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10/19/05 FCST: Plains

For the past several runs, this upcoming system progged by the GFS and
Euro may get us out of this comatose mode we've fallen into...maybe.
Both of these models has a fairly stout cyclone coming out into the
central plains by Wednesday morning 10/19. the GFS has been trending a bit
slower and will be interesting if this comes out as an open wave or closes
off over the four corners area.

Regardless, a pretty good chance of severe weather is likely from ICT
northward to DSM and on east toward CGX for Thursday and Friday...if the
models verify. Down here in Okla., precip. is next to none based on these
models...I think the threat of severe weather here in the OKC is a
possibility if the low tracks further south and moisture return is
evident.
Temps prior to this should be above normal as well as the dewpoints. Add
to this projected shear profiles into the brew..I think a chase may be in
order if this materializes on Wednesday for any points south of EMP for
me.
If its later, too many committments will preclude me from going out.
I'll be watching this close.[/b]
 
I'm thinking central/eastern KS for a starting point on this one, also (ICT for a starting point). This morning's GFS has the low tracking a bit too north for OK to partake of the action. Looks like there is a bit of a moisture plume up into eastern OK, but I'm thinking its out of synch with the dryline. Also looks to me like the dryline meets up with the cold front sometime overnight. Shear does look good, with that nice little jetstreak coming in.
The main thing that worries me...it gets dark too freaking early!!!! I'd hope if anything fires, it does it late afternoon-ish. I've got a feeling that a good bit of the action is going to be of the after-dark variety.
If Wednesday is the day, I'm out of class at 1:30 (and off that afternoon), so a quick trip to KS isn't out of the question...if it slows down to be Thursday, it's a no-go (not out of class until 3:45 or so). Getting in some field observations for my met class would be soooo sweet!
Angie
 
ICT has always been a good starting point for me. Harper/Sumner Counties for certain nearing Medicine Lodge, KS if there is an evident dryline situation. The roads are wonderful.
 
Latest GFS has moved the trough axis a bit SE on the 500mb putting OK at the base of a sweetly negatively tilted trough on Wednesday. Nice jet max at about 50kts, still good shear, however....looks like it mostly comes through after dark...figures.
Any other thoughts out there?
Angie
 
Well this morning's 12Z run of the NAM starts to bring the system's progression into the Plains into focus........

One thing I REALLY DON'T want to see....

http://www.weather.cod.edu/forecast/ETA/et...850_dewp_84.gif

850-mb dewpoints are around 11-12C over the area....but look back over the Gulf and TX at the very dry boundary layer air mass! If this is correct, low-level moisture may be a real problem.

Even more concerning still are the surface dewpoints...

http://www.weather.cod.edu/forecast/ETA/et...S_2_dewp_84.gif

BIG hole of <50F sfc Tds over much of TX...... that combined with all the dry air at 850-mb leads me to believe that WHAT MOISTURE THERE IS just ahead of the sfc low and dry line will be really shallow.
 
I think there may actually be an okay tornado threat........but not where you would initially want to expect....

Look at northern Kansas......

850-mb moisture seems to be pooling here along what appears to be a likely warm front...with almost 13 C 850-mb Tds evident.... that's decent moisture... http://weather.cod.edu/forecast/ETA/etaUS_...850_dewp_84.gif

Surface moisture also pools here with dewpoints well into the 60s over northeast KS http://weather.cod.edu/forecast/ETA/etaUS_...S_2_dewp_84.gif

Area is northeast of the 1002-mb sfc low over swrn KS http://weather.cod.edu/forecast/ETA/etaUS_...S_0_prec_84.gif ....which would lead to good low-level shear.... http://weather.cod.edu/forecast/ETA/etaUS_..._3km_hel_84.gif and http://weather.cod.edu/forecast/ETA/etaUS_..._1km_hel_84.gif

Because of the low-level moisture pooling, coupled with 500-mb temps pretty cool for this time of year in the Plains http://weather.cod.edu/forecast/ETA/etaUS_...500_temp_84.gif , decent instability develops with LIs of -4 to -6 http://weather.cod.edu/forecast/ETA/etaUS_...S_2_dewp_84.gif and MLCAPE in excess of 1500 j/kg http://weather.cod.edu/forecast/ETA/etaUS_...0_mlcape_84.gif (SBCAPE is even higher)

This combined with the potent shortwave ejecting out into western KS (which NAM, GFS, and ECMWF agree upon) http://weather.cod.edu/forecast/ETA/etaUS_...00_avort_84.gif , allowing for a 50 kt H5 SW jet streak http://weather.cod.edu/forecast/ETA/etaUS_..._500_spd_84.gif to couple with a 30-35 kt H85 SSW to Sly jet streak http://weather.cod.edu/forecast/ETA/etaUS_..._500_spd_84.gif ...with the 850-mb winds turning more easterly over northern KS..............

I wouldn't be surprised to see some supercells with a few tornadoes over northern and especially northeastern KS during the early-to-mid evening hours.
 
I think that if anything goes there, based on the 12Z NAM, it would be AFTER 00Z..... which is also gonna mean there's gonna be a race against nocturnal boundary layer decoupling......
 
After perusing latest model data, Beaver county Ok would be my target....but with this type of system, that could change a lot over the next 2 days as better upper air sampling is established. Really don't see much reason for any drastic changes tho at this point. Moisture/instability still in question, but I am thinking there may be an isolated tornado or two near the low especially if ETA verifies with it's low 60 dews. Could be some photogenic high based s'cells with big hail along the dryline through eastern Tx panhandle. At this point, I would be happy with anything that would get me a few nice pics.

Rob
 
Hmmmm......the ETA and its dryholes. Any ideas?

I would be getting more excited about spending gas to chase this upcoming system if the ETA wasn't absolutely insistant upon working in a big old dryhole from San Antonio all the way up to sern OK by the target timeframe of 0Z Thursday 20th. No precip accounts for this dryhole, and our southerly fetch is connected at least to the Gulf by then.

What worries me is that I don't want to get caught out by another ETA bungle - and stick in OUN at home while tubes drop in wrn OK. I'm not sure I'll ever forgive the ETA after what it did to us this past spring......or ever fully trust it. What rings alarm bells with me right now is that it does not appear to be handling Wilma very well. I may stick with the GFS solution until I can look at the RUC on the day of.

By 0Z Thurs there is a fairly funny-looking, thin finger of 60+ Tds working their way towards the low from the northeast - which seems a bit screwy to me. If it were to verify with 65+ Tds in nwrn OK by then - than I'd sure take it. But I don't buy it at all.

I'll just wait and watch for now - and see if the ETA can convince the atmosphere to produce yet another fabled dryhole. I seem to remember it's very persuasive.......

KR
 
Man what a nasty NAM run. This mornings NAM indicates a much faster advancing CF due to the surface low much further to the south into the Childress area. however the Low is not as stacked as it was forecasted to be in previous runs. If this run proves true then most of the supercell (if any) potential will be between LLB and CDS starting around 21Z. However, the GFS is still forecasting the Surface Low to be SW KS and NW OK. In which I am hoping this will continue to be the case.

It’s hard to tell which model has a better handle on this forecast. Considering the GFS has been somewhat consistent with the upper air patterns I would hope the see more inline forecast between NAM and GFS.

Mick
 
Given the current situation, BL moisture is going to be a SERIOUS problem for Wed. Current soundings along the Gulf Coast don't give me too much hope for good moisture making it's way back to OK in time for this storm. The current weak and somewhat northerly flow on TX soundings really concerns me...in a good situation most of today would be spent spinning the winds around to the south. However, the ridge present over Southern Texas (and the current RUC loop of 850mb winds) doesn't give me much hope for any true Gulf-to-Oklahoma moisture flow. I don't disagree with the current SPC outlook with large hail as the primary threat. I just don't think the moisture will be there for nice LCLs for tornadoes.
 
I've only briefly looked at the prospects for the TX/OK panhandles, and it looks "okay", even per the latest NAM. The dryline is much further south, according to the NAM, and is roughly located from about Clarendon to south of San Angelo. The GFS is more progressive with the eastern propagation of the dryline, with it being located over eastern TX/OK panhandles by 0z Thursday. The best low-level shear should be located north of the cold front, which is located over the TX panhandle, and then curving northeast into the Ozarks (per the NAM). The 12z NAM AND GFS is showing low-60s Tds across most of the panhandle, which when combined with temperatures in the low 80s, yields nearly "doable" LCLs (<1200m~). Instability is in the moderate range for most of the area (1500-2500 j/kg SBCAPE). Boundary layer moisture is fairly decent for mid-October, with a fairly deep moist layer pretty evident across the eastern panhandles. This, in addition to the instability/wind fields (just wish 850mb flow was a little stronger) should be enough for supercell structures, mainly capable of large hail... And, perhaps, a few tornadoes near the surface low, wherever it finally lands at.
 
18Z NAM just came out and, yet again, it’s playing with my emotions. This run keeps the SL in SE TX Panhandle as did the 12Z run. However, Td’s at the surface and 850 mb continue to steadily rising due to god knows what. I am not sure how it is getting these numbers but hopefully it is right. Naturally with the Td’s up so is the instability so forecasted CAPE 1500 – 2000 along the front and most of the shallow dryline. Per this run I also gather that the action might start real close the SL and move along the stationary front NE into SW/W OK. The largest Helicity values are north of the front but I will take that with a grain of salt because speed and directional shear is not going to be our problem come Wed. The bottom line is moisture or the lack there of.

Mick
 
Wow, things have REALLY changed a lot, in the latest day...I was originally going to target North Platte, NE or Kensington, NE, but the activity looks like it will be pushing south-bound, extremely, tonight/tommorow.

I would say a good target area NOW, per the latest GFS run, would be Childress or Borger, TX...maybe even a little farther north towards Atlus/Lawton, OK.

There are SFC Dewpoints in the upper 50's, with ascending Mid-Level Lapse Rates, should make for some pretty moderate MLCAPE...nothing extremely high. There should be a nice amount of shear due to a mid level jet, across the portion of the region. That being said, there looks like a GOOD chance (For now) of a supercell...and possible tornado.
 
I really don't feel that moisture return will be a big problem on Wed. Current observations show that the moisture flowing into the southern and eastern panhandles. Dewpoints are already in the lower 60s in Southwest Oklahoma. Right now, my current thinking is that the surface low will form around the north-central TX panhandle and track east. Right now, Perryton, TX is looking like a really good target area, and if this is the case, I will just stay around the house here in Booker, TX. I just would like to see the moisture return be a little better.
 
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.....
 
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