5/10/10 FCST: TX / OK / KS / CO/ MO

[Bill Schintler]

Chase Target for Monday, May 10

Chase target:
Enid, OK

Timing and storm mode:
Supercell storms should develop along a dryline after 4 PM CDT. All modes of severe weather are likely, including tornadoes. Storm motion will be at least 30 mph towards the northeast during initiation, and increasing to 50 mph or more by early evening.

Discussion:
A transition to an increasingly amplified jet stream will take place over the next 72 hours as a series of disturbances embedded within this flow eject from the trough base into the Plains. On Monday, a lead 100kt H5 streak will overspread the panhandles and then OK. At 00Z, a 100m H5 12hr height drop was centered over SRN CA. Looking ahead, another potent shortwave will pivot through the trough Wednesday, with the system transitioning from neutral to negatively tilted. At the SFC, low-pressure over WCNTRL KS will track slowly towards the east Monday. A synoptic WF will extend ESE of this feature. One or more mesoscale outflow boundaries will likely exist S of the main WF because of the departing MCS. Timing and location of this convection is key to the degree of AMS recovery in the target area, especially towards the N in KS. A DL will mix rapidly EWD and sharpen during the afternoon, reaching I-35 in NCNTRL OK shortly after 00Z.

Moisture return is a concern, with H85 dewpoints AOA 16C currently confined to SRN TX, however strong NWD moisture transport will take place between 06 and 12Z as the LLJ increases to 60 kts. OUN and FWD soundings both indicate increasing moisture in the H8-H9 layer. The 00Z NAM has initialized well to SFC and H85 moisture in this area. Elevated convection will increase overnight over much of OK at the nose of the strengthening LLJ. This precipitation will lift NE of the area during the morning; however, with SC lingering into early afternoon. Low cloudiness should erode from W to E by 21Z, allowing for moderate to strong insolation. Upstream 00Z soundings (AMA, EPZ, ABQ, and TUS) all indicate nearly dry-adiabatic mid-level. lapse rates. Differential advection of this EML with moisture from the S will result in strong instability with MLCAPE’s increasing to 2000J/kg along a narrow axis immediately E of the DL.

Once storms initiate, this instability coupled with impressive shear parameters and low cloud base heights will be supportive of a full spectrum of severe WX, including supercells and tornadoes. SFC-H7 shear vectors in excess of 50 kts, nearly perpendicular to the DL, will promote a discrete storm mode. LCL levels AOB are also indicated E of the DL. Extremely rapid storm motion is expected, with storm speeds increasing to more then 50 Kts as the ULVL streak approaches.

- Bill

9:30 PM CDT, 05/09/10

 

[Matthew Crowther]

00Z NAM has some bad signs- 500MB vort max is more compact with PVA confined to KS. At the same time, it has very little CAPE in KS, and the forecast soundings in OK have the infamous CAPE robber showing up. Will this end up being at least somewhat of a disappointment? I always get nervous at this point in a highly anticipated scenario, do not like to see last minute less hopeful signs. One good thing, perhaps this will prevent SPC from going high risk, which would probably put the final nail in the coffin...

 

[Joe Acord]

Here is the quick and nasty from me.

We are heading out around noon to the airport south of Medford, OK. Right now it looks like the left over boundaries are going to be hovering in the N-rn part of the OK. Initiation should begin around the 21-22z time frame and we are going chasing for some naders...

All the models, and that includes the GFS, show a very dynamic weather set-up so it would be silly to grab the golf clubs and hit the course instead of chasing tomorrow.

I personally like the shear levels north of I40 and hope that if we can get something discrete to fire up to our SW, we are going to be sitting in a golden position.

Everyone be safe, don't act like idiots, and good luck. Also, let's all pray, in whatever way you do, that no one dies tomorrow. Last thing anyone needs is a town getting wiped away as we enjoy our hobby. Stop and Assist in any way you can.

Side note: I told people I know this could be the Super Bowl of storm season, so as the cliche states "Get your game faces on, strap it up, and let's get out there"

Joe Acord

 

[cdcollura]

Good day all,

Monday, May 10 appears to be one of the most dynamic setups this year, so I won't repeat all the great replies and everyone's word on this thread. The biggest issue I see (besides crowds) is the storm motion.

This is a setup where getting on it early is the key. It's not that the storms will first be supercellular then go linear, but become more numerous and with an increase in speed with the attendant speed maximas aloft.

I am currently spending the night in a quiet little motel in Medicine Lodge, Kansas with a full of furniture and cozy room and great wi-fi ... I am so suprised I am the ONLY chaser here. I like the target area as I probably will not have to adjust it in the morning. Enid, OK is also a good starting point for some of you folks as well.

I saw someone's post earlier on the "stop and assist" subject. This is NOT something we want to do, but may HAVE TO if the un-thinkable happens tomorrow (aka, town gets hit). I dealt with that a couple of weeks ago in Yazoo City (Mississippi) and going home choked up is sad. Be safe everyone!

 

[Chris Hayes]

Looking at the position of the convection in KS and OK I personally dont think it will be hard to get sufficient clearing in the risk area for tomorrow. The storms are expanding in aerial coverage, BUT they are not backbuilding to the west any, and appear to be moving at a fairly decent clip. They're already in eastern OK and KS so it shouldnt be too hard for them to pull out of the area and their cirrus fields to burn off in the morning/early afternoon. If anything these might help the situation a bit by throwing around some boundaries for storms to play with. Time will tell.

 

[Chris Sokol]

An observation from watching the radar tonight; The precip forecast for overnight in Oklahoma seems to be developing further East of the I-35 cooridor than expected. If this trend continues through the night, it would lessen the probability of a debris shield sitting across Oklahoma through the morning/noon period tomorrow.

 

[E Hale]

Also, Dew points are already higher in C. OK than expected. Current is 52 in Norman.

 

[Adam Adkins]

The one thing that is concerning me about tomorrow is a lack of moisture. Neither the 00z GFS or NAM show any measurable QPF in OK. However it looks like moisture improves after 00z but that may delay the outbreak a bit - I seriously doubt these fast-moving supercells are very safe after dark.

 

[Jeff Snyder]

I'm not convinced about tomorrow's tornadic supercell coverage tomorrow. The following is based primarily on the 00z NAM... The mid-level cold pool (i.e. 500 mb temps) glances northern Oklahoma during the afternoon, with the bulk of the cooling aloft in N of the OK/KS border. Though the NAM has the dryline W of I35 at 0z, it has the cold front rapidly overtaking the dryline and brings the cold front all the way to the KS/MO by 6z. We should have some light until 2 UTC, but I don't know what the surface boundary pattern will look like at that time.

I'm extremely nervous about the incredible rapid destabilization that will need to occur tomorrow if the 00z NAM is anywhere close to correct on the surface thermodynamic characteristics tomorrow morning through mid-day. Heck, at 18z (that's 1 pm CDT!), the NAM has almost no SBCAPE in Oklahoma or Kansas, with temps in most of Kansas only in the low 50s. By 00z, temps in KS are still only maxing out in the low-mid 60s, and the 65 F isodrosotherm is apparently going to make it all the way to the OK/KS border. If temps actually do verify according to the NAM forecast in the warm sector in Kansas, I'll be very worried about initiation and/or storms sustaining themselves in the face of extreme shear. How wide will the destabilized warm sector be tomorrow? If we only see a narrow warm sector, will the storms reside in the favorable thermodynamic zone long enough to mature and produce significant tornadoes, or will they move quickly out of area of appreciable CAPE? Note that the 00z GFS is considerably more bullish in developing a potentially-unstable warm sector as a result warm sfc temps forecast across most of the target area. The 21z SREF guidance also supports the GFS solution much more than the 0z NAM solution, with the ensemble mean 2m Td and CAPE fields similar to the GFS. The same 21z SREF data also are more bullish with precip down to I40 during the late afternoon and early evening. As such, perhaps the 00z NAM is just going to be a terribly bad forecast... Right now, the 6hr forecast (valid at 6z, or in 1 hr from the time of this post) from the GFS is more bullish with Tds in the TX panhandle compared to the NAM; current obs suggest that the surface dewpoint verification likely will be between the NAM and GFS forecast.

There are almost always some "cons" and sources of concern for a setup, and I'm not sure I've seen a "perfect" setup. However, I have some pretty great concerns for tomorrow and am far from convinced this is a slam dunk violent tornado outbreak. That is NOT to say I don't think the result could be so dramatic -- you just can't ignore >65 F Tds beneath such extremely strong flow. However, if I awake to see widespread stratus and some showers in Oklahoma, and if it looks like the NAM 2m forecast is verifying better than that from the GFS, I'll be concerned about the necessity of rapid destabilization. Fortunately, this is only possible as a result of the very strong ageostrophic flow and low-level response associated with the approaching short-wave trough. Again, the 00z GFS is much, much better in terms of destabilizing the warm sector through the day (the CAPE fields at 18z from the 00z NAM and 00z GFS are incredibly different). Interestingly, the 850 mb RH forecast from the GFS hint at more widespread low cloud-cover compared to the NAM (which indicates some clearing S of I40 ahead of the dryline before 18z).

It could be an epic day in terms of strong/violent tornadoes, and the fast storm motions greatly increase the prob of having long-track tornadoes. This is not to say, however, that it's a great forecast from a CHASING standpoint. Certainly, nothing like 5/12/04 (Attica), 6/17/09 (Aurora), and the myriad of other incredible chase days that featured cyclic tornadic supercells that moved relatively slowly through areas with good road networks.

Target: Doesn't really matter, since I'm with V2. However, I like the area along the OK/KS border E of I35. It'll be important to target the area well downstream (50+ miles) of forecast initiation as a result of the fast storm motions. I'm concerned about the lack of initiation on some of the high-res models in Oklahoma, and, with the best mid-level cooling to the N, I guess I'm inclined to be as far north as I can while still in >64-65F Tds. If destabilization can occur more in line with the GFS than the NAM forecast, I'd probably go for a HIGH risk as a result of the potential for long-track violent tornadoes.

EDIT: Sorry for the book-length post here... I am becoming a bit more optimistic with time as I further interrogate the GFS and SREF output (in other words, as I spent more time with solutions other than that from the 00z NAM). I'm curious to see the 4 km NSSL WRF come in, and it's Td and MUCAPE forecast is more in line with the GFS than the NAM at this point (at least through 17z tomorrow).

 

[CZandbergen]

Very difficult forecast for tomorrow from where I am sitting. The dry line is going to be further east than most of us would have anticipated and there is still a fairly large divergence between the NAM and the GFS on the 0Z run.

If the models are to be believed we will have a fairly stout CAP which will quickly erode after 21Z. The real question then becomes where initiation will occur. My feeling is the best bet is around a PNC to Chandler line. Anything further west than that and there is no way you will ever keep up with the storm motion. I am seeing ~35+ ENE motions as a best case and probably more than that. Assume we get a right mover and we can hope for 35kts. One thing I am sure of is I want to be down stream of the storm as with the predicted motion I will need about an hour to make sure I am in the right place due to the difficulty in pin pointing initiation.

What I think the models are missing are the OFBs associated with the ongoing convection that is quickly shifting east tonight. My plan is to look for the dominate OFB intersection with the dry line and position myself about 60 miles downstream around 21Z. That is my thinking as of now. A close look at the 12Z run and surface conditions will help me make the call in the AM. There is not enough data to do that as of now and I think everyone should be thinking more east than they are as of now.

I will be leaving Tulsa solo around 18Z with the intention of cheating it NW probably on 412. If anyone wants to tag along PM me. I could also use some nowcasting help. PM for my cell.

Best of luck and stay safe!

Casey

 

[Eric Bucsela]

These cases where the moist/warm advection has to happen fast make me nervous too. I'm just thinking May 6 of this year, when the dewpoints in N KS did recover, but not as quickly as the models - even 12 hrs in advance - had predicted. Of course, Attica KS 5/12/04 had the 60+F dews already in place at least a full day before, from TX to the Dakotas.

And as Matt Crowther just pointed out, the 00Z NAM now keeps the good instability in OK, separate from the good dynamics in KS. FWIW, GFS has stuck to its guns the past few runs and still progs decent moisture in KS, per tonite's 00Z run. (BTW, it is cold and drizzly here at ICT!)

 

[Chris C Sanner]

Excellent post Jeff, definitely very close to what I'm thinking. This whole thing seems completely out of sync, and contrary to what many may think, Tornado outbreaks don't just happen. There have to be a variety of components come together and just the right time and right now I'm seeing models throwing out solutions which are all over the place.

The NAM's solution is pretty bad for the tornado outbreak thesis because of the reasons Jeff mentioned earlier along with the shortwave's timing being a bit too fast. SFC winds along the dryline are west of due south across the warm sector by 0z, that's just not going to be good for anything if that verifies, regardless of the rest of the setup. The GFS's solution isn't bad, except it too veers sfc winds ahead of the dryline by 0z except in Kansas, but even then profiles don't scream strong/violent tornado potential.

When you add in the fast storm motions (I'd call them extremely fast) and the quite unfavorable terrain/road networks across all but a small sliver of SE Kansas with the likelihood of extreme chaser convergence making it impossible to keep up with those storms on top of all of that and you get a rather bleak picture for tomorrow chasing wise.

I'm not ruling out a tornado outbreak, but I think it's very premature to be expecting such a solution given some major problems with tonights model runs. And even if the outbreak scenario unfolds over the current projected terrain, the chasing won't be very good due to storm motions and poor road networks. It's really a hard luck case right now. My excitement would be far greater if the dryline were setting up about 40 - 60 miles further west, but I see nothing but frustration coming for chasers one way or another tomorrow.

 

[Brandon Sullivan]

From My Blog

Upper level divergence associated with the left exit region of mid level jet, aided by impressive forcing and diurnal heating and instability should spark a few isolated supercells on the northern edge of the dryline, immediately east of the surface low, across southern and central Kansas. Here, low and mid level wind profiles favor strong tornadic supercell potential, in a region characterized steep lapse rates, and 50kts 0-6 KM Deep layer shear below impressive H5 jet streak and ~90kt H25 flow.

Further south along the dryline into central Oklahoma, development will be more contingent upon the shortwave progged to cross the region in the late afternoon hours. In this region, impressive shear values and incredibly steep lapse rates will favor supercells with extremely large hail, and the potential for strong tornadoes. LCL levels of >700m will be found across the dryline. In addition, storm motions of 45-55 MPH will lead to the potential for long track tornadoes as well.

At this time my preliminary target area would be very near Wichita, KS..

 

[Jason Bolt]

Well SPC just went high risk w/ the day 1 over a small area in NE OK/ SE KS. I'm sitting right in the middle of it and we've gotten off and on rain for about 3 hours. Not sure how that will play in tomorrow but tonight's cells will lay down some decent boundaries for tomorrow.

On an unrelated note, lightning just hit the water tower in Columbus, KS and apparently the tower split open and is flooding the town!

 

[Chuck Robertson]

Okay, here we go! SPC just pulled the trigger and went High Risk for Monday. Interestingly, its centroid is shifted it a little further south than the centroid of the earlier Moderate Risk area.

Violent tornado outbreak or not, for all us weather freaks, Monday will be one very interesting day!

Edit: Well Jason, you beat me to the punch by 2 minutes!!!!