2/23/07 FCST: OK / TX / KS

Seems like there is not much talk about the prospect of a Friday "event before the event" kind of thing, but from the look of this morning's GFS and EC I think there are at least a couple of intriguing details to get excited about.

- Good, but not intense, midlevel flow should make storms easy to keep up with.
- Deep moisture axis ~50 miles downstream of the GFS' preferred initiation point, roughly from DFW to Bartlesville
- Modest SSEly flow and convergence along a well-defined dryline
- Convective feedback on the 0Z images, along with moderate synoptic-scale ascent indicate a lower likelihood of a rapid squall line transition.

Saturday looks like a great event too, but I am afraid that if I were to go out I would be sorely disappointed by both terrain and storm morphology limitaitons. And either way, Friday is simply an easier chase for me to pull off since it looks like a very limited driving distance will be needed.
 
Seems like there is not much talk about the prospect of a Friday "event before the event" kind of thing, but from the look of this morning's GFS and EC I think there are at least a couple of intriguing details to get excited about.

- Good, but not intense, midlevel flow should make storms easy to keep up with.
- Deep moisture axis ~50 miles downstream of the GFS' preferred initiation point, roughly from DFW to Bartlesville
- Modest SSEly flow and convergence along a well-defined dryline
- Convective feedback on the 0Z images, along with moderate synoptic-scale ascent indicate a lower likelihood of a rapid squall line transition.

Saturday looks like a great event too, but I am afraid that if I were to go out I would be sorely disappointed by both terrain and storm morphology limitaitons. And either way, Friday is simply an easier chase for me to pull off since it looks like a very limited driving distance will be needed.

Friday, I agree, is certainly intriguing. The main problem though is the cap. It's going to be very difficult for surface based storms to form with 850mb temps 15C+. If they do form it would likely be ahead of the dryline over Western North Texas or Western Oklahoma . You'll likely need upper level support for initiation. That of course will be much further west at that time.

If initiation could be achieved then Friday looks like a more chaseable day than Saturday, both because storms would be moving much slower and the terrain is more chaser friendly.

Michael - I'm hoping for some magic on Friday too. Much rather have 2 chances to catch a tornado instead of just one.
 
Just a brief note... I moved the two posts above out of the 2/24 FCST thread since they pertain more to 2/23 than 2/24. In addition, I strongly agree that there is the possibility of a more chaser-friendly event Friday across the southern plains. I'll post more thoughts at a later time, but I'm more intrigued by Friday than I am by Saturday (though moisture return will be key Friday). FWIW, I chuckled at the "event before the event" statement, since Gabe Garfield and I were just talking about that as well...
 
Friday, I agree, is certainly intriguing. The main problem though is the cap. It's going to be very difficult for surface based storms to form with 850mb temps 15C+. If they do form it would likely be ahead of the dryline over Western North Texas or Western Oklahoma . You'll likely need upper level support for initiation. That of course will be much further west at that time.

If initiation could be achieved then Friday looks like a more chaseable day than Saturday, both because storms would be moving much slower and the terrain is more chaser friendly.

Michael - I'm hoping for some magic on Friday too. Much rather have 2 chances to catch a tornado instead of just one.
Yeah, this is why I loathe forecasting this far out. More subtle things like a small wave or something could make Friday the better day to chase due to better chase terrain as well as better storm motions, etc.

Either way, Saturday looks to be a screamer of an event storm wise. I sampled some logs in the target area and those storm speeds are bordering on the outrageous, espcially in that terrain. But you have the usual questions of cloud cover, available instability, convective debris and such that won't be resolved for several more days. I'm quietly hopeful we're set for an early start but I'm not gonna get my hopes up for a couple more days at least :)
 
Agreed on that being a real gut check forecast for Friday's event this far out. The main things that almost always happen on the "day before the big day" is that it seems like subsidence hangs tough until the sun goes down (or sometimes right before). I remember a few late Feb. events chasing in W.OK or N.Texas/TX Panhandle that it was right after the sun went down that things got very interesting and found myself chasing in the dark. Friday does appear interesting in some respects, but the upper support seems pretty distant during the daylight hours to get anything going of interest.
 
Its really hard to ignore the possibility of Severe Weather in North-east Texas and Oklahoma on Friday evening....If models are correct, we could see another setup, almost identical to the February 24, 2000 event, were tornadoes formed in the late evening and night time hours in Lipscomb County, TX. Stats and Radar loop of the event below....

http://www.spc.nssl.noaa.gov/exper/archive/events/000224/index.html

If the developing storm can slow down, and draw more moisture, we could possibly see tornado or two in western Oklahoma Friday evening. Everything else looks to be nocturnal after that.

Everything else looks to be on track for this weekend in Central Oklahoma as well. I-35 cooridor looks to be a hot spot Saturday afternoon.
 
The NAM/WRF goes through Friday now and it's very interesting. It shows a tongue of 55 dewpoints extending into Western Oklahoma to the Kansas border. Even more interesting is the -2 LI's and the narrow axis of 1000-2000 j/kg CAPE from Western North Texas into Western Oklahoma. By 00z it shows most of the CIN to be erroded, suggesting the potential for surfaced based convection along the dryline. If the NAM is correct with 55 dewpoints that far north on Friday, things may get interesting.
 
I'm not sure how much I buy into the 55F dewpoints this far north here in Okla. based on the WRF. SST's in the gulf have taken quite a hit with all the cold weather as of late.. we'll have to get one heck of a fetch of air from the southern GOM to get close to that, plus we'll have to see if we're not gunged out with stratus which will prevent dews from rising even further not to mention air temperatures which will hamper instabilities. Still what Jim eludes to needs to be closely monitored. Either way, with all the forcing going on as cyclogenesis takes place and it starts lifting out to the northeast.. things will surely get interesting.

Rocky&family
 
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The 12z WRF moisture return for 84 hours is attractive but seems pretty unrealistic to me, given current conditions, the moisture field evolution that the model itself depicts, and less-than-perfect low level trajectories off the GOM starting Thursday night. That's a lot of recovery for February. With the anticipated 850 temps (which DO seem more logical) and the upper level energy hanging back well west, this smells like a cap bust or a 3z initiation, but even then I can't see sufficient instability for deep convection remaining that long after sunset.

What I'm more curious about is how storms that develop late Friday night may or may not impact conditions for Saturday in Oklahoma or Kansas.
 
I think the most prudent thing to watch for out of Friday's setup would be - as Amos just said and as I was just thinking subcounsciously before getting to his post - the possibility of convection and/or storms firing on Friday night. While this may not provide much in the way of chaseable material for Friday chasers......it COULD possibly lay down some very interesting boundaries for the "big day's" storms to gobble up.

With this much dynamics crashing ashore and onto the Plains come Saturday morning - I will certainly be interested in any small little cooking OFBs hanging around I-40 in central AR, or further east or south for that matter, when forecasting for Saturday.

As for Friday - the day in question - I think that it'll be too little too late for initiation before dark. Also - the ETA's trajectories for moisture-return are really horrid now in comparison to what the GFS had been advertising. With our modified airmass coming from the Carolinas..........I don't know whether to believe any of the forecast Tds for Friday OR Saturday at this point.

KL
 
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I agree the latest NAM/WRF's depiction of 55 dewpoints seems a little farfetched. But to give it some credit the latest GFS supports just that.
Currently there are dewpoints in the low 60s over the Western Gulf. The question is how much does that moisture get mixed out as it gets advected to Del Rio and then northward to the Red River on Friday. Chances are againts the moisture making it that far north, but it's something to watch closely.
 
I may have to bite my tongue on my last post concerning the sst's. Check out this site with the latest SST's over the gulf. I'm rather intrigued by all the warm water north of the Yucatan Channel... Also, looking at the latest 12Z model from the GFS..isolated supercells may not be out of the question Friday eve. over western Okla. I suspect that they may be elevated, moisture and cap will be an issue, but Sat. looks like a gangbuster of a squall line to race across the state (Okla.) Below is the link to the sst's over the gulf.

http://fermi.jhuapl.edu/avhrr/gm/averages/07feb/gm_07feb20_0046_multi.png

Rocky&family
 
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12Z Nam this morning shows the upper level support arriving near 0z Sat along the dryline. This is essential to break the cap with mid-50s dewpoints east of the dryline (only minimal cape). That's 6pm local time which unfortunately means you have about a 30 minute window to see anything. There's very nice directional shear but I'd prefer this type of setup in May because of the longer timeframe for chasing. It might turn into a night chase if anyone's feeling adventurous. :cool:
 
I am personally more inclined (chance) chasing Friday than I am on Saturday mainly due to the storm speed. I can pass on chasing 50+ mph storm. Been there, done that and I can live without it.

I have much concern for Friday though. I think we could have supercells but I am inclined to add that they would be well after dark, 3-6Z+. Although we would have a decent amount of speed and directional shear prior to dawn, the main system is still well of to the west. Thus, unless heating and convergence ahead and along the dryline can suffice, the major lifting mechanisms just will not be there to give us the lift we need to brake the CAP.

Moisture, as mentioned by others, is and will be another player. For me, it’s not so much the concern of moisture advecting northward in time, it’s the threat of it mixing out that could hurt the much need surface Tds. However, the moisture concern is one thing that the GFS and WRF can agree on though. They both have a 55Td tongue advecting northward into western OK, by 0Z. I am afraid that 55Td just will not cut it though. This is something that I will be keeping and eye on starting 12Z Friday. Come on 60Td! Lol

Friday is just one of those days that I can sit, wait, and watch the LLJ and Td at least until 1-2pm. So I am not too uptight about it.

Mick
 
It's never too early to be pessimistic. As my friend Amos Magliocco once put it, "February is a harlot." Wise words indeed.

I was quite surprised to see such a strongly-worded Day 5 SWODY, considering it's February. One thing I've learned is anytime the phrase "100 kt mid-level jet" is used, it's usually a bad thing for chasers. I've wasted many hours of my life and dollars from my wallet chasing these rocket systems, and not once has it paid off. I'm inclined not to try anymore, lol.

Another thing I've learned is the day before often bears sweeter fruit than the advertised end-of-world event. Plus, anything on Friday would be in a better spot to chase. I refuse to go east of I-35 in February. There may be tornadoes out there to snag, but I'll let someone else grab em. I'm content to become a "bottom feeder" and wait for the easy, closer-to-home opportunities. If they come.
 
just took a quick glance at the 00z nam and i'm becoming more impressed by each run. mid to upper 50's td's with temps in the mid 60's with impressive yet manageable shear, by manageable i mean storms will not be moving at speeds that would've won them the pole at Daytona. i also really like the 1500-2000 j/kg of instability for this time of year.
 
just took a quick glance at the 00z nam and i'm becoming more impressed by each run. mid to upper 50's td's with temps in the mid 60's with impressive yet manageable shear, by manageable i mean storms will not be moving at speeds that would've won them the pole at Daytona. i also really like the 1500-2000 j/kg of instability for this time of year.

Yep, I'm getting a little more optimistic about Friday's potential across Western North Texas/Texas Panhandle. Again the NAM advects mid 50 dewpoints to the Kansas/Oklahoma border. Now it sugests a larger area of 1500 to nearly 2000 j/kg CAPE and a completely eroded cap along the dryline. Shear is more than adequate for supercells, and low level shear isn't bad at all. My fingers are crossed. This still looks marginal for surface based initiation, but chances seem to be increasing.
 
Ok, Friday setup is becoming more intesting in the way of storms. Storms that can get going on Friday will not be moving as fast as they will be on Saturday, and the fact that the storms will be more decrete on Friday evening. If models continue to indicate an eroded cape along the dryline, temps in the middle 70s in the afternoon, and mid 50 dewpoints, this shows all the signs of a classical early season severe weather event. Right now, dew points are already reaching the lower 60s along the coast and mid 50 in east-central Texas. I'm still going to stick with my gut feeling on this one and guess that the Northestern Texas and Oklahoma Panhandle, along with far Northwestern OK will the a good chase area on Friday evening. Living in the North Eastern Texas Panhandle, this setup is pointing right around my area.
 
The 1100 UTC SPC Day Three Outlook has 30% severe probabilities over northern TX, western and central OK and far southern KS. The hatched area goes from Abilene, TX to Pratt, KS north/south and from the far eastern TX Panhandle to just east of OKC from west/east. The discussion has some attention catching wording:
FORECAST SOUNDINGS ACROSS NW TX AND WRN OK LATE FRIDAY AFTERNOON
SHOW CLASSIC LOADED-GUN TYPE SOUNDINGS WITH 0-3 KM SRH INCREASING TO
ABOVE 500 M2/S2 DURING THE EVENING. THIS SUGGESTS SUPERCELLS WILL BE
CAPABLE OF PRODUCING TORNADOES. THIS COMBINED WITH 0-1 KM SHEAR
VALUES EXCEEDING 30 KT WILL MAKE STRONG TORNADOES A POSSIBILITY
FRIDAY EVENING...SHOULD STRONG CAPPING BE OVERCOME. IF MOISTURE RETURN ENDS UP BEING STRONGER THAN FORECAST...AN
UPGRADE MAY BECOME NECESSARY IN LATER OUTLOOKS.

Looks like Friday might beat Saturday to the first Moderate Risk issuance of the year.
I would chase this great looking setup except for two small problems:
1) I haven't gotten my equipment yet and am not prepared to chase
2) I have class on Friday:(

Otherwise, I would be packing my bags tonight and driving down there tomorrow.
My preliminary target if I were chasing this thing: Childress, Texas.
Oh, I wish this was April or May instead of February...aargh. Oh well, at least this bodes well for the spring.:D
 
I'm worried about moisture and the instability able to overcome the cap right now but there are many variables that are still not being resolved right now that I think could have a huge impact on Friday. With a cap this strong, I think a small subtle wave is going to have to be around to get storms going. My best wish is for a storm to develop about 4:00 on the dryline and then go do its thing (within reasonable distance from me of course :p). Basing this forecast off the 0z model runs, I interested at how they break out elevated precip in C. Oklahoma and I'm moderately concerned we're gonna lose all of our instability because of a grey kind of day. Once the main upper level support arrives, if we don't get a squall line right away we could get a broken line of supercells and that doesn't bode well for the areas that'll be hit overnight :( Either way, unless something changes I've been suckered into going out this early so hopefully someting happens before the sun sets :)
 
A nice set-up with some problems, like everyone else is saying. Looks to me like some broken stratus will probably be developing northward in the "warm sector" throughout the day with perhaps some light showers. I don't think initiation will occur on the dryline until strong mid-level cooling/uvvs associated with the incoming mid-level jet nose spread in and the dryline sharpens up... which looks to be right around sunset. This is a pity because I think the result will be several nasty supercells. Large hail looks like an obvious threat, but the tornado potential will depend on how quickly substantial MLCINH develops toward 06Z. I may be out there anyway, just in case initiation occurs earlier.
 
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A few observations:

1. I haven't seen this heavily worded a Day 3 in quite some time. There's enough verbage in here to make a chaser drool on his pillow. "Loaded Gun sounding", "Strong Tornadoes", "Very large hail", "Wind damage", "Bow echoes", and "Upgrade may be necessary in later outlooks". Pinch me I'm dreaming.

2. I've been pinched, and no dream. Helicity in this will make the storm and we really don't need a great deal of directional shear in this setup to get stuff going. Plenty of helicity and good shear will fuel this set up fine...*if* we can break the strong February cap.

3. SPC already has 30% hatched for a large part of Oklahoma, south central KS and north central Texas. Thus, their confidence seems quite high at this point on time.

I'm impressed again by the model consistency and moisture return to get this setup to materialize. As usual, being February, I have concerns about timing for one thing, for another, I havent seen a whole lot of Feb. setups that look this good actually *verify* but weather does not go by clocks and anything can happen.

I'd say this is one worth chasers getting out for.. might miss out on quite a season opener. :)
 
I inadvertently tagged the comments below into the weekend thread, which obviously should be here instead:

For 00Z Saturday:

ECMWF 00Z has 500 hPa feature near 4 Corners, dry line sharpening across P'handles - best instability CDS area, surface low N CO.

GFS 00Z - 500 hPa feature in AZ, dry line P'handles, CDS best instability region.

GFS 06Z - 500 hPa feature in 4 Corners region, similar surface instability as other models, surface low SE CO.

If I was out there, I'd probably head to CDS on Friday for a look around!

Overnight, instability increases over W/cent OK into cent KS - LLJ cranks up - nocturnal tornado probability seems quite high...models break out a fair amount of precip as dryline/cold front is swept eastwards as surface low deepens/lifts NE.
 
Some interesting developments since last night's models. When I viewed the 12z (21st) NAM this morning and saw the upper trough had speed up, I thought "it's just the NAM having some problems near the 60hr forecast timeframe". But the GFS has also speed up the upper trough just a little. This is significant, IMO. This will bring upper support to the Texas Panhandle/Western Oklahoma a couple hours sooner, increasing the chances for breaking the cap late Friday afternoon.

Others have mentioned that low clouds associated with rapid warm air advection will be a big obstacle. I see that being a problem further east in the warm sector away from the dryline. Without any upper clouds hindering solar insulation, mixing should be sufficient to erode a low cloud deck, especially near the dryline.

With each successive model run, it seems the chances for surface based convection initiating along the dryline continues to increase. I may be getting ahead of myself, but supercells, some tornadic, seem quite probable if the cap can break late Friday afternoon or early Friday evening. If dewpoints near 60 appeared likely I'd probably be too excited to work!
 
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