12/6/04 FCST: Mississippi valley/OK/TX

[Dan Cook]

Noticed the slight for day 3, but noticed the wording at the end:

POTENTIAL FOR SIGNIFICANT SEVERE WEATHER MAY EXIST IN PORTIONS OF
THE SLIGHT RISK AREA.

I'm looking through the HWOs but am not finding much other than flooding problems.

 

[Andrea Griffa]

Shear looks like interesting from eta forecast with good values of storm relative helicity. A good short wave trough associated with interesting temperatures at mid level (overall in Texas) might sustain a good convection. Moreover the presence of good moisture in the low levels might mantain some interseting updrafts.

http://weather.cod.edu/forecast/ETA/etaUS_..._3km_hel_60.gif

 

[Robert Dewey]

Don't rely too heavily on the ETA... Almost ALL of the other models are showing a further southeast solutions, much like the GFS, though a bit stronger. Then again, the ETA did the best on the last synoptic event when models had trouble.

 

[Dan Cook]

Jackson's mentioning a possible outbreak on Mon.

 

[Andrea Griffa]

Originally posted by Dan Cook
Jackson's mentioning a possible outbreak on Mon.

Moreover instability and shear looks like improving :wink:

http://weather.cod.edu/forecast/ETA/etaUS_...0_mlcape_36.gif

 

[Caleb Witt-Schulte]

Springfield, MO is mentioning a possible chance of tornadoes on Monday in their hazardous weather outlook.

 

[Rod Neff]

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THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ON MONDAY AFTERNOON
AND MONDAY NIGHT AS A LOW PRESSURE SYSTEM AND TRAILING COLD FRONT
MOVE THROUGH THE REGION. THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG
AND AHEAD OF A COLD FRONT MOVING EASTWARD THROUGH THE AREA. A FEW
STORMS MAY BE CAPABLE OF PRODUCING DAMAGING WINDS AND LARGE HAIL.

It's looking better. But I dont think there would be any sun for monday. Crap!!

 

[Shane Adams]

Could someone amend this date's topic to include the Southern Plains states of OK/TX? Seems a real possibility of a decent chase tomorrow from NW TX through the RR Valley area. Moderate CAPE with insane helicity looks like a recipe for love somewhere tomorrow.

 

[Shane Adams]

Thanks.

Tomorrow looks interesting from southwest of SPS through SC Oklahoma. Moderate CAPE but incredible helicities through 1-3km. I know this is fluctuative because you can't really forecast helicity, but it looks very interesting for a surprise storm or two. Wichita Falls would be my target as of now. Tomorrow looks like a sleeper type day, that might catch alot of folks off-guard.

 

[Dan Hawblitzel]

One significant difference between tomorrow's event and the event of 11/23 looks to be the cloud cover. WV loops shows a very large area of moisture and clouds streaming in off the Pacific....and KHGX discussion mentions that this plume extends all the way back past Hawaii? At this time on 11/ 22 a nice midlevel dry punch was evident coming in from NM and west TX. This probably doesn't bode well for areas south of I-20 where upper dynamic forcing will be weaker so more is riding on instability. Although it is hard to ignore the ETA forecast soundings showing CAPE values over 3000 across central and southeast Texas tomorrow, with 1000 all the way up to the Red River...despite forecast surface temps in the upper 60s/lower 70s and dewpoints near 65. Given the current (23Z) sfc observervation of 75/71 at KHOU and the 60F dewpoint contour already as far north as Temple to Texarkana, this forecast does not sound unreasonable.

I'd probably focus on areas within a Waco -> Brownwood -> Wichita Falls -> Paris -> Waco "box" but that is quite preliminary given the uncertainty of timing and destabalization.

 

[Scott Olson]

Tommorow certainly does certainly hold the possibility of being significant. However, I think the instability is overdone and that you cannot count on much heating. However, I think the more reasonable spot for convection/intensification will be in central texas. Based on current anaylsis I'd hedge my bets on the Madisonville, TX area. Dynamics are definately strong/severe thunderstorms. I would go for the area of right rear quad during the 19z-21z timeframe. Still most of this area is Hill Country and these storms will be on the move.

 

[Alex Lamers]

Things certainly do look interesting, particularly in Eastern Texas where many factors will be phasing together for an interesting day of weather activity, or shall I say night? Looks like best window for severe weather will be 23Z-07Z across the Arklatex. I can see what HGX was talking about with the stream of clouds. WV Loops show it nicely. Takes the LLJ awhile to kick in, ETA shows it really establishing its presence on the 00z panels. I think that as this shortwave becomes negatively tilted and the surface low deepens, this whole setup will only become more dynamic. Certainly a setup for rotating storms. Question would be degree of instability at this point as others said. I think you will get some 800-1200 j/kg max thetae CAPE values nosing up as far north as into S AR/SE OK with the highest degree of instability located across Eastern Texas. Things should get revved up late afternoon/early evening across Eastern Texas.

 

[Andrea Griffa]

Originally posted by Alex Lamers
Things certainly do look interesting, particularly in Eastern Texas where many factors will be phasing together for an interesting day of weather activity, or shall I say night? Looks like best window for severe weather will be 23Z-07Z across the Arklatex. I can see what HGX was talking about with the stream of clouds. WV Loops show it nicely. Takes the LLJ awhile to kick in, ETA shows it really establishing its presence on the 00z panels. I think that as this shortwave becomes negatively tilted and the surface low deepens, this whole setup will only become more dynamic. Certainly a setup for rotating storms. Question would be degree of instability at this point as others said. I think you will get some 800-1200 j/kg max thetae CAPE values nosing up as far north as into S AR/SE OK with the highest degree of instability located across Eastern Texas. Things should get revved up late afternoon/early evening across Eastern Texas.

Seeing convective forecast, central and central estern Texas zone looks like the most favorite for a good convective development: south Texas will be inhibited by a great presence of CIN. Corpus Christi's inversion is quite strong and we have 265 J/Kg of CIN...Without the sun is very difficoult to destroy.

http://weather.uwyo.edu/upperair/images/20...72251.skewt.gif

Same thing for Bronswille: 302 J/Kg of CIN

In the meanwhile SPC's update is for a moderate risk for estern Texas, LA,AR,Misissipi, western TN.

 

[Kevin Scharfenberg]

Today appears to be characterized by:

1. Strong deep-layer speed shear over the whole region.

2. Very strong speed and directional shear in the lowest 1-2 km over much of eastern Oklahoma, western Arkansas, far NE Texas and far NW Louisiana.

3. Lots and lots of clouds everywhere.

4. Limited instability and a weak capping inversion everywhere.

Usually significant/long-lasting tornadoes are difficult to come by on a day like today unless you can get some pockets of instability in the right place at the right time. I would definitely be watching the Arklatex region to see if the near-70 dewpoints can get up there, with a couple of hours worth of sun, to sufficiently destabilize the atmosphere before all the forcing arrives in the afternoon. Storms should light up along the I-35 corridor in Texas by early afternoon and it won't take long to see whether a supercell or squall line mode will be favored.

Farther northwest, closer to central Oklahoma, the atmosphere looks too cool and stable, and the forcing too strong, to allow for anything other than widespread ordinary convection.

 

[Jim Bishop]

The strong inversion near the 800/850mb level has prevailed, just look a the For Worth 1800 UTC sounding. Yikes! Thus, it appears unlikely descrete cells will form ahead of the squall line. Interestingly enough a dry slight has snuck in over the past 2-3 hours and eroded the upper level clouds ahead of the line between Abilene and Dallas/Fort Worth.

Nevertheless, it looks like the strong capping inversion will be the factor today keeping descrete supercells from developing. Damn cap!

Still can't rule out a couple tornadoes within embedded mesos within the line.