4/20/04: FCST: Central/Southern Plains

[Jeff Snyder]

As perhaps best said in the am AFD from OUN:
"IF WE COULD GET SOME DECENT SUBTROPICAL MOISTURE IN HERE IN THE FORM
OF 70-ISH SFC DEWPOINTS INSTEAD OF A BUNCH OF CIRRUS FROM THE
PACIFIC...THIS MIGHT BE A WEEK TO REMEMBER AROUND HERE. IT STILL
MIGHT...BUT AS IT IS WE ARE MORE LIKELY TO CONTEND WITH DEWPOINTS IN
THE LOW 60S AT BEST ALONG WITH A LOT OF HIGH CLOUDS FOR MUCH OF THE
NEXT 4-5 DAYS. BOTH WILL LIMIT INSTABILITY WITH MAXIMUM SFC-BASED
CAPES ON THE ORDER OF 2000-2500 J/KG EACH AFTERNOON...PLENTY ENOUGH
FOR SEVERE POTENTIAL EACH DAY BUT NOT THE GODZILLA-LEVEL INSTABILITY
NEEDED FOR WIDESPREAD AND/OR SIGNIFICANT OUTBREAKS"

Got that out of the way... Tomorrow does appear like it could be another severe day across portions of eastern OK and KS, and western MO later. CAPEs should be able to climb >2000 j/kg, as a negatively-tilted trough approaches from the west. My only tornado-related concern regards low-level shear. The 850mb low is progged by the ETA to be up into eastern NE by 0z tomorrow, with the best 850mb winds east of the instability axis. This shifts the area of best helicity eastward in western MO/AR and points east from there. In addition, the front/dryline is progged to be oriented northeast-southwest, with significantly veered winds ahead of it (sW surface winds indicated by the ETA). I'm hoping that overnight convection can give us a boundary to work off of and back the surface winds a little... Right now, however, I'm thinking the ne OK and se KS corners are looking pretty good, with a slight favor towards ne OK because of the better 850 winds.

 

[Michael Shively]

From my perspective....At least at this point i think all the "good" action will be in southern KS and Northern OK and PROBABLY develop into a squall line and head east from there....I think MO will pretty much will be a non-issue as far as tornadoes go....but i guess we will see...and i hope i am wrong.

 

[Jeff Snyder]

Well heck, Mike Morgan has outlined mainly points east of I-35 and north of I-40 in a moderate risk tomorrow... But hey, Mike said it would be like that....

Not much change with the latest 18z ETA... Instability still progged to be decent, with 2000-2500 CAPE through much of the eastern 1/3 of OK by afternoon and climbing to near 3000 in southeastern KS. The cap shouldn't be any problem tomorrow, as heating decreases CINH to very breakable levels by afternoon too.

My main concern continues to be weak low-level shear. The ETA has been forecasting only minimal 0-3k and 0-1k helicity over eastern OK and KS tomorrow, with 'values' only near 100-200 m2/s2. This can be attributed to two things: the 850mb jet axis shifts eastward in western AR and MO by afternoon and evening, and surface winds are progged to veer to the southwest. If this does happen, it'll likely pretty much eliminate much risk of tornadoes.

That being said, I am banking on an organized complex developing tonight over the OK and southern KS. I'm really hoping this can lay down a nice outflow boundary to provide a shear axis to enhance tornadogenesis... Guess we won't really know that until tomorrow morning...

EDIT: Shane brings up a critical point in the next post (I didn't want to make a new reply just for this). The models (specifically the ETA) haven't been doing very well with the smaller details in the past week, and not just in regards to low-level moisture in the Gulf... Even the 12Z ETA yesterday (Sunday) didn't initiate convection over eastern NE in the afternoon. I'm chompin' at the bit to start talking about the signficant system progged to come through Thurs/Fri, but I was reminded last week of how not perfect (to say it lightly) the ETA and GFS, especially past 36 hours. Just keep that in mind...

 

[Shane Adams]

The ETA doesn't really worry me lately, because it's blown a lot of days in the past few weeks. I'm more apt to wait on the RUC (again) in the morning and compare the two. This year, I've simply found the RUC to be more reliable; it nailed the western OK rain yesterday morning, the latst in a string of recent triumphs.

But while we're playing here, my initial target is Emporia, KS. This will no doubt change, hopefully shifting a bit west instea of east. But either way, I've taken tomorrow off and we have a brand new motor in the weather wagon, so it's a go.

Time to make March 27 a distant memory (actually already is)

 

[Eric B'Hymer]

Maybe i will see you out and about Shane. I drive an 03 red f-150 supercab. I am targeting ict to top along the turnpike so far. I am waiting for the morning to make my direct target but right now im leaning towards council grove. It depends on how far the warm front retreats to the north tonight. Hope to see you out there and meet you. I enjoy reading your post on here, i just dont reply often enough. Good luck tomorrow.

Eric B'Hymer

 

[Mike Peregrine]

The RUC has instinctively been the more reliable, just because it relies on the best, closer to realtime data. But anymore I take what it says with a grain of salt too. These models have been okay for mapping out synoptic features and giving us a general idea of the setup, but they've been totally sporadic on the particulars. ETA was out of position on the dryline/CF yesterday and I hadn't noticed that there would be so much of a positive tilt to that boundary until literally the second I was leaving town ... which no doubt played a serious part in how quickly those things lined out last night.

I haven't devoted any time to analysis for tomorrow and don't know if it would help much if I did. Once I get to work in the a.m. I'll start looking at RUC runs with a goal to seeing how closely they are matching the soundings ... don't have a clue about this stuff overall, though. This year is starting to be as much luck of the draw as anything.

If Jeff is right about the angle of the DL tomorrow further west (if I'm reading him right) and the weak helicity values (again, all information we are relying on ETA for) ... but let's say that is an accurate depiction of the scenario ... even if the good helicities exist in western Missouri, what can we expect to happen ... I think it would be similar to last night, where the best shear/helicity was targeted over MN/WI ... but because the CF was able to break the cap early on, and owing partly to the angle of the boundaries the storms quickly became linear. Even the ones really rotating were not serious about doing the job.

I'm guessing that tomorrow will be similar unless we can see some changes in the angle these systems are coming across this trough. Guess I'll wait and take a better look tomorrow. Haven't looked at one model yet tonight - and doubt if it will do anything for me if I did!

 

[Gabe Garfield]

The main caveat for tomorrow is the weak ambient shear, as forecast by the ETA. However, there will be a plethora of low-level boundaries tomorrow since there has been plenty of surface based convection this evening. As most of us know, these outflow boundaries can easily make a marginal tornado situation go to uber tornadic. I think that will be the case tomorrow if ample instability develops. Just my take.

Gabe

 

[Shane Adams]

Originally posted by Eric B'Hymer
Maybe i will see you out and about Shane. I drive an 03 red f-150 supercab. I am targeting ict to top along the turnpike so far. I am waiting for the morning to make my direct target but right now im leaning towards council grove. It depends on how far the warm front retreats to the north tonight. Hope to see you out there and meet you. I enjoy reading your post on here, i just dont reply often enough. Good luck tomorrow.

Eric B'Hymer

Thanks Eric. Good luck out there tomorrow.

 

[Kevin Scharfenberg]

I think the area of biggest interest will be east central Oklahoma, perhaps in the Henryetta/Eufaula/McAlester area.

Farther north, it looks like winds will veer out and be largely unidirectional as a vort max moves into Iowa a little too early in the day. The dryline/front will trail southward into south central Oklahoma. An upper level jet will be nosing out over the dryline across Oklahoma, with strong diffluence aloft. That should help keep the surface winds more backed (or, less veered) than farther north, yielding not-so-bad shear profiles (0-6km bulk shear 35-40 kts and 0-3km helicity 200-250 m2/s2). The available (still meager) moisture should show good pooling, yielding CAPEs of 2000-2500 J/kg.

This is a cursory look based on the 00Z data. I'll try to look a little more in depth in the morning.

 

[Kevin Martin]

My Target is Joplin, MO

Joplin Area, SW Missouri

Probability of Severe Thunderstorms is 56%
So with that 56% it corresponds with my charts on.........

Severe Thunderstorm Risk.
NO SEVERE RISK(NONE)
GREEN ALERT(LOW)
YELLOW ALERT(SLIGHT)
ORANGE ALERT(MODERATE)
RED ALERT(HIGH)
PINK ALERT(EXTREME)

Type of Event.
NO SHOWERS
SHOWERS
NO THUNDERSTORMS
WEAK THUNDERSTORMS
STRONG THUNDERSTORMS
SEVERE THUNDERSTORMS
HIGH RISK SEVERE THUNDERSTORMS

Thunderstorm probability is 65%.
no Thunderstorms expected
Slight Chance
Chance
Possible
Likely
Run For the Hills

Forecast Discussion.

Dewpoints in the lower 60's and temperatures in the 60's make for a Marginal unstable atmosphere today. Models indicate a very sharp dryline is in place. CAPE values are at 1000, so expect a bit of explosive developments. 850MB Low Level Jet showing 40 knots, enough to support long lived supercells. 500MB winds at 45 knots so very damaging straight line winds are a major threat. Hail value at 350 so large hail is possible. Helicity at 150, so weak tornadoes in the F0-F1 range are possible, so A Tornado Watch has been Issued by W.I.R.T.

Severe Risk: Moderate

Main Concerns: Slight Chance Damaging Winds, Large Hail, and an Isolated Tornado.

MARTIN

That would be my target.

Kevin Martin

 

[Shane Adams]

This morning's 21Z RUC shows a CAPE max in eastern OK, which I think will be key if it verifies (and the RUC has been very reliable as of late; a check of radars at 6:30am matched up well with its current 12Z precip map). As Kevin S noted yesterday, eastern OK may be the best place to be on a day like today, where (once again) most parameters are average/marginal. It would only figure that since we finally have some juicy air to work with, the windfields go to crap.

On weak or unfavorable shear type days, I am drawn to the areas of best instability. I'm pretty concerned about the lack of backed surface winds anywhere, per the 21Z RUC. Surface maps show backed winds currently, but I'm wondering if the RUC will verify on this particular parameter. With the dryline re-developing and expected (last I heard) to move towards I-35 during the day, I'd think the winds in EC/eastern OK would back in response to this. Of course, if the low currently in W Nebraska accelerates quickly we could be screwed.

So, that said, I'm eagerly-awaiting the next RUC update (to include a 0Z run). The ETA is the same run as SPC based their 06Z outlook off of, but now that the RUC will come into play on their forecast, I'm gonna predict a drop in the tornado probability map from 5 to 2% across the entire outlook area, and maybe dropped a bit further south in eastern OK to include a small bite of NE TX. Of course, if they leave the 5% in, that suggests to me that they feel the models are being too agressive with moving the LOW east through Nebraska.

Can you tell I'm not really good at analysis yet? Now I'm gonna go see if I just made a fool of myelf or not. Heading to SPC's site now....... :arrow:

 

[Eric B'Hymer]

Shane,

There may be some backed winds near the outflow boundary from this mornings convection. It is supposed to camp out near the ks-ok border. I am gonna stay close to home here in se ks and be within 40-60 miles of development hopefully. I am gonna keep an eye on the ruc and the spc and see if it verifies. I was disappointed in the mostly unidirectional wind fields aloft but things can change and i hope they do. Only time will tell.

 

[Shane Adams]

Apparently SPC felt pretty good about things. They extended the 5% to include most of eastern OK. I guess they're also anticipating backed surface flow near the OFB. Right now I'm trying to decide where to go; playing the boundary along the KS/OK border is tempting, but I'll need to see new RUC runs and get a feel for where the instability spikes will be. if we can get 1500-2000j/kg near that boundary, I'll probably go up there. But something is telling me to not ignore the dryline in eastern OK.

Be back later after some more analysis.....

 

[Shane Adams]

Just did a quick analysis (I do better with minimal effort) and we'll be heading to Bartlesville, OK around noon. Quick check of parameters show a bullseye in this area by 21Z; UVVs are stacked (non-linear fashion), RUC now breaks out precip in this area by 21Z (previous run didn't), good CAPE throughout the area through 21-0Z (1500+), and dewpoints are pooling in that same spot around 21Z.

Of course, as always, there is one fly in the ointment, and it's HUGE....winds suck. Everything from 250-700 is almost unidirectional, with marginal speed shear noted through 250-500.....we needed SSW 850 winds to provide a huge majority of our directional shear, and this latest run has them nearly due west just west of this area by 21Z. So it's a no-brainer for me now - we're playing the boundary and hoping like hell we get some serious backed surface flow.

I'm confident this area will see severe storms, and I'm hopeful we'll get some mesoscale magic and somehow get a tornado or two (seems to be happening every other day this week).

 

[Chris C Sanner]

I am going to be severely limited in chasing range today. So with that said, my prospects are not great today with me being able to only play SC and SE Oklahoma. I'll be watching the dryline and seeing what I can get out of it. If we can get some backing I'll feel decent about my chances today. If we can get some more clearing than forecast (already some breaks in the clouds here), that'll be a huge positive. Its a no-brainer for me to be out today as its so close, but I'm also liking Thursday as a great oppurtunity to chase.