10/11/08 FCST: KS/OK/TX

[Andrew Stoller]

12Z NAM is out and has eleminated all CAPE at OZ across western KS. Looks like the chase is off for me. What a let down....

There still may be some hope - LAHX is showing 800 + J/KG at 00z Sun. But the hodograph isn't as pretty as Garden City.

http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=036&STATIONID=KGCK

What a shame that has to get killed by no instability/cloud cover and crapvection.

 

[Michael O'Keeffe]

The 12z WRF model shows a significant cap over much of the interest region through 18z Saturday so how is it possible for precipitation to be on the showing up at 18z Saturday as well. I think I will trust the CINH model over the precip model. Even with 800-1000 j/kg, the extreme shear and high elevation of the region we could easily see supercells and tornadoes as well. Almost every chase I have gone on we usually see more CAPE than forecast anyway, so I am still a go for tomorrow. With hodographs and a system like this it could easily be worth it.

 

[Verne Carlson]

Have to see in the morning how much Norbert's cirrus shield has been pulled into e NM and w TX and how it will start to affect the panhandles.

http://www.nrlmry.navy.mil/sat-bin/...s11.vis.x.pac_southwest.x.jpg&MOSAIC_SCALE=15

It will take every minute of daylight insolation to overcome the warm upper levels. I think I'll wait till the morning and then make my decision on go or no go.

Edit: Latest SPC day 2 expands the slight risk area and breathes a little life back into the forecast as well with the 'T' word again!

 

[Brian Stertz]

I was looking at the 18z MesoEta and it has most of the strongest lift from the NW Texas Panhandle into NE New Mexico and SE Colorado. The better instability looks like it will favor the western sections of the TX Panhandle and Caprock area and possibly even into E.New Mexico. This one looks a bit too risky to bite on and a little disjointed. I've got a football game to watch anyways so no biggie.

 

[Adam Penney]

Well I have to say, as of right now, I am very glad I decided not to head out the door and chase tomorrow. The new 00Z NAM is out and has dropped dewpoints even a little further. Also the best dynamics along with greater helicity values dont kick until ~0Z, which by that point, most of the instability(whatever little there is) is gone. This still could be a case of high risk/high reward, but I have very little experience with low instability/high shear days, so I will sit this one out and see if I can learn a bit.

Good luck to all that take the chance!

 

[Shane Adams]

Fall systems need to be sure things a few days out. The problem is always thermodynamics. It's quite easy to get good shear in place, but that alone is worthless. I'd much rather tackle a low-shear setup with amazing instability than watch all my towers getting sheared over and ripped to shreads by an insane speed max with little or no instability to support it (like what will happen tomorrow).

I look back on all the Fall systems I've chased, and all the decent ones I knew I was chasing before the day of.

 

[Bill Schintler]

Chase Target for Saturday, October 11

Chase target: Andrews, TX (32 miles north of Odessa).

Timing and storm mode:
An extensive area of mainly stratiform precipitation will be ongoing in the TX panhandle and into eastern NM during the early afternoon. This will expand east towards the target area between 3 and 4 PM CDT, while becoming surface-based. A few supercells will be likely east of the main precipitation shield.

Synopsis:
Changes are underway, with an amplifying H5 trough in the western US. Upstream 00Z soundings (MAF, AMA, EPZ, ABQ, FGZ, TUS, and MGYM) all indicate meager low-level moisture and poor lapse rates above 600mb. At the surface, dewpoints have been inching upward over the last 12 hours with southeasterly up sloping flow, and were pushing 60F over much of western TX. The WRF, GFS, and SREF have a good handle on surface moisture.

Discussion:
CI will overspread the TX panhandle from the southwest by late morning, limiting insolation. Instability will be limited, despite surface dewpoints in the low-60’s F with the help of large-scale up sloping flow, owing to modest mid-level lapse rates of 6C/km. The colder upper-level temperatures will remain well west of the area. MLCAPEs will struggle to reach 1000J/kg. Moisture at all levels will increase courtesy of Norbert. An area of SC will develop between a Midland to Lubbock line, and the TX/NM border, by early afternoon as a tongue of 15C-16C H85 dewpoints surges northward.

Both deep-layer and low-level directional shear will be sufficient for storm organization. A southerly LLJ will strengthen between late afternoon and early evening. In response to this, SFC-3km SRH will increase to 200m2/s2 late in the period. A modest tornado potential may exist with LCL’s in the 800 – 1000m AGL range. SPC significant tornado and supercell composite parameters of 0.5-1.0 are indicated.

- bill
11:00 PM CDT, 10/10/08