection would be out of the way in plenty of time for instability to rapidly build in the afternoon, and all of the models seem to indicate that this will not be an issue. I would be keeping a close eye near the low, as well as along any attendant dry line bulge. Even if the show is a bit late, the environment is primed enough that there should be a few decent TORs, given the very respectable SRH values. The overall restricted scope of the warm sector should preclude a "widespread" outbreak, but it could be a very decent play across the Plains on Monday evening.

 

[Travis Darling]

The NAM has been handling general forecasts better the past couple of days, so I'm more inclined to go with it. That said, I think initiation will be around 6:00 to 7:00 CDT (23-00Z) somewhere just west of I-35 and just south of the OK/KS state line. All the parameters (shear, moisture, lift, CAPE, lack of CIN) come together right there. I'm putting my money on Medford, OK, with road options to all four directions on the chance that I'm wrong.

 

[Russ Conlon]

Hi all. First time posting here and what an event to be posting on that looks to be shaping up on Monday. Latest, 12Z GFS and NAM seem to have an argument on position of the dryline from 21-03Z. GFS shows a much more aggressive push with the dryline just west of I-35 around 00Z. NAM seems to hang back in W OK and bulges along Highway 33 around sunset. I've never seen 3 Km EHI and lift indecies so intense. All the main factors that need to be in place are there. CAP of course is going to be the trick. I have two targets in mind with Enid, OK being the safe target and Anardarko or Chickasha, OK as the gamble target to compromise the GFS and NAM solutions. Forcing and convergence look incredible up toward north central OK and south central KS. However, I just can't help but think about any storm that fires south of I-40 will be the mother of all supercells and tend to be more discrete. I like the Chickasha target because of N/S Hwy 81 and I-44 maneuverability options. Regardless of where the storms go up, any one that goes up will likely put down some tubes.

 

[Michael Riedl]

What was interesting to me is that I thought 12z GFS would move the dryline a little further west to be more in line with the NAM but it moved it further East. In Fact Wichita is actually West of the Dryline according to the GFS. I keep Thinking that the next model run will be the run in which the models show more of a consensus but that doesn't seem to be the case.

 

[Trey Thee]

Hi all. First time posting here and what an event to be posting on that looks to be shaping up on Monday. Latest, 12Z GFS and NAM seem to have an argument on position of the dryline from 21-03Z. GFS shows a much more aggressive push with the dryline just west of I-35 around 00Z. NAM seems to hang back in W OK and bulges along Highway 33 around sunset. I've never seen 3 Km EHI and lift indecies so intense. All the main factors that need to be in place are there. CAP of course is going to be the trick. I have two targets in mind with Enid, OK being the safe target and Anardarko or Chickasha, OK as the gamble target to compromise the GFS and NAM solutions. Forcing and convergence look incredible up toward north central OK and south central KS. However, I just can't help but think about any storm that fires south of I-40 will be the mother of all supercells and tend to be more discrete. I like the Chickasha target because of N/S Hwy 81 and I-44 maneuverability options. Regardless of where the storms go up, any one that goes up will likely put down some tubes.

Russ I tend to agree with your analysis. As I mentioned earlier we're planning to get to Enid and evaluate.

Capping/dynamics will be more of an issue S of I40 but anything that does go up will be by itself. I could see one or two big cyclic supercells going up between wichita falls and I40. Given the environment, if someone were to gamble and head south, should something develop they could have a great storm to go after. Being further south initiation may be a bit later, after 7pm but the potential definitely is impressive.

I'm also fairly certain we'll see a decent size MDT come out on the day 2 tomorrow morning.

The models should I emphasize SHOULD, start coming together, although I thought that about this 12z as well and it didn't happen.

I also agree EHI and lift are quite impressive.

 

[Jason Boggs]

Gambling on chasing a lone discreet supercell may be a mistake on Monday. Monday may very well be a day that you get in position and let the supercell go by and hope it produces near your location. If one doesn't produce, try to get the next one in line. Staying up with 1 lone supercell moving at 45 0r 50 mph will be downright difficult. Best scenario is a string of pearls up and down the dryline for better success and to distribute the chasers a little better.

It really is tough right now to even come close to pinpointing a target. I do agree that a lone supercell south of I-40 in a more capped environment may be big and discreet, but it just won't be worth it. I think it's better to start north and let the cells mature and come your direction.

Things are still on tap for a big day Monday. Everything is in place for possible strong to violent tornadoes. Monday will be a day to glance at radar, but don't depend on it! Don't get caught in that trap. Keep more of a focus visually, and on your next road option and escape route. Everyone stay safe out there!!!