05/31/07 FCST: CO / TX / OK / KS

[Bill Schintler]

Chase target:
Jetmore, KS (18 miles N of Dodge City).

Timing:
Storm initiation 5 PM CDT.

Storm mode:
High-based supercell storms, later evolving into a strong MCS which will track to the east during the late evening hours. Chasers may consider staying in Great Bend, KS overnight for an impressive lightning show after dark.

Synopsis:
Little change in the large scale pattern, which remains dominated by a slowly weakening, vertically stacked low over SD. At the SFC, an outflow-enhanced CF had pushed to the S of the Red River, and this provided the focus for a couple of pulse-type storms during the late afternoon and early evening hours. Further N and W, weak upslope flow and a H5 shortwave rounding base of upper low have resulted in scattered convection in ERN CO. SFC moisture was limited W of a CDS to ICT to TOP line where dewpoints ranged from the low- to mid-50’s with NWRLY LLVL flow.

Discussion:
The NAM, GFS, UKMET, and NGM were reviewed, and as has often been the case for recent day-2 forecasts for setups similar to tomorrows, the NAM solution was well south of the model consensus. Recent verification for setups with a H5 tough over the SCNTRL CONUS and SFC low in the OK panhandle has been trending towards the northward GFS solution.

Moisture return will commence overnight as a 25kt H85 LLJ develops into WRN KS, however the highest SFC dewpoints and deepest moisture will arrive in the target area by the time of storm initiation. The target is along the NRN edge of a shallow layer of 60F dewpoints. This will serve to keep cloud bases in the 1500-2000m AGL range. Tomorrow, SFC low pressure will become established over the WRN OK panhandle in response to lift in RRQ of 45kt H5 speed max coupled with strong SFC heating. A developing SFC WF will trail ENE of this feature with backing, up sloping SFC flow to its north, and forcing along and just north of this feature that will be the focus for severe convection. Deep-layer shear should be around 50kts, along with SRHs in the 200m2/s2 range. However, the aforementioned limited LLVL moisture will limit tornado threat. Overnight, a strengthening 40kt LLJ will aid in the maintenance of a strong MCS.

- bill

 

[Donald Giuliano]

Have been keeping an eye on Thursday, and I think it could be a setup that sneaks up on us a bit, with the area I'm most interested in being between Amarillo, TX and Liberal, KS. This is where the NAM is forecasting solid moisture to be in place by 00Z, with good low-level shear developing underneath decent 300-500mb flow as the sun sets. One feature I find especially interesting is a subtle 300mb jet max the NAM/GFS have consistently been forecasting to nose into the TX panhandle tomorrow evening, as this could help initiate isolated storms further south.

However, like many events this year, it looks like the most favorable tornado time would come around/after dark, as 3-4k uncapped CAPE is forecast to become juxtaposed with a strengthening nocturnal LLJ. It'll be interesting to see how this pans out, as it's hardly a synoptically evident setup so even slight variations in the verification will be magnified. Those qualifications aside, I do think as things stand now on the NAM there will likely be one or two good tornadic storms, with the potential for more should the system come out stronger than forecast. Of course, the GFS doesn't initiate any storms at all in the TX panhandle, and given the NAM's tendency to overdo precip, there's a distinct possibility that no storms will fire south of KS at all.

 

[Richard Halter]

Looks like our target will be colorado/tx/oklahoma panhandles intersection. The farther west we can catch these things, the better chance we have of daylight action. Ought to be fun!

 

[Warren Faidley]

Unless surface temps. rebound quickly, we might have the same issue of late, post-frontal cool inflow limiting tornado potential.

Initial target: Far NW corner Texas Panhandle.

Warren

 

[Mark Blue]

Our target area is Guymon OK this morning. We should be there in about 75 minutes. One of the local meteorologists in Amarillo TX thought the cold front was going to drift back to the NW as a warm front (retrograde) this afternoon, so if it does that just may be the triggering mechanism we need to break the monotony of the last couple of days!

 

[Andrew Stoller]

I'd also consider targeting Kim CO to Campo CO and then points east/southeast to Guymon. The NCAR WRF looks to break out a monstor supercell in southeast CO and move it east into southwest Kansas/OK panhandle. Points much further south look capped all through the day and into the evening.

 

[Donald Giuliano]

This morning's obs/model runs do not especially excite me. Plenty of moisture is available if a south wind would kick up for any length of time, but that's going to be tough given the lack of flow.

There's also a considerable amount of disagreement this morning between the NAM/RUC, and neither of them look especially fantastic. The NAM continues to insist on initiating storms around/after 00Z as strong vertical velocities through a deep layer erode the cap. Maybe that'll happen, maybe not, but either way there's quite a bit of uncertainty involved. It does look as though the storm mode will be supercellular during the day, though, which is a big plus. To me today is a bit of a crapshoot, but if it were the weekend, I'd probably be heading out since it's not too far from home, and any storms will be easy to keep pace with.

 

[Jeff Snyder]

My primary concern is timing of convection in the panhandles and southwestern KS. All three high-resolution, explicit convection WRF runs (3km, 4km, and 4.5km) break out discrete cells from east-central Colorado southward to far southwestern Texas. However, it appears that all develop storms off the higher terrain in eastern NM and eastern CO, progressing into the panhandles and southwestern KS only after 00-1z. I finally like the strength of mid- and upper-level flow, but I'm a little concerned about dewpoint deficits unless we get Tds into the mid-upper 60s which won't happen. As it stands now, it looks like we'll see 80-85F temps and 53-60F Tds in the western and central OK panahndle and northcentral and norhtwestern TX panhandle come 00z, which will put LCLs considerably above the 1600m that I use as a threshold for good tornado potential.

In addition, the 12z NAM has marginal 500mb flow over the TX panhandle at 00z, with better flow from OK panhandle northward. On the other hand, it, and the RUC, show a weakness in the 250mb flow over the OK panhandle, with a stronger jet streak to the north and a jet streak to the south. Regardlses, I like the shear profile from a hodograph-shape standpoint, and I think supercells are a good possibility. I'm not too hot on tornado potential, however. I like the area between Boise City and DHT, attm.

 

[Mitchell Daszewski]

If I could chase today I would position myself in and around LBB. According to RUC, look for a late show, however dynamics are there for the CAP to break and a big way today with possible high rewards.

Nose of sub tropical jet approaching at 0z with good difluence aloft. Mid level energy rounding the trough approaches a little after 0z. SFC to 850 winds are backed in response to height falls and strong heating, with higher DP's pooling against the dry line late in the day as it sharpens up.

I'm a TX chaser so I am a bit biased, however I believe the cap will blow in west Texas, you just have to wait it out. I'd expect some strong supercells to develop with possible tornadoes near sunset.

 

[Warren Faidley]

Yes, Lubbock area and eastern NM could produce a surprise today if the cap goes, or something initiates off the mountains. DP's in the 60+, "backed" surface flow and some upper flow (now) according to the White Sands profiler along with what appears to be a couple of jet streaks over the area. The SPC 5% tornado potential does extend down towards that area. I also like the warmer inflow and potentially lower cloud bases. The road network is better in that area than SE colorado. So, I might just base on I-40 west of AMA and be able to head N/S when things begin to pop. Today and maybe tomorrow are likely the last two "good" chase days in Plains for the near future.

 

[David Wolfson]

Pretty much what Jeff said. I like the upper diffluence between the cut-off low over the dakotas and the ST jet as the extra impetus. [V] Target: Dalhart, TX, for a late show.

[V] 20:00Z: Vis is showing development off dryline to the northwest on the NM/CO border. Good dews pushing into OK panhandle, with cap about gone. Still awhile before action further south IMO. Targeting north to Boise City - Elkhart - Johnson City, CO, to follow.
[V] 21:45Z: Am focused at Elkhart, KS. Impressive supercell params now bulls-eyeing in my vicinity with above storms still sorting themselves out to the northwest. On the edge of tongue of 60s dews. CIN about gone with MLCAPE pushing over 2k. Wait and see....

 

[Rocky Rascovich]

Flying solo

Finally able to post again after a multitude of computer/internet problems. I'll be doing my first solo chase today of the year and I'm targeting the Liberal, KS. to Scott City area for 0Z convective initiation.. Scott City could go around the 21Z time frame... discrete cells initially but I'm concerned with more uncapped atmosphere across that part of KS that a raging MCS will ensue an hour or two later.. still, tornado parameters may barely be met so one could get lucky today. Further south, based on the WRF, capping issues abound but still by 0Z we should see some action on the OK PH.. by 03Z, we should have a general MCS from north of Clinton, OK well north into KS. and I'll be hoping to try my hand at some lightning pics.
Hopefully my laptop will be functional and of course my handy dandy noaa wx radio... and I'm chasing in my honda which means I'll be excercising more caution than usual. If anyone is sitting this one out... call me for updates.
Rocky&family
cell: 405-226-2996

 

[Scott Weberpal]

Stayed the night in Liberal, KS and feel no reason to drift far from here. The 15z RUC portrays a nice dry punch just to the west and strong QPF signal by 21z. At this point I have no reason to look elsewhere unless later analysis says so.

 

[Stuart Robinson]

Agree with Scott. We are in Liberal, KS too and will not venture far. We will probably drift west-northwest to KS/CO border east of Lamar. I like the westerly winds in SE CO that will tighten up the moisture gradient there. Surface moisture is still a problem here so we will await the higher dewpoints from the south. Right now, we will target Johnson City, KS area. TM