4/21/04 FCST: OK/northeast TX/western AR

Kevin Scharfenberg

The front that is stalling south of OKC late Tuesday evening should be quasistationary, or slowly lift north Wednesday as a low pressure deepens in southwest Oklahoma or northwest Texas.

Low 60s dewpoints should pool along this boundary, with CAPEs approaching 2000 J/kg. Surface winds should be nicely backed near the remnant boundary, and due to isallobaric forcing as the low pressure develops to the west. That should yield shear profiles that are similar or slightly better than seen on Tuesday. Looks like another supercell day with potential for a few weak/brief tornadoes. Given what happened in IL/IN Tuesday, setups like this cannot be ignored!

Initial target: Shawnee, OK.

Discuss here...
SE Oklahoma

Probability of Severe Thunderstorms is 62%
So with that 62% it corresponds with my charts on.........

Severe Thunderstorm Risk.

Type of Event.

Thunderstorm probability is 80%.
no Thunderstorms expected
Slight Chance
Run For the Hills

Forecast Discussion.

Dewpoints in the mid 60's and temperatures in the lower 70's make for an unstable atmosphere today. CAPE values are at 2000, so expect very explosive developments with this dryline passing. 850MB Low Level Jet showing 30-35knots, enough to support long lived supercells. 500MB winds at 35 knots so damaging straight line winds are possible. Helicity at 150, so weak Tornadoes Are expected in the F0-F1 range, and a Tornado Watch has been issued by WIRT.Hail values at 325, so Severe Hail is a threat.

Severe Risk: High

Main Concerns: Moderate Damaging Winds, Large Hail, and Isolated Tornadoes


So with said my Target is Western Central Arkansas, Right ON the Oklahoma Border.

Kevin Martin
21 April

I like what I see on the 00z eta and what is more important, is that the 00z gfs is almost identical. The sfc dp's look to be in the 60-65 range and temps 70-75. There looks to be a nice neg. tilted shortwave on the 700mb map making for some steep lapse rates I suspect. Add to that the 500mb vortmax to the west, a lifting warm front and projected helicity values of 400 to 500 in far SE OK and we may have a nice day. Don't know how accurate those helicity figures are, does anyone see a problem with those or a reason why they would be inflated?

Only problem is we will be chasing thru the jungle.
I am really liking my hometown today of Velma to start with. With the Max tornado and overall storm potential just to my east (right now) I am liking V-A right now. But I'll probably settle with Ratliff so I have highways going each direction. I'm liking today though, hopefully I see my 3rd 'nader of the year.
Wow... check out that RUC! 2000-2500 CAPE and >300-550 m2/s2 0-3km helicity south of I-40 and east of I-35 by late afternoon. Yowsa!

Now, I'd start saying something about the risk of violent tornadoes, but the mid-level flow weakness may preclude that. RUC has 500mb winds ~35kt... meager. However, this also means that we'll likely have quite slow storm motions (I thought the 0z ETA how like 25kts storm motion). . I'm stuck in an exam until 4:45pm, so I'll have to head out after that. Between today and tomorrow, we could end up with quite the two-day tornado event...
After looking some more I might try the apparent triple point setting up. In that case, Lindsay or Elmore City looks good as I want to be a bit south and east of it (plus the highways going out are a good sign). My target will change 10 times today though. So we'll soon see.
I like the ARD to OUN area for initiation, perhaps under the clear area south of the cirrus shield. Would be nice to see that thing burn off from south to north so you could follow the tongue of higher dewpoints closer to I-40 and move into those easterly surface winds. With your 850 winds already backed you could use the extra turning at the surface to increase your SRH. The 0-1km shear along the river doesn't look too impressive right now unless 850 veers some as the jet picks up. I like those east winds and you've got plenty of juice up there--ARD is already 70/66.

Dryline is punching hard from west Texas with very dry air behind it and stout westerlies. No question this is going to pop some storms. Looping the current dewpoint contours from CAPS you can see the bulge over the river which should push west and place the ADM to OUN area just north of that feature, further enhancing convergence and backing the surface flow a little more. I would maintain a position 25 miles north-northeast of this feature and shadow it across. Ardmore is a good start or maybe Paul's Valley.

I expect supercells but will have to see a more robust low level jet before thinking about storng tornadoes. If you can get some better low level shear, small spinups seem more likely. Once the jet kicks in, however, the show will be on.
The 18Z eta forecast suggests some nice backing surface winds @OUN though velocities aren't that impressive. Judging from forecast CIN, there's no garuntee for discrete storms.
Ok, I'm definately going for Lindsay, OK as I have routes in every direction out of there. Also real flat out there. I hope to see some of you guys out and about. Happy Hunting!
After morning analysis (I feel silly calling it that), I'm still not settled on A target town, more of a target zone. It's obvious just east of 35 is the place to be, but exactly where? RUC seems to favor Ardmore with its precip map and UVVs, but I'm thinking I want to be a bit further north and a bit east, to take advantage of the better backed winds closer to the boundary. Jo likes Shawnee (Kevin S' target), I'm leaning more towards the Ada area. Ada has an insane road network that allows quick escape in about 6-7 directions, so that is a solid choice in my mind. However, there are four of us today and we still have half the brain to discuss with.

I'm a little confused on exactly how the front/boundary in central/eastern OK is supposed to behave....stalled for a while, slow migration south then a northward retreat, or a slow northward retreat from its current position. RUC seems to break out initiation points in different areas, which to me is indicative of a gradula northward movement from its current position (without any subtle southward sag between now and then).

Best thing about this situation, a backyard event (to begin with anyway), so we should be able to sit here and monitor conditions well into the day. I was very confident yesterday about our tornado chances, and I'm as confident today. I don't care about the strong tornado potential, only the torndo potential in general. I believe the stage is set for a nice round of tornadic love, greater than what happened in NE portions of OK yesterday. With SRMs that are cooperative, and a slow moving boundary, I see no reason not to expect a few cyclic tornadic cells. Might not be a tornado armageddon, but I don't think a few 3-4-5 tornado storms are out of the question.

Might post again later if we make any significant observations/adjustments. Good luck to everyone out there, bring your chain-saws, and be safe 8)

SPC's 1630Z is very aggressive, indicating the chance of a significant severe weather event. It's obvious that cloud cover is substancially less than models indicated in prior runs. I have a strange feeling that, if (a) the cloud shield can burn off rapidly in the next 2-3 hours and (B) upper air obs show stronger winds at h5 than currently forecast, SPC will go High Risk with the 2000Z. I'm certainly not trying to sound the alarm, but the parameters speak for themselves.....the potential is there for a major event, given a few subtle changes.
Since i have a drive from se ks, i am gonna go to henryetta ok and decide where to go from there. It is a 3+ hour drive and things should be getting ready to initiate by that time. I will probably stop by a library and check out obs and new spc and go from there. Good luck everyone.
I am getting off work now and heading towards west Oklahoma from amarillo. Will get wx updates once i get to elk city.
Norman Will Get Hit

Norman is going to get hit today!!!!!

Warm front has stalled on I-40, the models are underestimating the CAPE which will most likely reach 3000 J/kg today in Central Oklahoma!

Norman and Moore are in line for any tornadic supercell that goes up.

I was just informed OUN and FWD are doing special 18Z soundings for updated wind fields and determination of CAP strength.
As much as I hate to admit it, I agree with Simon's reasoning...central Oklahoma could get tagged today. Reminds me a lot of May 8th last year. Of course, there are different atmospheric parameters, but the threat is increasing as the day progesses and the SPC is moving the risk further into central Oklahoma. The Norman dome has a good chance of breaking today, and I'll be in an Atms. Dynamics exam! LOL.

Ok, so after going over the most recent RUC data, Jason and I will be heading toward Pauls Valley here in just a sec to set up shop there. We will wait there for initiation and then decide which way we want to go. Hopefully, stuff should go up around 3pm to the west of there. Pauls Valley has several good ways out of town so we should not have any problems getting out of there. Everything is lookin good!
Re: Norman Will Get Hit

Originally posted by Simon Brewer
Norman is going to get hit today!!!!!

Warm front has stalled on I-40, the models are underestimating the CAPE which will most likely reach 3000 J/kg today in Central Oklahoma!

Norman and Moore are in line for any tornadic supercell that goes up.


Try not to sound so excited....a bunch of us live here/there
I think this is turning into a very dangerous sitution. Latest RUC run keeps east-southeast or at least southeast winds east of I35 by 0z. Because of this, the RUC is showing helicity >400-500 (!!) by late afternoon east of I-35. This is nicely juxtaposed with CAPEs in the upper 2000 range (2000-3000 depending upon location), which leads to an incredibly favorable instability-shear profile. Deep-layer shear off the 12z ETA run shows 0-6k deep-layer shear ~50-55kts over southern 1/2 of OK this pm too.

Picking a target location is proving to be very difficult! I am inclined to go for any sups that may ride along the warm front / OFB near I40, but the best shear per latest RUC remains south of I40 and east of I35. So, depending upon what happens from 3-4:45p, I will likely aim just south and east of here (Norman). Good luck to all! Let's hope these beasts stay out of populater areas!
Personally, I'm not too high on the setup today. I don't think the shear supports significant tornadic activity in Oklahoma, and think that anything substantial (i.e., stronger, more long-lived tornadoes...not brief spinups) that may occur will hold off until the low-level jet kicks into gear around sunset, east of I-35 and along/south of the windshift. The prospect of that may be enough to make me head out, but based on the RUC, the 18Z OUN sounding, and current profiler obs I'm not really excited about the setup and expect most, if not all, of the tornadic activity to be sporadic and weak in nature. At least I live right here, so if something starts to happen it's easy to hop into my car and roll out. Of course, one always has to be careful when using model progs, so I'll be keeping a close eye on the situation as it develops this afternoon. If nothing else, it appears we should have some good supercells today.