10/19/05 FCST: Plains

I too was originally thinking that this would be a more northern system but the GFS and especially the ETA have the low taking a much more southerly track. If the GFS verifies, it will be very reachable from my home in Denver, CO. I am currently hoping for a target of Dodge City, KS but if the ETA verifies it would be more like the OK/TX panhandle border area.
 
I think supercells are likely, but I don't like the tornado potential. I believe the NAM is overdoing it with dewpoints >65. I think upper 50's and low 60's are more reasonable. I have no idea on the depth of the moisture since I haven't looked at any soudings or forecast soundings. The only thing I really see preventing the possibility of a few tornadoes is LCL's being high. Earl's model page(NAM) shows storm motion as easterly(it is hard to tell because of the map scale), but I would think more of a NE motion would be right. I am probably going to end up chasing since it isn't too far from home and one more chase would bring closure to the season. Unless moisture can increase(I don't know where it would come from), then I think all we can hope for is some good structure, but I wouldn't be surprised if we get one or two weak tornadoes out of the deal(5% sounds about right). Right now my pre-chase target is Woodward.

Andrew, what are "ascending Mid-Level Lapse Rates"?
 
I am not really concerned about surface moisture. The 60 degree Td isodrosotherm is progged to be as far north as southwest KS... I pretty much like the area from about Claredon, TX and then points a bit further northward, near the surface low, which per the latest NAM lands in the central TX panhandle by afternoon. Mid-upper flow is strong across the panhandles, and the speed/rotation is good throughout the layer. I would like to see better 850mb flow, but the 20kts will probably do the trick... Moderate CAPEs (1500-2500), moderate deep-layer shear, and decent storm-relative helicity should be supportive of a few supercells. Not the most backed surface flow, but this could change...
 
It seems like every year, or maybe every spring and fall, this discussion comes up regarding moisture return and low LCLs. But things haven't changed and you don't need dewpoints in the middle 60s for tornadic supercells in the high terrain of the Texas Panhandle/Southwest Kansas. Current dewpoints are anywhere from 60 to 51 and dewpoints in the upper 50s will probably be the case on Wednesday. With moisture pooling you may even get some scattered low 60s. That's fine.

I checked out the Del Rio Sounding as well as the Corpus sounding. Del Rio has a 850mb dewpoint of 12C. That should take the "long way" up the high plains toward the Texas Panhandle as the shortwave approaches, and I don't think the NAM is being too overly aggressive forecasting between 10 and 12C 850mb dewpoints.

Clearly the richest Gulf moisture is quite shallow. But the moisture appears sufficient to support a few tornadic supercells Wednesday. I do agree with the SPC in saying the greatest threat will be large hail, but I do believe there will also be a notable tornado threat, or at least a greater threat than is being indicated by anyone on this thread.

Without a doubt I would be out there chasing if I could.
 
I generally agree with Jim. The forecast dewpoints are fine for a high-based storm. Note the air temps are concurrently forecast in the low 80's, so a 20 degree spread is not unreasonable. I am concerned though with the shallow nature of the moisture. With moisture pooling the only real source, as the cap erodes deep mixing could also erode the modest moisture in place, and the low level RH is already going to be sufficiently low that storms will tend to quickly become outflow dominated, and with such weak surface flow forecast, this I think will prevent an otherwise favorable setup from producing many tornadoes, as the model forecast from the NAM currently stands. Indications of a dryline surge combined with a double warm front structure leading the surface low certainly looks like a setup worth looking into tomorrow morning for those with easy access to it. An obstacle not well shown in the model forecast is that mid to high level clouds are almost a certainty, and with the low sun angle this time of year that could be problematic for adequate insolation to get storms to develop away from the strongest forcing.

Glen
 
I for one am extremely excited about tomorrow’s potential regardless of moisture problem if there is one. I think anywhere along the DL just east of the W OK/TX state line will be prime for this chase. That also depends on if there will be any higher concentrated moisture pools. Most of the upper air speed and directional shear will be south of the SL. In the morning and through out the day I will be looking for enhanced moisture pools and backed surface winds along the DL. I am hesitant to play the stationary front due to possible cloud cover.

Like I said this setup is really get me excited. As long as everything goes to plan and I don't screw up I just may get my Oct tornado and a great way to end the 2005 chase year.

Mick
 
I am glad to see the ETA/NAM coming more in line with the GFS position of the low tomorrow. I'm cautiously optimistic for tomorrow, but enough so to warrent the trip from Denver. I'll be on the road for Garden City, Kansas tonight where I'll stay overnight and kick off from tomorrow.

The higher terrain eases my concerns on moisture a bit, but I still remain skeptical if enough can pool in the area to help keep the bases low enough to maintain decent tornado chances. Wind shear looks pretty good over the area and I absolutely LOVE the SFC low position and hope it verifies. Get some of the richer moisture in the area and I'll really be happy.

My target for tomorrow is likely going to be in the Central Oklahoma Panhandle to the extreme Northern Texas Panhandle. I will be playing the low and close to the front unless there is a problem with cloud cover, in which case, I'll drop further south along the dryline.

Stay tuned...
 
Well I'm not excited or un-excited. I'm not sure what I am, other than ready for some fashion of a chase before winter kicks in here. If nothing else there should be some fall photo ops along the way(back).

I'm considering leaving tonight for somewhere in northern KS and making the rest of the trip tomorrow. I know if I stay home all night and try to get up super early it won't be sounding like such a great idea when I get up.

I've seen enough events with forecasted weak low-level flow change the day off to be fairly excited...or maybe more optimistic...on this one. With that said I agree with Glen and do not like that sfc flow. I'm also not sure I like how the ne winds are north of the warmfront. It seems too close to the boundary to be blowing so strong out of the ne. Makes me question how worthwhile that boundary will be(dont want that thing sagging south all day). But at the same time is will be the only real source for moisture pooling and more backed flow, but more importantly something for a storm to anchor on or interact with. I will be close to it so long as it isn't dropping south. If it drops south I will begin to have flashbacks from the April 20, 2002 trip to just north of Lubbock(boy did that one op, long drive chase suck).

I love the shear, and especially so if the sfc flow is stronger. It seems like it is worth the chance so as of now I'm game. Early target of PYX(whatever that is...Perryton I guess) in the TX panhandle to a location due south of DDC on the KS/OK border. That will be my target as something goes up further east on the WF and waves bye bye to me. Leaving this evening......I think....
 
Looking at todays, there is what looks like to be an upper level cyclone, with a lot of moisture embedded....look what it's causing right now, near the four corners...a tornado warning and all. It looks like the dryline might stall abruptly along the OK/MO border. The biggest threat I see, would be damaging winds, hail, and potentially heavy rain-fall...not so much for tornadoes though. There will be supercells (Almost positive) due to the deep layer hodographs. SFC heating should be in the upper 80's leading to MLCAPES of 2500 J/KG (not bad). My guess is the storms will be non-SFC based, and elevated. I'd really try targetting Childress.....
 
Target is Buffalo, OK: this setup is too good to pass up being so close to Norman (3.5 hour drive). The forcing will easily overcome the cap by early evening and the shear will be great for supercells with large hail and hopefully some incredible structure. Tornadoes are highly possible as well. Biggist worry would be the possibility of high to mid-level cloud cover associated with the shortwave early in the day, which would cut down on sfc heating, which would lower the CAPE values significantly.
 
The cool side of the front remains relatively moist, so storms along the boundary that move just north of east should move into lower dewpoint depressions and high 1k SRH values. This could make for a junkfest but with a tornado or two perhaps, not entirely uncommon with off-season south plains systems.

I expect the storms further south along the dryline will be more isolated, but without the boundary they'll have much less chance to produce a tornado. They could still be photogenic given the ~40 knot deep layer shear values down there.

The list of worries is a mile long: moisture depth, cloud cover, sun angle, ec. But this is probably the last best chance for supercells and tornadoes in 2005, at least down here in the southern plains. And on some level, with ~ 2000 j/kg, modest low level shear, and a boundary in the neighborhood, there's almost always some chance for tornadoes. The fact that we can see how storms might move into a more supportive RH environment makes the possibility even more compelling.

I like Canadian to Spearman to Guymon to Woodward.
 
For those looking for something else to ponder on this event, the WRF run from 00Z last night was pretty interesting in terms of evolution. Seems to be pretty close to Edwards outlook in some ways, so he may have liked that solution in particular. An additional common feature between last night's WRF and the morning ETA is the building of the surface theta_e ridge back along the OK panhandle toward extreme SE CO, with a secondary low. Accompanied by an axis of high low-level shear, it will be worth watching to see if the secondary low is potent enough to draw a decent tongue of moisture back that far, as that could yield some notable storms back into the OK panhandle region. As Edwards mentioned, certainly risk of very early storm initiation - which has its advantages and disadvantages. Much too far away for me to be more than casually interested, so I'll be watching it play out virtually. Again.

Glen
 
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