6/16/06 FCST: TX / OK / KS / CO / NE / IA / MN

[Jonathan Whitehead]

Models getting more aggressive bringing in the west coast trough into the aforementioned area on Friday. Both the GFS and the model previously known as the ETA are almost in exact agreement in increased upper flow with this system with SLY 850 winds progged at or around 30kts veering to the SW at 35-40kts at 500 and 300mb winds at 50-60kts. Also, dwpts in Gulf have rebounded rather dramatically to the 70s but return flow is not forecasted to occur until day of. ATTM CAPES are only forecasted to be modest at best (~2000J/Kg) but depending on how much moisture return we get into the region, that could go up.
Also, probably of most importance to a lot of people on here is the cap. The west coast trough will push the SW ridge into the Baja and flatten it out s/t the cap will not be an issue. It looks to be a significant bet storms will fire. As for tornadoes, the threat doest not appear to be all that high attm, esp with forecasted storm motion vectors, but, as always, early on, depending on discreetness of supercells, it is a possibility that can not be ruled out. ATTM the target area appears to be in western half of TX, OK, & KS.
will keep monitering.

note: might need a chase partner

 

[Tom Dulong]

Thought I'd make a pitch for supercell and tornado potential in southwest KS/southeast CO for Friday.

Checking BUFKIT forecast soundings in the central high plains, GCK seemed to have the best potential, Here is the CONRAD storm type summary for that location at 17/00Z:

A Convective Storm Matrix

SUMMARY I2

1/4 curve to 2.5 km, Linear to 7.5 km,
Us = 60 m/s, Moderate CAPE

Strong, dominant, cyclonic, right-moving supercell:

The initial cell splits, with the cyclonic right-mover dominating. Significant surface rotation also develops with the cyclonic supercell by 2 hours. Ordinary cells are generated along the left-flank gust front, but the very strong shear relative to the cold pool circulation limits their growth and they remain weak.


Of course, for this to occur the CIN of about 100 would need to be overcome by strong forcing.

Definitely something to chew on.

 

[Jonathan Whitehead]

After reading through various discussions (OUN-AFD/SPCD2) it appears that everything is to occur as I originally saw last night. The only difference now is that precip is likely to develop overnight in NW Oklahoma and continue into Friday. Will need to monitor for outflows/mesoscale boundaries that this precip area puts out which may affect convective potential outside this precip core. Also of note is that strong deep ascent is progged to spread into the TX panhandle across the dryline where more discrete storms are likely given increased capping across this area. Right now it appears that surface moisture will be limited/modest so not expecting any respectable threat for tornadoes. It appears that by late evening convection in KS/OK/TX will come together into one or two nocturnal MCSs and spread eastward from there and maintain intensity as result of LLJ and increased height falls.

With that in mind im monitering two areas for a target for tornados and high end severe potential. One in SW KS and the other along dryline in TX panhandle. Right now im leaning toward TX panhandle due to increased capping which would result in more discrete storms. Will keep monitering

and still looking for chase partner

 

[Bill Schintler]

Discussion:

Nothing really flips my trigger about Friday. A quick look at things, and the best target I can find in the country would be an area between Perryton, TX and Liberal, OK. There, an outflow boundary and dryline interaction should provide the focus for moderately severe storms as a surface low strengthens near Amarillo. A mid-level speed max (H7 flow approaching 40kts) on top of backing SFC flow to the N of the low should result in favorable hodograph curvatures and bulk shear. Timing for storm initiation will be 4 PM CDT. A potential negative factor will be storm development further to the south along the dryline towards AMA and LBB, which will likely evolve into a multicell mess early given relatively low convective inhibition. Because of this, a short window of opportunity may exist for supercells in the OK panhandle.

Further north, widespread convection and associated cloud cover will be in place early in the day thoughout much of MN, SD, NE, and KS; as a result of a slow-moving cold front beneath upper-level ridging. One possible area to consider may be just east of Sioux City, IA. This area should remain cloud free throughout the day, allowing for destabilization by mid-afternoon as a vorticity ribbon approaches from the SW. An outflow boundary from earlier convection will likely exist in this area, and it appears as though a weak mesoscale low may form in the OAX area, possibly resulting in backing of SFC winds in NWRN IA. In any event, Iowa looks like a very marginal setup Friday.

- bill

 

[samuel stone]

I see dont see any thing I like about this set up (other than drought relief). I am not going to get into detail other than to say what I dont like aboout it. 1) high t/td spreads, 2) essentially Unidirectional flow from 700 - 300 milibar parralell to linear forcing associated with front.

Definently not chasing (tired of marginal set ups), I am just looking forward to some much much much need rain. BTW, ICT calls for 2-3 inches of rain across central kansas!

 

[Jeff Snyder]

I don't really know what to make of the forecast for tomorrow. Models remain consistent in dropping dewpoints into the 50s ahead of the dryline and front across the OK/TX panhandles. Given the backed 250mb flow in north of the panhandles, and a deeplayer shear vector parallel to the front, I'm more inclined to investigate the OK/TX panhandles, where flow aloft will be a little more veered. Current surface obs across TX show a rather sharp dewpoint gradient, with dewpoints quickly rising above 65F southeast of a line from Del Rio to Shreveport. Fortunately, sfc flow remains strong even at 11pm, with 10-20kts southeasterly flow, indicating that the greatest possible advection is occurring (with flow parallel to the gradient). In addition, there is a very strong LLJ in place, with mesoanalysis indicating >55kts at 850mb across parts of western KS and the OK panhandle, decreasing to 30-35kts in central Texas. In addition, the DDC VWP is showing 60-65kts at 3-5kft! That's one heck of an LLJ considering it's only 5z. Moisture depth has increased nicely along the TX Gulf coast -- for example, the 0z CRP and BRO soundings showed a moisture depth of 75-100mb (an improvement of 40-50mb on this morning's 12z soundings). For the first time in a long time, true Gulf moisture is in the process of advection into the Plains. Despite this, it appears that the models are forecasting rather significant vertical mixing, which results in dewpoints dropping near sunrise and shortly thereafter. If this indeed occurs, LCLs will be very high (>2000m), which will likely result in high-based, outflow-dominant convection (gee, we've heard that plenty this year). In addition to creating high LCLs/LFCs, the marginal dewpoints being forecast by NWP models yield only moderate instability (1500-2000 j/kg). While low-level will be backed by normal standards, upper-level flow will also be backed, which had been (per 12z forecast soundings) resulting in "N"-shaped hodographs. Again, we've seen this quite a bit this year -- veering wind profile in the low-levels, with backing wind profile in the upper-levels. Oy.

The timing of the main vort max will be favorable for late afternoon initiation along the dryline. Both the NAM and GFS indicate that there will be a thin ribbon of high (relatively) vorticity in the far eastern TX panhandle by 0z, from which we can deduce DPVA near the OK/TX panhandle border region in the late afternoon (DPVA yielding upward motion, helping to steepen lapse rates and remove capping). Again, with the threat of widespread convection in KS and northward (along with the very backed upperlevel flow and deeplayer shear vector parallel to the front -- linear mode), I'm more inclined to target the TX panhandle. OBviously, sfc obs tomorrow will be very important, but my primary, initial target zone is the area bounded by Childress to Groom to Floydada, but that'll likely shift when I look at morning obs.


EDIT: latest 3z RUC run is picking up on my suspicion about low-level moisture. The 12hr forecast valid at 15z tomorrow is now showing >65F dewpoints east of the the OK/TX panhandle border and south of a Lubbock to Childress line. This makes MUCH more sense given the very strong, backed LLJ and current obs. Naturally (and physically), the dewpoints will drop by a couple degrees as it advects from central TX into the panhandles, given that the dewpoint "lapse rate" is negative (so the dewpoint drops as the parcel increases in elevation -- mixing ratio is conserved, however!). If we can get dewpoints >65F up to the dryline, however, I'll be very happy.

 

[Amos Magliocco]

I agree that the potential for a better than advertised BL moisture profile is amazing given the standard mixed-out CAPE-robber routine this year. Low level flow has been strong for several hours now and as Jeff mentioned, the LLJ is cranked. I believe some dewpoints will mix out, of course, and that our Td-T spread will remain prohbitively high for tornado chances, but rotating storms along the dryline seem very possible. Given the shear profiles on forecast soundings from Pampa to Guymon, these could be good-looking storms before they grow too outflow dominated.

For more wishcasting encouragement, the 0z GFS paints a rosy picture of the dryline evolution and aggressive mixing eastward, with a bulge into the northern Texas panhandle and nicely backed flow to the northeast.

If we get some high clouds to keep temps in check or an outflow boundary in the neighborhood, with the forecasted vertical motions and CVA, the tornado chance is not zero. (ringing endorsement, eh?) I'll probably head for CDS in the morning, do a Kettle wifi check, then turn north for Pampa or even further.

AM

 

[Sam Barricklow]

I'll probably head for CDS in the morning, do a Kettle wifi check, then turn north for Pampa or even further.

Amos is right on. A second area of interest from a shear perspective will be the northeastern Texas Panhandle into southwestern Kansas, perhaps as far north as the Dodge City / Garden City area. Moisture may be an issue, but time will tell.

The low level jet is screaming across Fort Worth this morning. Surface winds are light across Garland, but the dew point is 71 degrees! The wind is only 5 MPH from the southeast right now.

If I chase, I will not be able to leave Big D until after noon.

Storm motion should be NNE, with supercells turning more northeasterly, or perhaps ENE if wildly deviant motion occurs.

Good luck to all who chase.

 

[Brandon Ivey]

I will be out there trying to salvage what I can out of today's set-up. I like the fact that this system has some good dynamics for this time of the year, but with every other system so far it is always that one key ingredient that is missing. Today, that would be PBL moisture which is also going to contibute to more convective downburst and possibly outflow dominate cells. It was 74/60 in Garden City with a SE wind and 70/60 at Elkart (with rain in the area) at last check...if that were only true by this afternoon! That late June sun with such a high angle will get to cooking things here soon once those clouds move out of the region. still Tdd will be a little lower than yesterday! I should stay home and get all this homework done I have piled up, but I want to chase so I will be heading west! Good luck to all.

 

[Adam Atkins]

For all of you targeting the panhandles, you might want to rethink and go for a more southern target. The cap will be stronger, the mid level flow is more veered, the upper level venting arrives in time, and the surface winds are sufficiently backed. The play might be a tail end charlie today in the Lubbock to San Angelo vicinity. I am sitting out because I doubt the moisture quality, however if storms are able to stay discrete and move far enough to the east, there could be a better tornado threat. The most exciting thing about today is seeing a mid and upper level wind magnitude above 25 kts. Good luck folks!

 

[Kurt Silvey]

Well I'm not going to the TX panhandle, so we’ll have to make due with what we have here in NE. This morning we have mid 60ish Dp’s across the eastern ½ of the state with a good LLJ (40-45kt on fbyn profiler) we should be able to maintain these even with some mixing. I see two areas of interest; the first is in south central NE around and south of Holdrege to Alma, the second would be in ne NE and nw IA. The southern area is forecast to have better deep layer shear (~40 kts), but lingering morning convection could pose a problem if it doesn’t clear out soon. The northern target will have greater daytime heating and possibly higher Dp’s, but the deep layer shear stinks. I can reach the southern target in about 3 ½ hours, so I will wait until 17z before deciding. I would like to go sw as that also opens the option of dropping into nc KS if need be. I Think there will be good storms up north, but without any deep layer sheer it will be a big HP mess. Good luck to all.

 

[Jeff Snyder]

The most exciting thing about today is seeing a mid and upper level wind magnitude above 25 kts. Good luck folks!
[/b]

I'm still leery of KS owing to the nearly-southerly 250mb flow up there. I've chased in the whole 'veering lowlevel, backing upperlevel' environment this year, and it's tough to keep discrete activity (though it does signal destabilization). I guess it comes down to whether the RUC or NAM 500mb flow will verify... Given strong 850mb flow, the NAMs forecast of only 30-35kts at 500mb is yielding only ~25kts 0-6km shear in the warm sector, which is very marginal supercell shear. The 12z RUC, on the other hand, is indicating 45-55kts at 500mb, which is creating 35-45kts of 0-6km shear. I do agree that the southern play (south of i40) seems to have the best discrete cell potential, which is also indicated in the 4.5km explicity convection WRF from last night. I think the RUC is overmixing the southeastern TX panhandle area (showing <60f tds and >100F temps), given that mid-60 juice is not too far to the southeast. My initial drive-to target is Shamrock, but we're goig to stop there and reassess, either heading southwest or north as necessary.

 

[Jason A.C. Brock]

Ill be out chasing the panhandle. Im gonna try to stick to an area SW of AMA.I had a longer report but got kicked off the server., If the Holy Tornado guys see me stop by to say howdy. Also my call is KE5HZA and you other guys can give me a call. You have my number

Headed for CDS AT 11:30AM

Jay

 

[Kiel Ortega]

the NAMs forecast of only 30-35kts at 500mb is yielding only ~25kts 0-6km shear in the warm sector, which is very marginal supercell shear. The 12z RUC, on the other hand, is indicating 45-55kts at 500mb, which is creating 35-45kts of 0-6km shear. I do agree that the southern play (south of i40) seems to have the best discrete cell potential, which is also indicated in the 4.5km explicity convection WRF from last night.
[/b]

Nothing much to add here...though looks like the RUC is right on with the winds per the area profilers. I like the E TX Panhandle. Kinda curious about the models though...they all have been fairly stubborn about giving the surface winds any sort of easterly component. Definitely would like to see the cap stay as long as possible...the RUC has some pretty good vertical motions all over and if things start popping early, it's gonna be a mess. Good luck to all who are out.

 

[Jeff Snyder]

Dan Dawson and I are sitting in Shamrock (thanks Best Western).... To out severe disappointment, dewpoints have mixed out a bit, with Tds largely in the 55-59F range in most of the panhandle(s). A new cell has evolved in the mess of low-echo cloudcover and light precip between AMA and LBB... After looking at obs and latest model guidance, we're hoping to get a cell south of I40 into far western OK by dusk. 18z RUC, 12z 8km WRF, and other guidance suggests that the best low-level shear and instability will be present along and just east of the OK / TX panhandle border region by 0-2z. We are also encouraged by the stronger-than-NAM-forecast mid-level flow. I'm still concerned about squall-line mode, but I guess we have to deal with what we have. With flow aloft become more backed to the n orth, we're still liking the area south of a Borger to Canadian line, and preferably south of I40 (in the more veered upperlevel flow).