10/19/05 FCST: Plains

[Rocky Rascovich]

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]

 

[Angie Norris]

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

 

[Brett Adair]

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.

 

[Angie Norris]

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

 

[Fred Gossage]

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.

 

[Fred Gossage]

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.

 

[Fred Gossage]

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......

 

[Rob Satkus]

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

 

[Karen Politte]

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

 

[Mickey Ptak]

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

 

[Kiel Ortega]

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.

 

[nickgrillo]

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.

 

[Mickey Ptak]

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

 

[Andrew Khan]

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.

 

[BrandonWhittington]

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.