2009-05-12 FCST: KS,NE,MO,IA,IL

[Chris Allington]

Given the capping concerns with the Southern target. I'm starting to like the northern target more based on the 18z GFS (if it verifies). We will see if the trend continues on the 00z run.

It places low-mid 60 dewpoints along with low 80s temps in an area from SW Nebraska down to SW Kansas with some pretty good directional shear. Speed shear isn't terrible either, and looking at 850-500 mb crossover looks pretty decent. Theres a nice Theta-E tounge and CAPES in the 2000-2500 j/kg range.


EDIT: Took a glance at the 00z NAM & GFS. Both have a wider instability axis... however the GFS is still deeper with the surface low and quicker with moisture return as a result. I'll be watching this one tomorrow as I like the area in SW NE and NW KS. Say near the Imperial area if I were to pick now. It will be interesting to see how this evolves.

 

[Stan Rose]

Well, with a rare day off this marginal day is looking pretty good to me. Im eyeing NE CO/SW NE where the shear looks pretty good. Moisture isnt a given but it looks sufficient, and theres a real nice shortwave swinging in late afternoon. My main concern is the ghastly warm 700 temps to the SW. I'll make a go-no go call tomorrow night.

 

[Skip Talbot]

http://68.226.77.253/models/eta/central/CENTRAL_ETA212_ATMOS_LSI_48HR.gif

The WRF has been fairly consistent at showing an unbreachable cap. A cap index of 5 is going to take more than 50-55 degree dewpoints, a loosely defined dryline and a 40 knot jet to fire sustainable storms. This is when the cap is weakest too. It quickly strengthens after dark. I don't think the marginal conditions are adequate given the cap for this setup.

 

[Brendon Lindsey]

Well if i had to go solely off the 0z NAM I would head to Enid haha, I feel the cap is breakable, the 700 temps are just a little warmer then what I believe would be breakable. But , the GFS is a different story. I love the Skew T for Enid though, gotta take a look.

 

[Mark Farnik]

After looking at the 00Z run of the NAM, I'm thinking things could potentially get interesting in far northeast CO/southwest NE on Tuesday evening.

The NAM shows a nice bullseye of 2000 j/kg of CAPE, EHI values of 4.5 to 5, LI values of -5 and 0-3 km SRH of 300 m2/s2 right along the CO/NE border region at 00Z Wednesday. There is pretty nice directional shear, with southeasterly winds at 850 mb veering to due westerly at 500 mb. The speed shear isn't terribly impressive, but it's there.


The only thing that's concerning to me is that the T/Td spread will be reasonably large, with low to mid 80's surface temperatures and 55-60 degree dewpoints, LCL's are going to be on the higher side, so the tornadic potential is somewhat questionable at the moment, but definitely not outside the realm of possibility. However, if stronger moisture advection were to occur and we could realize 60-65 degree dewpoints in the target area, the tornadic potential would obviously be much higher.

Nothing about this setup stands out to me as overly impressive, but overall it looks more than adequate enough to support a few nice supercells with some potential for isolated tornadoes. And given that this is most likely the last chaseable setup in the Plains for a couple of weeks, it's only a 3 hour drive to the target area from Denver, and I'll be done with school, I'm planning on chasing it.

Based on the above parameters, my preliminary target is Holyoke, CO at 3 p.m. MST Tuesday.

 

[Brendon Lindsey]

12Z NAM Skew T

Well I have the understanding, that if a storm does manage to go up as far east as Enid, it would be the storm of the year basing it off this 12z run. If only the Cap was breakable *sigh* =/ I'm wish casting and wanted to show others this skew t. I suppose there would need to be more forcing also?

 

[Greg McLaughlin]

Tomorrow could be a waste of a good setup. Both the GFS and NAM are showing 700mb temps from near 13-16C across the area of interest tomorrow from southwest Kansas into northwest OK/Texas panhandle. It appears all of the ingredients will be in place, however I highly doubt a storm will be able to break through much less survive a cap as strong as the models are forecasting. It could be another waste of a day......*sigh*.

 

[Jeff Snyder]

Well I have the understanding, that if a storm does manage to go up as far east as Enid, it would be the storm of the year basing it off this 12z run. If only the Cap was breakable *sigh* =/ I'm wish casting and wanted to show others this skew t. I suppose there would need to be more forcing also?

In addition to a cap that looks like it will hold, I don't like that hodograph. We saw similar hodographs and thermo structures on March 26th (which had the Roll, OK, tornado, but little of anything else tornadic). The 0-3km vertical wind profile looks good, but there is almost ZERO shear above 3 km. Note that the hodograph essentially sits on itself from 3-7 km, which is indicative is essentially no shear in that part of the atmosphere. Yuck, no thanks! We also saw a similar hodo early last month, IIRC -- the low-level shear looks good, but shear above 3 km is pretty much non-existant. On both days that I'm thinking of, save for 15-20 minutes during the life of the supercell that produced the Roll tornado, we didn't see anything significant from any storm those times.

I'll be chasing, but I'm not too optimistic. With the look of the GFS and ECMWF forecasts of late, it appears very good for V2. What fantastic timing for Ma Nature to give us ridging in the west...

 

[Jared Farrer]

It looks better than it certainly was. NAM tends to underdo CAPE but it looks that the GFS is similar in the projected cape profile. CIN is awful and the NAM dosent want to break out precip at all! But if something were to get going, in the dodge city area, damn.

Looking at GFS forecast soundings for the DDC area CAP is huge but CAPE and winds are also big with more advecting in by 03z!
Could be an interesting day if things can pop and move through that area! Which I have seen happen, that area usually works some kind of magic and Ive seen similar setups that did go up big. That area could be monitored very closely via short fuse composites. I am not terribly convinced something wont fire further south and west and move into that area. Maybe get a thermal ridge setup like the other day.

The NAM forecast sounding for 12z already shows 1000 cape and cap for that area with advection occuring all day. I dont know about anybody else but that area looks decent to me.

 

[Mark Blue]

Since this system is close to home I am also watching this with some degree of excitement. The area I like is closer to the upper level support, which is a shortwave trough that will swing out into the central high plains late in the afternoon. An area of lee troughing will develop in this region which should provide some focused convergence at the surface. I am liking the SW NE to NE CO area, say in a box from Yuma to McCook to Imperial back to Holyoke. The cap has been well addressed in this thread so no need to beat a dead horse. If the dewpoints can get into the mid 50s, there may be a chance to break the cap, but it would seem that any storms that do go up will be high based. CAPE appears as though it will be near 2000 j/kg based on the data I've looked at, so if that can percolate under the cap in the afternoon temps forecasted to be in the mid 80s, maybe something will happen. I'll have my gear next to the front door in case I decide to pull the trigger in the morning. I can also put it away just as easily if I decide not to go!!

 

[Warren Faidley]

With such a large area of dryline possibilities, I would not be surprised to see at least one good storm somewhere along the line. One good thing about having VORTEX2 out, is that they will be gathering upper air data throughout the day and unless something has changed from the original VORTEX, this information will be shared with the SPC for outlooks and MD's.

W.

 

[Brian Stertz]

Looks like maybe some Caprock Magic is in order for the DL/WF intersection between Plainview and Childress TX...if the 00z NAM is to be trusted. Looks like LCL's get better by evening so whatever does fire should have an increasing trend on tornado potential as it moves off the Caprock. Like the looks of things tomorrow but too far for me to travel unfortunately. Best of luck to those heading off to be with the Vortex 2 masses.

 

[Bill Schintler]

Chase Target for Tuesday, May 12

Chase target:
Abernathy, TX (18 miles north of Lubbock)

Timing and storm mode:
Storms should fire by 6 PM CDT, with supercell storms likely. An isolated tornado or two is possible. Storms will evolve into a large complex by early evening.

Synopsis:
At the upper-levels, broad ridging was in place over the central CONUS with 12 hr 500mb height falls of -60m over the PAC NW. At the SFC, a convectively-reinforced cool air mass extended along and N of I-20 in TX. Area soundings (AMA, MAF, EPZ, and ABQ) all indicate extremely steep mid-level lapse rates along with warm (12-14C) at 700mb.

Discussion:
For the third straight day, strong capping will be the primary concern. Forecast soundings along the eastern TX panhandle into western KS indicate a strong inversion between 750 and 800mb, with 700mb temperatures of 13-16C noted in southwestern KS at the nose of a mid-level thermal ridge. Current reasoning is that sufficient heating should take place over portions of the central and southern TX panhandle to breach the cap; further N, where deep layer shear is more favorable, it now appears as through the convective temperature will be several degrees from attainable. Low clouds will continue to blanket much of the TX panhandle through 18Z, after which clearing will take place to the W of I27 from LBB to AMA. SFC temperatures should approach 95 to the S and W of a BPG to LBB line. Models (NAM, GFS, and UKMET) agree to initiate convection by 23Z. Strong instability should be in place, with MLCAPE’s increasing to 2000J/kg as steep mid-level lapse rates overspread LLVL dewpoints of 60-65F.

Models are in close agreement with timing and location of a compact shortwave, well S of the main jet, which will emerge from NM between 22Z and 00Z. As a result, deep-layer shear will increase to 45 kts by late afternoon. After 02Z, the SRLY LLJ will increase to 40-50 kts with storms increasing in coverage and intensity. LLVL directional shear and hodograph curvatures will increase after dark with SFC-3km SRH in excess of 500 m2/s2 FCST by 04Z.

- Bill

11:33 PM CDT, 05/11/09

Feel free to PM me for nowcasting

 

[Paul Austin]

Really liking the later NAM and GFS runs for srn TX panhandle and southward. Cap is looking breakable with a little help. 10 - 11 C much better than 15 C. Looks like there could be and OFB near the Red river by 0z from early day convection to focus development and impart a little enhanced helicity, and a slightly more robust dry line due to a weak impulse ejecting out of NM. Seeing at least hints of stronger h2 to h5 winds over or very near the southern TX panhandle as well. I'm certainly biased here, as I'm on a 2 wk chasecation with no flexibility of schedule. Remaining problems with this setup would include the aforementioned cap (yet not quite so nuclear further south), potential for cloud cover even west of the dryline, and modest but directionally nice shear. But hodos look excellent, soundings not as bad as earlier runs with essentially no cap by 0z in some areas, and 3km EHI values shoot through the roof in srn OK on the NAM run. Just like folks like to say about the weather, "If you don't like the current model run, just wait a few hours. It's sure to change." Of course that goes double in reverse for model runs you actually like, LOL.

Here are the 6z NAM and GFS soundings and hodographs for Benjamin, TX at 0z. Dewpoint depressions could be a problem in some areas, and the cap is very stout further north, but there are some things to be encouraged about in these plots. Hopefully, later runs and actually realization only improves, but that is still to be seen.



For the southern target, I could see a cluster of perhaps elevated cells initiating near Lubbock around 22z, moving generally east-northeast-ward toward Childress, and becoming more surface-based and discreet as they approach an area of lower LCL's, higher cihn, and better helicity. So I think our initial target will be somewhere near Childress, TX with adjustments throughout the day. Good luck to all who brave the V2 and chasecastion hordes. Lots of SDS going around. Be safe! Hope to meet some of you out there face-to-face.

Paul

 

[Warren Faidley]

Target for today: Lubbock to Childress, Texas. Pretty simple forecast today, considering cap, DL and best shear. Road network/terrain will also be considered as target(s) are defined.

Good luck to all. Reserve your roadside parking early...

W.