04/05/05: FCST: Central Plains/Upper Mississippi Valley

[Tony Laubach]

Time to chime in here in regards to Tuesday...

I'm looking at ETA-40km at school on tomorrow. Running a ETA Composite, I'm seeing that they have a vertically stacked LOW centered just north of the KS/OK Border in Southcentral Kansas at 0z on Wednesday. They have precip breaking out well to the east and north of this stretching roughly from about Hays, following I-135 down through and east of Wichita and into the NE corner of Oklahoma.

Check this out from DDC's HWO at 1011am CDT..

A FEW STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE TUESDAY AFTERNOON AND EVENING OVER PORTIONS OF SOUTHWEST KANSAS NEAR A VERY STRONG UPPER STORM SYSTEM. LARGE HAIL AND AN ISOLATED TORNADO ARE POSSIBLE IN THE STRONGEST STORMS WHICH DEVELOP TUESDAY, MAINLY EAST OF A WAKEENEY TO DODGE CITY LINE. STAY TUNED FOR UPDATED FORECAST INFORMATION CONCERNING TUESDAY'S STORM SYSTEM.

I glanced at the 40km ETA and it does have the stacked low sitting just west of South Central Kansas just north of the border. They're thinking is east of a DDC to Wakeeney line. This seems a bit strong in their wording to me, but maybe I'm missing something. The 80km ETA has dewpoints wrapping around the backside of the low in the 50s, which that far west, isn't too terribly bad. All the rest of the good dynamics seem further east than that. I'm really not terribly sure where DDC is off with that mention. All the CAPE will be well to the east by evening.

I'm still uncertain about this trip, but the wording in DDC's HWO definately lies a temptation for us High Plains chasers as this would be an easy trip as opposed to NE Oklahoma. I'm still waiting on other HWO's and SPC's new Day 2 before I finalize my plans. I may also yap with other chasers to see what their thoughts are.. right now, I'm sitting at about 30%.

 

[Jeff Snyder]

Tony,
The only thing I can really think of is that DDC has in mind the possibility of some cold-core low tornadoes (similar to 3-21)... Low-level shear was strong that day, unlike tomorrow, so I'm not completely buying that possibility much yet.

I am still favoring the area east of a line from Ardmore, OK, to Dallas, TX. The NAM is still building 1500-2500 j/kg CAPE in this area by afternoon, along with decent low-level shear conditional upon surface flow not veering. South of the dryline bulge typically isn't the best place to be, but in the case of the stacked low as we'll have tomorrow, I think it's better than nothing. I'm sitting at about 70% for chase potential for tomorrow...

 

[Tony Laubach]

I've pretty much eliminated chasing anything east of I-35 for tomorrow, but some possibility exists. While slim, I'm eyeballing the areas in South Kansas, mainly west of I-35 to about Dodge City. SPC's latest Day 2 seems to hint that the best tornado chances are near the low as opposed to out east where they're thinking is high LFCs will dramatically reduce the tornado threat. On the other hand, where there is some potential, you find yourself playing in the grunge hoping to get beneath one of the embedded supercells in the crap. There is the potential for a dry slot to work its way into the area east of Dodge City, which will allow for better heating and hopefully give us some clearing to work with where some storms may fire in isolation before getting in with the rest of the arcing crap.

I'm in a holding status right now as I have talked with Colorado Chaser Verne Carlson about tagging up for the trip. For us, Dodge City would require about 5 to 6 hours of drive time on what would be for me less than 3 tanks of fuel up and back plus chase time. While we both see the situation as not the best, it has potential to give us a couple spin ups and gives me a chance to get my dry run in closer to home without so much risk. As I said above, I have pretty well eliminated chasing Southeast Kansas/Northeast Oklahoma. But with Southwestern Kansas a tiny player, it's worth a couple more hours to decide.

 

[Brett Adair]

I've pretty much eliminated chasing anything east of I-35 for tomorrow, but some possibility exists. While slim, I'm eyeballing the areas in South Kansas, mainly west of I-35 to about Dodge City. SPC's latest Day 2 seems to hint that the best tornado chances are near the low as opposed to out east where they're thinking is high LFCs will dramatically reduce the tornado threat. On the other hand, where there is some potential, you find yourself playing in the grunge hoping to get beneath one of the embedded supercells in the crap. There is the potential for a dry slot to work its way into the area east of Dodge City, which will allow for better heating and hopefully give us some clearing to work with where some storms may fire in isolation before getting in with the rest of the arcing crap.

I'm in a holding status right now as I have talked with Colorado Chaser Verne Carlson about tagging up for the trip. For us, Dodge City would require about 5 to 6 hours of drive time on what would be for me less than 3 tanks of fuel up and back plus chase time. While we both see the situation as not the best, it has potential to give us a couple spin ups and gives me a chance to get my dry run in closer to home without so much risk. As I said above, I have pretty well eliminated chasing Southeast Kansas/Northeast Oklahoma. But with Southwestern Kansas a tiny player, it's worth a couple more hours to decide.

I agree with you, Tony. It seems as if the best instability axis will setup from OUN-OKC-DDC-HYS just east of the stacked low formation. The low level moisture tongue will drive northward as the right entrance region of a vort max slides in. FCST SNDGs at OUN suggest things becoming very unstable there by 12z TUES. Almost 35kt of deep layer shear with LI's dipping to -6. SWEAT of 425+ will possibly make for some fireworks SE of the ULL.

OUN NAM FCST SNDGS

 

[MMartin]

Tony confirms my fear of the "embedded supercells" that this time of year often brings.

After getting burned this last Thursday, gas prices, and the fragility of this forecast, I am only optimistic enough to wander as far north as SE OK. With UVVs nicely stacked, a fair amount of helicity, and a baby CAPE axis stretching into this region, no reason to not be curious what will actually materialize.

RUC nailed this last E. Texas setup. Will be interesting to see what it shows in the morning.

 

[Tony Laubach]

We're going to gamble the low in Southern Kansas...

Verne Carlson and I are going to head out from Denver between 5 and 6 this evening for Dodge City, KS. Several non-weather factors came together for this.. first of all, Verne will be coming with me in my car, which means at 30mpg, we'll basically be splitting $25 for a full tank of gas, which makes this a rather inexpensive trip. Second, it's almost too close to not gamble; Dodge City, as I mentioned, is no more than 6 hours away, which makes it easy to get out and back. Barring issues with the pending Eastern Plains blizzard, we should be able to arrive back in Denver late Tuesday night, which all but eliminates me rushing to get back by 1pm Wednesday. Verne gets off work at 4 and will meet me at my place where he'll leave his truck and we'll head out to Dodge.

The forecast down there doesn't hold a ton of promise, but there is some hope. Mid 50s Tds are expected to push east and north of the SFC low tomorrow, which in the High Plains, isn't that bad. I think the shear could be better, which is my biggest concern, as I think there will be enough moisture to get storms going. CAPEs are running between 1000-1500J/kg which again, is good enough in this part the country. Anything tornatic will be very short-lived and weak, I'm afraid, but none-the-less, with as close to home as this is, it's worth the gamble. Personally, I'd stay away from areas in NE Oklahoma and far Eastern Kansas as I think tomorrow's best tornado potential will in fact be near the SFC low. And allow me to say, it isn't great (maybe 2%-5% probs AT BEST in this area in tomorrows SPC analysis), but I think it'll be the best for tomorrow.

Dodge City still looks like a safe bet to harbor ourselves for the night just in case the low drift further south. From Dodge City, it's only about 100 miles to I-70 to put us in position for storms up there (as DDC's AFD mentions this afternoon). I think we're safe to at least base of out DDC tomorrow morning and make adjustments as needed based upon morning forecasts.

The first chase of the year is 4 hours away!

 

[Nic Wilson]

I just took a peak at NCEP's 18z run of the NAM which just came in so take it for what it's worth. It significantly slows the low even more sitting it around the Enid, OK area at 00z tomorrow. The thing that concerns me is that the winds will veer much too early here in central OK and propagate the dry line out far ahead of the cold front. The NAM's precip. field has the dry line oriented southeasterly from the center of the low, initiating storms in the Tulsa region and pushing them to the northeast from there.

Moisture return is still not as good as I'd like either. Td's are in the upper 50's across southern OK and all of northern TX. You have to go south down to CCL to find a Td at 60. The event is coming together just as I expected, but it will be very sensitive as to the location of the dry line tomorrow. These strong surface winds won't help slow it down tomorrow either, but you can be sure that SPC will be moving the slight risk further westward later this evening.

 

[Mike Umscheid]

sfc to 850mb theta-e ridge nosing southwest towards the sfc low looks like a decent play tomorrow anywhere east of wakeeney to dodge city, like our (DDC) HWO suggests. 0-2km vertical vorticity along the inverted trof combined with low level cape in excess of 120 J/kg are possible... 0-2km lapse rates nearly dry adiabatic. These are the very things that Jon Davies really stresses in his research... it's all about low level stretching of vorticity if you have a strong enough updraft... sometimes, all you need is a good source of pre-existing vertical vorticity along a shear zone like an inverted trof north of the sfc low... like the models show tomorrow. It may be a hybrid landspout/supercell tornado kind of setup, but this is the reasoning we think there's at least a worthy enuf tornado threat to mention in a public product... Good luck to all who chase, I'll be at work (behind the radar probably..)

It's amazing how the NAM continues to trend toward the consistent UKMET/ECMWF. This goes to show how poor the NAM is beyond 36 hours. I rarely the NAM for anything beyond 36 hours.... or just use it's thermodynamic forecasts and mentally shift it towards the UKMET surface features..

Mike U

 

[Glen Romine]

I think tomorrow's best tornado potential will in fact be near the SFC low.

I think that is not an unreasonable plan Tony. There is certainly some possibility for this, in what will likely be a very small corridor, for some favorable convergence and adequate instability (the exact location uncertain but the pattern is probably feasible). Tornado threat appears limited by poor moisture and questionable deep layer shear to support long-lived convection. But, some of the higher resolution model guidance shows a dryline wrapping up nicely around the surface low with strongly backed sfc flow just to its north and east - with decent instability. It also shows considerable mid-level moisture wrapping around as well, which may limit the amount of insolation to the southwest. If this dryline surge indeed verifies there could be a small favorable window northeast of the surface low if convection can get going on the warm side, otherwise more slightly elevated convection should be likely back to the northwest in the warm advection regime. could see N to NNW cell motions with inflow on the southeast side of storms with cells along to just north of the dryline surge bulge. It is a long shot as you said, Tony, but if you've got the time why not? We'll look forward to seeing your reports.

Good luck,
Glen

 

[Gabe Garfield]

I'm somewhat torn between target areas...do I target the cold core low in SW/SC KS, or shoot for the higher instability that is progged for NE TX (18z NAM suggests CAPE up to 2900 j/kg)?

On 3/21, there was a more significant ageostropic component to the sfc winds due to the tilt of the low pressure centers with height. However, this particular system is expected to weaken (a vertically stacked low) which would result in more geostrophic motions and the veering of the surface winds. This in turn would result in weaker directional shear.

On the flip side, however, is that the instability will be significantly greater than on 3/21 (per the latest NAM). The shear should be more than sufficient for supercells (0-3 km SRH >150 j/kg), but nothing like the incredible 0-3 k values on 3/21 (on the order of 600 j/kg). I wish I had some idea how much each term contributes to the overall forcing for tornadic supercells. On the positive side, a 50-60 kt LLJ is forecast to develop by 00z over NE TX, which would greatly enhance the 0-1 km shear.

Gabe

 

[Rodney Price]

[/quote="Glen Romine" But, some of the higher resolution model guidance shows a dryline wrapping up nicely around the surface low with strongly backed sfc flow just to its north and east - with decent instability. [/quote]

My target area right now would be somewhere from Great Bend to Hutch. Sorry, couldn't select Harper Co., KS (not yet at least). I really like the cold 500mb temps on top of the surface features Glen mentions.

Any comments or concerns are greatly appreciated!

Mike U is dead-on with Jon Davies' work. Jon has done some tremendous stuff and features it on his web site. If you haven't checked it out yet, you should!

http://members.cox.net/jondavies1/tornado_...sprcll_tors.htm

I re-read this section of his web page the weekend of the 3/19 & 3/20, right before the 3/21 KS/OK event. It was a great refresher!!

Not sure if I'll be able to get out tomorrow. It depends on when I get finished with work. It should be an interesting day, so good luck to all who venture out!

Rodney

 

[Adam Atkins]

4/5

My target is Stroud, Ok tomorrow. The dryline bulge will be southeast of the surface low, which seems to strengthen from run to run. The NAM shows southerly surface winds, which I tend to disagree with, in NW Oklahoma at 1pm, while the dryline is in central, OK. The atmosphere usually doesn't work like that...so either the dryline push will be later on than expected, or the winds are incorrect, I tend to believe the latter. I imagine a Cu field will probably occur rather early on in the afternoon considering cold advection aloft will quickly weaken the cap near to the stacked low. This setup reminds me of April 20...I believe, 2003, minus the good directional shear. I truly believe directional shear in the lowest few kilometers can both determine the storm mode and tornado potential moreso than speed shear. High speed shear, low-ish CAPE days tend to form extremely tilted updrafts and short lived supercells/brief tornadoes, not to mention a bat out of hell storm speed. I doubt tomorrow's chances of having long lived tornadic supercells. More than likely I'll be suckered in by Mama nature to test out my new laptop/camera. I'd be surprised to see anything higher than a 5% tornado probability tomorrow.

 

[Mikel Shively]

Well I think I am going to keep it close to home tomorrow, no need on wasting prescious gas on this event, I think that any tornadic storms that do indeed form will be moving at unchasable speeds, I think that there will be tornadoes, I guess I am just not willing to drive the eight hours it would take to get in a decent area only to chase a really fast moving storm, would rather wait and look for another, slower moving storm.

 

[Jeff Snyder]

I still like the area east of an Ardmore to Dallas line, though I have many reservations... The best deep-layer shear is progged to be in this region, since areas farther north will be in much weak mid-upper level flow associated with the upper-low / trough axis. The best moisture (mid 60 tds) is progged by NAM to be in northeastern TX, but sfc flow veers slightly in time ahead of the dryline, which acts to decrease storm-relative helicity... The NAM is showing a 2500 j/kg CAPE in this area tomorrow afternoon, so I'm hoping we can just keep the southerly/southeasterly flow (no westerly component), since that'd be nice. Storm Motions from the NAM decrease from 45-50kts at 18z to closer to 25-35kts by 0z.

I am still concerned about surface moisture. The 60 degree Td isodrosotherm still seems to be looked south of Austin, TX, much to the disagreement of previous model forecasts (which had the 60 isodrosotherm closer to DFW at this time)... That means that southern/central/eastern Texas must maintain 15-20 mph winds through the night to get the moisture to the Red River by early tomorrow afternoon. We are definately going to need all the moisture we can get, since the EML, as seen on tonight's 0z FWD and OUN soundings, is very impressive (dry adiabatic from 800-550mb), so CINH would seem to be a player tomorrow, though the NAM depletes this by afternoon. The vort max seems to come through at a nice time as well, with it moving across I35 by mid-late afternoon. Linearly-oriented UVV max associated with this vort max may support squall line development, but the orientation of the deeplayer shear vector is forecast to be 45-70 degrees (by my eye-balling) normal to the dryline, so discrete cells may be favored.

 

[Bill Schintler]

Chase target for today, April 5

Chase Target:
Muskogee, OK

Timing:
Storm initiation: 2 PM CDT

Storm type:
Large hail to 1.5”; along with an isolated, weak (F0-F1) tornado report

Discussion:
A coupled UL jet structure will evolve into a separate NRN branch streak and SRN branch trough/cutoff low through the next 24 hrs. As the SRN branch system cuts off and slows down, MDLS are in good agreement of surface low pressure tracking from Perryton, TX to Woodward, OK between 18Z and 0Z. Associated with this will be a sharp dryline which will arc from an Enid, OK though 20mi E of OKC, through Durant, OK line at 20Z. Expect initial storm initiation between Ada and McAlester line around 2 PM in a region of maximum forcing in association, and just north, of a 250 mb “jetlet” rounding the base of the trough which will reach the area around 17Z. Chasers should look for a possible band of faint CI (SW/NE-oriented) along and S of an Ardmore to Mena (AR) in association with UL S/WV, which will proceed this initial convection. These initial cells will struggle and eventually weaken while more substantial cells will form about 50 mi to the N along the DL in the Henryetta area between 2 and 3 PM.

A potential negative factor is LLV cloudiness – 850 mb RH fields (NAM, GFS) suggest substantial ST layer through beginning of peak insolation hours, however look for 1-2 hours of good heating N/E of the dryline. This will result in T/Td’s of around 77/65 at the base of a moist layer extending upwards through 50mb along I-271, and increasing rapidly N and E of the DL, reaching a 120 mb along and E of a Bartlesville to McAlester line through 3 PM. MLCAPEs (100mb) will generally reach 2000-2500 J/kg, while SRH’s (0-3km) will reach 150-200 m^2/s^2. Shear is poor for storm organization because of the stacked nature of the system through it’s maturity, however LCL’s/LFC’s in the 800m/1200m range may support tornadoes in areas where storm/mesoscale low-level shear is decent.

- bill