06/12/05 FCST: Plains

[Ben Prusia]

12Z NAM showing a 995mb surface Low Pressure system and associated triple point heading into central Kansas at 0Z Monday. Dryline is progged running down from the Low Pressure to just east of the panhandles of Texas and Oklahoma. Moisture, being really cut back from the new Tropical System in the Gulf is progged to be around 60-65 degrees throughout Kansas and Oklahoma, and appears to be a modified continental air mass at the moment. Thus with lower moisture availability, SBCAPE values will be much lower, in the range of around 2000 J/Kg, but there will be modest CIN in KS and OK. ENE of the associated triple point, progged 0-6km shear values of 50 kts will be located throughout NC Kansas. SRH in front of the dryline, with good 0-3km values of near 500 m2/s2 in NC Kansas. A factor that may help initation will be the better support of winds at the 850/700/500mb levels, with progged 850mb winds of 30-50 kts to the south-southeast to due south in central KS running into OK, and progged 500mb winds to the south-southwest at or near 50kts for most of central KS and Oklahoma. Much better turning will be located up in NC Kansas, thus better shear. Looks like NC Kansas, at least along and north of Interstate 70, south of a progged warm front and east of the Colby/Oakley areas are a good bet as of this time.

Graphic for this forecast up at "My Chase Forecasts" below.

 

[Jeff Snyder]

Moisture, being really cut back from the new Tropical System in the Gulf is progged to be around 60-65 degrees throughout Kansas and Oklahoma, and appears to be a modified continental air mass at the moment. Thus with lower moisture availability, SBCAPE values will be much lower, in the range of around 2000 J/Kg, but there will be modest CIN in KS and OK. ENE of the associated triple point, progged 0-6km shear values of 50 kts will be located throughout NC Kansas. SRH in front of the dryline, with good 0-3km values of near 500 m2/s2 in NC Kansas.

My main concern with this weekend's activity continues to be the tropical system in the Gulf. We've seen it before -- subsidence on the periphery of a topical system dries out the low level airmass. This, combined with northerly flow to the west of the cyclone, really destroys our source region. If the low-mid 60 Tds are all we can muster, I don't think we'll see much of a tornado threat owing to the very high LCLs. We really need the >70 Tds this time of year courtesy of the warmer 850/700mb temps that are common in mid-June in the central Plains.

 

[Michael P. Morris]

After May 11 I don't touch warm fronts in northern Kansas, so I will likely target the Western Oklahoma dryline on Sunday if the 84 hour ETA verifies. I would be a little happier if the dry punch at 700 mb was displaced farther ahead of the dryline, overlaying that nice region of veered 700/850 winds. Choosing an exact target at this time is kind of tough, but I would probably choose somewhere between Alva and Woodward as a lobe of vorticity may provide enhanced lift as the day progresses.

 

[Anthony Petito]

For those interested:

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0346 AM CDT THU JUN 09 2005

VALID 121200Z - 171200Z

SPC MREF DATA WAS UNAVAILABLE FOR THIS FORECAST.

...DISCUSSION...
STRONG UPPER WAVE WILL LIFT ACROSS THE CNTRL/NRN PLAINS AND UPR MS VLY JUNE 12-13. PREDICTABILITY IN THE EVOLUTION OF THE UPPER PATTERN BREAKS DOWN RAPIDLY AFTER THIS TIME WITH ECMWF INDICATING A CLOSED LOW DEVELOPING OVER THE CNTRL PLAINS BY JUNE 14 BUT THE GFS KEEPING A PROGRESSIVE AND MORE ZONAL FLOW ACROSS THE CONUS. GIVEN THESE DIFFERENCES...SEVERE WEATHER FORECAST BEYOND ABOUT JUNE 14 IS UNCERTAIN.

No mention of the happenings in the Gulf however.

 

[Adam Atkins]

6/12

A dry punch at 700 mb might steepen the lapse rates just a tad, but that does a minimal job with this setup. The only dent in the picture might be the current tropical storm in the eastern GoM would decrease the surface moisture by 5-10 degrees F. With extreme shear like this scenario, high CAPE is favorable for balance and to prevent too much forcing and a linear storm mode. A negatively tilted trough with 60-70 kts progged at 500 mb and SSE low level jet at 40 kts via the NAM is sufficient in my opinion for violent, tornadic supercells acros the Southern Plains. What I appreciate about this setup is there is a decent cap to prevent too much storm interaction like last Saturday. Isolated storms also prevents a widespread damage risk and Sunday appears to have the potential for strong tornadoes at this point.

For those of us who have been craving a textbook western Oklahoma chase, Sunday looks like a doozy. Let's hit I-40 westbound.

 

[Douglas Mitchell]

I'm only posting one picture for my forecast, I hope it justifies not having an actual forecast so to speak. I saved it to my photobucket account for posterity.

Scary stuff I tell you.

 

[Nic Wilson]

For those of us that have to work M-F during summer and the heart of the 2005 chase season this has been a tough week to watch from the sidelines, but never fear -- Sunday is looking pretty good. Here's my forecast.

Tour of the Models

ECMWF - Nice SSW-ly flow out ahead of the strong negatively-tilted trof, with the base near the four corners region at 12z. The negative tilt and upslope flow in Colorado produces cyclogenesis as expected in southeastern CO / southwestern KS area.

NAM - The most progressive of the models focusing the surface low in the panhandles and breaking out intense convection oriented SW to NE across Kansas from this feature. Peak 500 mb ~35-40 knots is located in this same general vicinity with great veering winds profiles, as the sfc low will focus winds from the ESE across a broad area of KS.

GFS - Much more in-line with the ECMWF with slower progression of the trof. A strong 997 sfc low is progged in southeastern CO/southwestern KS and will be the focus of the day's events. 500mb jet max doesn't round the trof until late in the day which should place the emphasis of supercell formation thru central Ks up to the I-70 corridor.

Synopsis - Expect the slower ECMWF/GFS solutions to verify....the effects of the MCS later tonight and the gulf sfc flows due to Arlene remain to be seen, but don't expect them to damage the moisture potential too badly. GFS is ambitious with 70 Tds in the area of interest, but I think mid 60's are reasonable. Should be interesting to see how the mesoscale features set-up over the course of the next 48 hrs.

 

[Anthony Silver]

NAM seems to have a better handle on Sunday's setup. I've lost faith in what the GFS is predicting since it has been really screwy during the last few days.

 

[Adam Atkins]

6/12

Well if the NAM has a better handle on Sunday's setup, we'll have a lifting negatively tilted trough, which means weakening wind fields with time, and can spell HP or non-tornadic storm chasing. The 00 utc GFS actually looks great with a surface low on the SE CO/SW KS border at 999 mb and backed SE winds all along the dryline. The backed low level jet excites me as well, which tends to happen with negatively tilted troughs. A 50-60 kt mid-level jet streak per the GFS would be awesome, yet the NAM shows a 40 kt max at 18 utc, decreasing as the trough lifts to the northeast to 30 kts by 0 utc. I'll take an average of these models and still get marginally excited about Sunday.

Colorado upslope also looks like a good bet for Sunday if you're in the neighborhood! I'll be taking work off and probably be heading towards wherever the northeast side of the surface low sets up. Hopefully Arlene gets her big fat a$$ out of here to prevent recycled air from impacting our CAPE on Sunday across the Great Plains.

 

[Anthony Silver]

I guess for now I'll stick with the NAM. I'll have to wait for future GFS runs and compare the two before i make any determinations. I kind of have doubts whether Arlene will have any impact on the Central Plains. I guess it all depends on what track she decides to take. Looking over the last 3 day advisory issued by the NHC...it appears that she will track into the Ohio valley by Sunday, if this ends up being the case, I dont think it will have much effect on the plains. Now if she tracks farther westward, we could be looking at some problems.

 

[Glen Romine]

....Looking over the last 3 day advisory issued by the NHC...it appears that she will track into the Ohio valley by Sunday, if this ends up being the case, I dont think it will have much effect on the plains.

I had felt this way earlier - but that was before I thought it would end up as strong as it is and as far west as it has moved. If you follow the trends in the low level jet strength over the progressive model runs - there has been a substatial hit that has eveolved owing to the loss of pressure/height gradient west of Arlene. Combined with other unfavorable trends in forecast evolution, this is a brutal hit for significant tornado potential with the OK/KS system if the NAM forecast evolution is going to be realized. So, you a) hope the solution is bad -or- B) plan to chase HP weakly tornadic supercells. Maybe this morning's runs will start to rebound and give a more optimistic outlook.

Glen

 

[Tony Laubach]

Looks like Jon and I are going to be on the road by 6am heading for
either Liberal or Dodge City. Pending what the surface is shaping up
to be later in the morning, I'll decide whether I need to blast south
or just stay ahead of the dryline. I am 90% confident on an initial
target along the KS/OK border someplace between Liberal and I-35,
althought I am keeping my options open for something in the extreme
Northern Texas Panhandle. I want to be on the road with enough time
to make that venture if it proves to be warrented. I'll be on the
phone with a lot of nowcasters tomorrow to help me decide whether that
to be needed.

As for my forecast tomorrow, I'm pretty much throwing models and such out the window.
The variance between the different models and the runs
indicate to me that nothing has a grasp of what's going to happen
tomorrow. A lot of tomorrow' setup will rest on the hands of what
goes up today. Cold pools can kill off instability or left over
boundries can add focus. Also, the timing of the trough and movement
of the fronts and dryline will also greatly affect tomorrow's setup.
While I'm confident that we won't cap bust, its hard to say what will
result from tomorrow. In any case, I think our best chances lie
south. Upon arrival in Colby tomorrow morning, I'll take a look at
surface obs and other information over a quick breakfast and pull the
trigger on a southern Liberal target or a more easterly target in
Dodge. Both leave me options to go anywhere, but I want to know
whether I need to blast south or just stay ahead of an approaching
dryline.

I am skeptical on Eastern Colorado's setup for tomorrow as I think
instability will be limited and severe storms won't be as likely. Not
to say it won't happen, but CAPE values don't look to exceed 1000
anywhere in the state. If you can believe the ETA's 36hr forecast of
CAPE, there isn't anything higher than 800 anyplace in the state.
Using the same map, there are bulls-eyes of CAPE right near Dodge City
in Kansas as well as Western Oklahoma. Both with values of 2500J/kg.
The SRH doesn't match up well with either of those bulls-eys with the
better values east of those CAPE maxes. As for moisture, the 55F
isodroatherm (sp?) sits right along the CO/KS border with values
increasing to the east with 70s stretching from about Pratt southward
into Oklahoma.

500mb flow over the areas show mid 20s to upper 30s over Colorado with
slightly increasing speeds over the Central Kansas area southward to a
40kt max in Northwestern Oklahoma. There is a vort max sitting near
Liberal along the KS/OK border at 0z Monday. Shear down to the
surface looks pretty good with 850 south of the SSE.

This all of course could mean nothing if the convective messes
overnight don't clear out in time. Heating will be an issue tomorrow
if clouds stick around and could quite easily kill chances in a
hurry. I'm happy with my preliminary target and may find that I don't
move much from Liberal or Dodge; in any case, I think extreme Southern
Kansas holds tomorrow's best chance. While this particular setup
doesn't leave me wanting to rely too heavily on the models with the
uncertainties of tomorrow, my judgement combined with what I'm seeing
has me happy with this... for now!

 

[Kiel Ortega]

I will agree with Tony and say the NW OK/DDC/KS-OK line looks ok. If maybe there is a speed max not picked up by the models and embedded in the flow (however, looking at the water vapor loops I ain't seein' this!), it could make things a little more better for tomorrow. While the models have been off, they seemed to have agreed quite nicely in the 12Z runs. However, if the wave decides to kick out early (the models have it rotating out rather quickly and rather NORTH!) tomorrow is a nice drive in the country. The models do have sub-700 mb levels done nicely for tornadoes.

In terms of the thermo, it seems we gonna need some lapse rate help especially in the 900-~700 mb layer. The 12Z AMA sounding made me gag as the nearly moist adiabatic lapse rate in that layer scared me (given the amount of convection yesterday, I would assume these lapse rates are over my current target area--and today's cloudiness probably won't help!). However, looking at the 18Z FWD sounding relieves my worries a little and it seems the deep moisture is still in TX so any Arlene concerns should be gone..especially if the winds in that layer can back and blow those type lapse rates and moisture back to the target area. LMN soundings will be a nice thing to have tomorrow.

Tomorrow will tell the tale....

 

[Joey Ketcham]

Basically my thoughts would be a repeat of what everyone else has already said... I'm planning on heading out early AM from Pittsburg, KS and make my way along the KS/OK border out west...

 

[Nic Wilson]

Target: Scott City, KS

This is a tricky forecast with the arrival of the upper-level jet maximas tomorrow afternoon. All the areas of interest tomorrow will suffer from backed jet winds above 500mb which in turn is hurting the models chances of supercells, but I feel more confident in the areas further north and a tad west of the TX/OK panhandles where the 70 kt+ winds above 400mb will be in place and should allow the supercells to ventilate and sustain themselves. The large question mark is how much moisture will be in place in areas along the HW 83 corridor north of Liberal. Current Tds are only in the low to mid 50's, but intense cyclogenesis tonight and early tomorrow should advect in the quality moisture by mid-afternoon and create the features necessary for tornadoes. The lack of data stations in this area limits the models grasp as well, so forecast soundings etc. are of little use. I would like to stay kind of close to Colorado as well with my choice of set-up so that is swaying my decision to stay further north. Tremendous shear and likelihood of LPs near my target area have me intrigued...of course cloudiness, residual outflow boundaries and the instability potential are things that can only be looked at and taking into account in the morning, so much like Tony I plan to check data in Colby and readjust south from there. Good luck to everyone out there tomorrow -- I'll be driving my gf's White Explorer with NE plates so say hello if we see you!