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

[scott r currens]

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

That is an awsome quote! It is even better knowing that Amos is planning on chasing Saturday. I guess he has money in hand.

 

[Justin Bailey]

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.

 

[Jim Bishop]

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.

 

[BrandonWhittington]

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.

 

[Mark Farnik]

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.

 

[Chris C Sanner]

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 ). 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

 

[afischer]

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.

 

[Jeff Miller]

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.

 

[Paul Knightley]

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.

 

[Jim Bishop]

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!

 

[afischer]

I like Jim's assessment. I think getting the uvvs and mid-level cooling to arrive on time (i.e., before sundown) is important, cuz I'm afraid some weak capping will hang on which will be tough to break until the upper help sharpens the dryline up.

Another thing I've noticed in GFS and NAM soundings 03-06z, in addition to the beautiful sr hodographs that develop with the nocturnally enhanced LLJ, is the very impressive instability that develops in association with the steepening lapse rates aloft. LIs pushing toward -7 and a solid area of 1500 j/kg MLCAPE sure isn't too shabby for a late February evening.

 

[Gabe Garfield]

As far as chasers are concerned, I believe Friday will be the main event. As Jim already mentioned, the timing of the main wave is a bit faster than previously progged. Though this will have little impact on what happens (i.e., tornadoes), it will have a large impact on where it happens. With the faster timing of the system, forcing for convection will occur sooner and wind fields will increase sooner which will increase the potential for daylight tornadoes in the Sooner state.

A few thoughts about this potential event:
First, I think the timing of the wave is particularly good, according to the latest model runs. Most significant tornado outbreaks occur when increasing flow (at all levels) is coincident with peak heating/thunderstorm initiation. This will likely be the case Friday as mid and upper level flow increases dramatically during the afternoon and evening hours.

Also, the 12Z NAM shows a narrow instability axis in place by 00z Sat (6 p.m. Fri). The maximum in CAPE is progged to be in NW OK (~1500 j/kg). On the other hand, the NAM forecasts the greatest low-level shear (0-1 km) south of I-40. Thus, the best juxtaposition of favorable parameters appears to be close to I-40. This far out, it's pointless to banter about model output on such a small scale, but it is interesting to discuss possible scenarios (based upon experience and climatology).

I think the most likely scenario (see 3/27/04) is that several storms will form along the dryline (all potentially tornadic), but the greatest threat of tornadoes will exist on the northern end of the line. Temperatures will be slightly lesser in NW OK, but this could be beneficial in lowering the LCL heights. Otherwise, the environment should be relatively homogeneous down the dryline.

Furthermore, tornado outbreaks in Oklahoma during the month of February are not unprecedented. On February 17, 1961, 9 significant tornadoes (8 F3 s, 1 F2) impacted C/E Oklahoma including a large tornado in Oklahoma County. See the following 500 mb plot: http://bangladeshtornadoes.org/UScases/021761/02186100zh5.gif

Finally, CAPE is forecast to increase through the overnight hours as the 500 mb low approaches and cools temperatures aloft. Friday night could be very long for Oklahoma forecasters.

Gabe

 

[afischer]

First, I think the timing of the wave is particularly good, according to the latest model runs. Most significant tornado outbreaks occur when increasing flow (at all levels) is coincident with peak heating/thunderstorm initiation. This will likely be the case Friday as mid and upper level flow increases dramatically during the afternoon and evening hours.

I guess that I'd argue the timing of the wave is really not that good if we're looking for daylight tornadoes. The sun sets around 615-620pm in the general target area. If the sun set more like at 8 or 9, then I'd consider the timing to be ideal.

FWIW, the NAM hasn't even a whif of convective precip by 00Z... though the BMJ scheme is just starting to "activate" on the northern portion of the dryline at 00Z, over SW KS. (http://www.wxcaster.com/CONUS_ETA_700_GPHTMPRH_60HR.gif) Based on what's been discussed previously (initially weak dryline convergence), I'd say this looks fairly realistic. But, like everyone else, I'm hoping things initiate earlier rather than later.

 

[Jim Bishop]

FWIW, the NAM hasn't even a whif of convective precip by 00Z...

The NAM (though before the recent modifications) also did not show convective precip along the dryline over Western Oklahoma for the May 29, 2004 outbreak on the 00Z May 29 run. It did, however, show the CIN erode by 00z. The point here is even though the NAM fails to develop convection, it suggests CIN will be eroded, which would imply convection given all the other conditions. If it showed a cap still in place at 00z, I'd be very concerned about initiaion. But, obviously if it did fire convective precip it would add more confidence to actual initiation!

 

[afischer]

The NAM (though before the recent modifications) also did not show convective precip along the dryline over Western Oklahoma for the May 29, 2004 outbreak on the 00Z May 29 run. It did, however, show the CIN erode by 00z. The point here is even though the NAM fails to develop convection, it suggests CIN will be eroded, which would imply convection given all the other conditions. If it showed a cap still in place at 00z, I'd be very concerned about initiaion. But, obviously if it did fire convective precip it would add more confidence to actual initiation!

This is a good point; one certainly shouldn't take convective precip as gospel. I think there's many differences between Friday's setup and 5/29/04, though... the primary one being that 5/29/04 had strong moisture convergence along the entire length of the dryline. In contrast, mesoscale (as well as synoptic scale) focus looks pretty sad for Friday until around 00Z, which was my reason in supporting the NAM convective precip prog that I described. If the cap breaks anyway at 4pm, I'll be jumping up and down along with the rest of you.