12/26/08 FCST: OK, KS, MO, IA, TX

[Scott Weberpal]

Deep low in E. KS, excellent moisture return for a winter chase, strong kinematic profile...what more could you want in Dcember?

Looks like some chasers could have a Merry Christmas on the 26th!

 

[Brandon Ivey]

A system to keep an eye on! Right now it looks like eastern Oklahoma, Northwest Arkansas, into Missouri would be a general target area. Warm temperatures and decent moisture return appear likely over this region. Good shear will be in place as well!

 

[Michael O'Keeffe]

I have been eyeing the Texas area fro this system mainly because we are heading down there on the 26th. The 12z NAM is looking pretty pathetic with CAPE barely reaching 500 j/kg over a small area of NE Texas, but it is showing a nice dryline located near the Dallas area with 60F tds extending all the way to the dryline. It is also lacking any precip except for some stuff up in OK and AR along the cold front. The 850s don't even look that bad on the NAM it is mainly the CAPE that is concerning.

The 12z GFS is a different story. It is much more enticing with a nice dryline in Texas as well, but with about 750+ j/kg of CAPE at 00z with a rapid increase of 1250+ j/kg of cape along I35 at 06z. It also appears a new low with develop during the day Friday causing the moisture and dryline to retreat westward after dark (Greensburg). In addition shear should be pretty wild as is always the case in winter, but those moderate CAPE values are looking very interesting. With the SE surface winds and unseasonably warm temps I'd say we could see some nice supercells or at least severe weather over much of N/C Texas Friday night with a likely hood for tornadoes.

For those who are wondering where I got this info since Nexlab is down here is the link. http://hoot.metr.ou.edu/models/gfs/wind/850mb

 

[Bob Hartig]

COD is back up and running, at least for now. I'm starting to feel good about the prospects for us northerners. Besides deep moisture and 60s temps, GFS also shows a dash of mixed layer CAPE overspreading much of the region as far north as SE Iowa. I'm presently contemplating St. Louis south through the bootheel.

 

[Chris Lott]

This has started to get my attention somewhat. Like Michael said, the models appear to shoot a tongue of 1250-1500 CAPE up the I-35 corridor in Texas and east of that. I'm just not sure the upper level energy will come far enough south to trigger anything. However it does appear to be something to watch. I believe enough moisture will be in place, since it won't take much this time of year. The only other thing I don't like about this setup is if anything does materialize it probably won't be until after dark. But this time of year I will take what I can get. I will be model watching the next couple of days, and not the runway models.

 

[Bob Hartig]

I've given up on this one. I'd hoped Friday's setup might nudge just a bit more north and east, but that ain't gonna happen, and it's not practical for me to drive to western Missouri/Arkansas hill country to chase a linear system ripping along at space shuttle speeds. With directional shear confined mainly to the sfc-850 mb layer in a low-CAPE environment, any tornadoes that do occur will be brief, unpredictable spinups. Could be a different story in Texas, where there's some actual CAPE to work with, but that's well out of my range for such a marginal setup.

My buddy and I are still considering Saturday late morning/early afternoon in southern Indiana. The scenario doesn't change, but it's closer to home.

Best wishes to those of you who do venture out.

 

[Brandon Ivey]

Any severe threat on the 26th appears to be an overnight event that will extend into the 27th. The latest model run with the WRF and GFS have slowed this system down a little. The WRF more than the GFS, but trends are indicating that Eastern Kansas and more of Eastern Oklahoma could be included in this threat.

I have noticed a lot of complaints about cape values. The overall cape looks to struggle to reach 1,000j/k, but take a look at the 0-3km cape values. They actually increase overnight building to over 150j/k by midnight. That is enough to make me happy this time of year!

The WRF currently places this instability axis along and just east of I-35 in SC KS and Northern Oklahoma, while the GFS places the axis over Southwest Missouri. Take a look at this link below. It shows instability increasing overnight at Springfield, MO, similar to what the models are doing with this system. I documented a tornado around 1AM in far SE KS during this event.

http://weather.uwyo.edu/cgi-bin/sou...AR=2002&MONTH=12&FROM=1712&TO=1812&STNM=72440

The BIG negative is the unidirectional (speed shear) over the warm sector. I could only find 45 degrees of turning, at best, between the SFC and 850mb. It would be nice to see more directional shear however, the models still show impressive 0-1km SRH values between 300-400m/s.

I hope models continue to slow this system down a tad. The WRF shows a target close to home right now. I am in need of a good chase, even if it does occur at night. I was really dreading the notion of chasing at night in the hills of Western Arkansas, but that could still be the outcome.

 

[Chad Cowan]

I have noticed a lot of complaints about cape values. The overall cape looks to struggle to reach 1,000j/k, but take a look at the 0-3km cape values. They actually increase overnight building to over 150j/k by midnight. That is enough to make me happy this time of year!

My thoughts exactly. Low-level buoyancy is key for these off season events and there will be more than enough 0-3km CAPE throughout the warm sector for some low topped supercells if storm mode can remain discrete. I've been digging through my bookmarks for another great writeup by John Davies about 0-3km CAPE but can't find it right now. Biggest concern will be horribly veered H850's... I will be keeping a close eye on sfc wind vectors looking for locally backed areas and/or subtle boundaries. I'm not looking to head into the hills of Arkansas so I'll probably target the Pittsburgh, KS area southward.

 

[Michael O'Keeffe]

Hey Chad,
Here is the link to Jon Davie's paper on low level CAPE associated with tornadic supercells.

http://www.jondavies.net/LLthermo.PDF

I agree with Brandon and Chad as well. That low level CAPE in Kansas is interesting to say the least however I will be down in Texas on the 26th and am hoping something severe can get going down there. It appears 0-3km CAPE will be about 100-150 j/kg which is OK but not anything significant. SBCAPE may reach close to 1000 j/kg which I think with the insane helicities may be enough to get something going. I have been researching some notable winter events such as Dec 29, 2006 and Jan 7, 2008 and I noticed little to no SBCAPE was present, but helicity was very potent with over 500 m2/s2 during the Jan 7 outbreak! and >350 m2/s2 during the Dec 29, 2006 event I would like to see more of a north/south boundary and it appears a dryline is present from far S Oklahoma into Texas before being overrun by the cold front sometime late Friday night. I am hoping that the dryline with the SSE winds may be able to create some convergence and possibly initiate some storms (maybe supercells with insane helicity) before the cold front comes plowing through. Either that or a tail-end charlie which is possible as well.

 

[Erik Burns]

I think this system looks just ok for this time of year.. The best area I see is along I35 in NC Texas.. Dryline moves forward and develops a nice sharp gradient to it. Moisture will not be a problem in the area. CAPE who cares it will be there, just not a lot of it. The amount of helicity and shear will make up for the lack of CAPE. The Whole set-up screams Linear mess. The Unidirectional winds aren't going to get any storms spinning. Things can still change though and always get better or worse. If storms do fire along the DL it will be after dark and will be a short lived event since the Cold front will probably take everything over. But for December I will take it.. Better then nothing. If It had more directional turning in the lowest section of the atmosphere I would feel better about it. We will see how the next few runs look.


( Mods please Add Texas to the title )

 

[Dick McGowan]

http://wxcaster4.com/nam/CONUS_ETA_0-3KM_CAPE_66HR.gif
All I need to look at for instability.

Night chasing in the Flint Hills it is!

 

[Robert Rohloff]

Looks like the system has slowed down at this time. It also looks like Eastern Oklahoma could see a extended threat due to the speed. Most definitely a night stalkers event shaping up. I chased the event 1-7-08, it was a night chase in the hills, if I never mentioned it I hate chasing the hills............I will still be out there however.

 

[Steve Polley]

The fly in the ointment that I see right now is how much available moisture the system will have to work with. As of this morning, 60 dews were still near the coastline of Texas. The GFS and the NAM are both agreeing that the 60 dews will make it as far north as Southern MO. Time will tell. Also, for once the GFS is having this system slower and further west than the NAM. Hopefully surface obs will show the beginning of the moisture return by tonight.

 

[Brandon Ivey]

I don't think moisture will be an issue. Dewpoints up to 70 have made it inland over Texas as of 4pm. We are still ~30hrs out from this event. The best parameters come together around 3am from the forecast soundings I have looked at. The prime time for this event should be from midnight to 6am on Saturday. Right now I plan to target Parsons, KS. I think the terrain and road networks are best in that area out of the whole risk area. Anyone know of some decent areas elsewhere? I think far Northeast Oklahoma and far Southwest Missouri can be okay at times. I just haven't chased much in that area.

 

[Chris Lott]

This setup still looks good to me as well, even though it will definitely be a late event(probably after midnight.) The moisture is pumping in as we speak, as we are almost at a 57td in Waco, so the 60 td's won't be a problem tomorrow. I'm concerned with the cloud cover tomorrow limiting instability. The models still show that nice tongue of CAPE up the I-35 corridor through N. Texas into early saturday morning ahead of the upper level system. I really don't like chasing at night but tomorrow I just might have to go for this one. I'm still liking N. TX into SE OK for the best shot at some discrete cells. I believe it all turns into a linear mess as it moves east into Arkansas and Missouri.