3/23/09 FCST: NE, KS, OK

[Brad Nelson]

ICT forecast sounding

It isn't? Heck, the 024hr NAM forecast hodographs for ICT and HUT shows substantial low-level curvature, leading to very impressive (widespread) 0-1km SRH of 250-400j/kg across the warm sector. Yes, there is a rather deep-layer of unidirectional flow, but boundary layer directional shear is quite substantial (hence the pronounced low-level cyclonic curvature) and supportive of low-level mesocyclones. Thermodynamically speaking, the 1000-1500j/kg of surface-based CAPE isn't exactly "marginal" for a March setup, neither.

Needless to say, I'll stick to my original (albeit I'm not chasing this setup, nor any others for at least a few more weeks) target of ICT. I think there is a fair shot at a productive tornadic supercell in southcentral KS tomorrow afternoon.

Couldn't agree with you more here Nick. I was peeking at some of the forecast soundings off of Bufkit earlier today and was immediately drawn towards the late afternoon and especially the early evening soundings off the NAM for ICT. Low level shear was very impressive and the hodographs had that classic sickel shape to them. Plus, they were throwing out there almost 1300 j/kg in CAPE which would certainly be enough instability for tomorrow's setup. For chasers sake, just hope that it isn't too late in the day before things really get going.

 

[Mike Johnston]

The early RUC runs today indicate good potential for severe late this afternoon into early evening. I would initially target S Central Kansas, specifically Mt. Hope (on KS 96 halfway between Wichita and Hutchinson.) By 21z, parameters look very promising here and just to the south west - right in front of advancing dry/wind shift line, decent lapse rates along w/~58 td's will contribute to 1,000+ j/kg SB CAPE, strong low level helicities and supportive deep layer shear.

I agree with Mikey's strategy of positioning a bit upstream due to the fast storm motions.

It looks like we're on track to reach those 58 tds over this area. Satellite observations show good clearing, although surface stations seem to indicate some low level overcast.

Interesting that the early Wichita AFD seems to think the dry line and cold front will hold back a little further west, and indicates it expects the moderate risk area to be extended a bit further west. I would be out around Mt. Hope and closely monitor the surrounding surface winds and look for perhaps some kink in the dry line later this afternoon.

 

[Jim Bishop]

As far as the warm sector chase goes I like South Central Kansas the best. But I think moisture is still lacking in this setup. Looking at the WRF 850mb dewpoints you can see how the good moisture mixes out between 18z and 00z over southern and central Kansas.

I would say Central Oklahoma would be a better bet, but the pronounced capping inversion on the Norman sounding is quite stout. There will be a nice vort max that moves through Northern Oklahoma/Southern Kansas that should cool mid levels enough to initiate convection in Kansas, but I'm not so sure about Oklahoma until a bit later, probably after dark.

If moisture profiles were better I think we'd be talking about a tornado outbreak today. Instead we'll probably see a lot of low topped supercells with amazing mid level rotation, but lacking the good low leve moisture for strong low level rotation and tornadoes. I do think there will be a couple tornadoes, but hail reports will probably be much more common. If moisture were better the chances of long track tornadoes would be pretty good today.

After dark, if storms remain descrete, tornadoes will be more likely as LCLs lower.

 

[Tom Dulong]

Latest vis satlt pics showing dryline bulge in northwest OK with a few enhanced cumulus. Latest WRF/NAM runs suggest mid-level cap weaking a little sooner from this area toward south-central KS. Norman NWS morning briefing had the greatest severe weather threat mnly to the north of OKC beginning arnd 3 PM CDT...with the greatest threat 5-7 PM. This, of course, jives with the latest SPC Day 1 Outlook. OUN forecasters have some concern about the cap breaking before sunset in the OKC area. They are planning an 18Z balloon release to take a closer look.

I am planning to head north from OKC around Noon for an initial position somewhere in the area between Enid...Pratt...and Wichita by 3 pm (probably shading toward the northeast part of area due to 50 mph storm motions). However, I will be keeping an eye to the south to see if storms break out there earlier than expected.

 

[Alex Lamers]

Well, as skeptical as I was last night, I'm being pulled a bit more towards a chase. Unfortunately, it's one of those setups that all the parameters look great, but there's just something that isn't convincing me that it will be a tornado outbreak as opposed to a severe weather outbreak.

As Jim stated, the moisture concern throws tornadoes into doubt. Depending on which model you choose, the LCLs shoot up right when the clouds can clear enough for the boundary layer to mix.

Nevertheless, shear profiles look pretty favorable and therefore it's hard to completely discount the possibility of tornadoes.

The 4km NSSL WRF shows some supercells firing off between Clinton and the Wichita Mountains around 5 or 6PM and then tracking off to the northwest of OKC metro.

LCLs seem to be lower up around Enid, with less of a cap and mixed layer aloft. If I were to go out, I'd probably head up I-35 into OKC, then west on I-40. Probably up to the Watonga area.

 

[BrandonWhittington]

is it me, or has the dryline quit advancing to the east? This morning the dryline was sharpening up near the NM and TX border and advanced rapidly to the east...Now it seems to be hanging out near the OK and TX border. Clearing skies and heating is occuring along it.

Based on this, i think the severe potential could be a bit further west. I just worry about the stout cap that is in place accross Oklahoma. I will be heading to Oklahoma around Noon and Try to get to Watonga or Kingfisher. I still think there will be one or two decrete supercells in NW Oklahoma this afternoon....

 

[Jeff Snyder]

Geez, not a particularly easy chase forecast. Big cap evident on OUN and some other soundings this morning, with 90F convective temp on 12z OUN. We certainly will need some mid-level cooling since we won't see much more moistening... The strong LLJ and pressure falls overnight led to strong mechanical mixing, such that the boundary layer was already pretty well-mixed earlier this morning. This means that we'll have to depend entirely on moisture advection that doesn't look very strong across much of the C/S target area. Yesterday, dewpoints in TX mixed out into the 48-52F range, and we may see that again today. This "dry hole" will eventually advect Nward on the very strong BL winds, but hopefully it won't corrupt the OK/KS target until midnight or later.

With the warm mid-levels brought on by the system being a bit farther N than earlier forecast (note shift in 250mb and 500 mb jet axes a bit N from previous model runs), I want to hedge northward. Well, that and the fact that storm motion today should be 45-50 kts to the NE... However, I have to give some credit to the explicit-convection WRFs that are initiating storms W of OKC around 0z. Heck, even the 12z operational NAM has QPF W of OKC by 0z. I assume the models are initiating in this area because that's in close proximity to the low-level thermal axis (>80 F temps possible in extreme SW OK and adjacent portions of TX late afternoon). So, that area will probably be characterized by a warm, deeply-mixed boundary layer, perhaps deep enough (and W enough) to remove any meaningful CINH.

Regardless, shear is fine pretty much everywhere, so I won't discuss kinematics. Sure, it's not the best setup (nor is it even a "good" setup, IMO), but I'm close. More often than not, it seems that high shear, low CAPE setups don't produce much from a chaser standpoint, but it's March, so I expect high shear, low CAPE setups. Current target is in line with that of many others' - Enid to Blackwell area, hedging northward, but giving some credence to the explicit WRF runs of initiation W of OKC.

 

[Brandon Lawson]

Models have been showing a stationary dryline in the western half of Oklahoma for a few days now, I think. I'm encouraged by the Td's advecting northward into south central Kansas. If anything, perhaps the strong 850 winds will help to inhibit the surface Td's from mixing out as much. Depth of moisture should help with this as well, with the morning sounding in Norman showing moisture at or around 850mb. This may improve as the day goes on.

I laugh at myself for thinking this system would slow down a bit. Not once did any model even hint at this happening and here we are. Even still, with timing of initiation an issue, I'm glad the system came through when it did.

Will head out this afternoon and target an area between Blackwell, and Wellington to start out.

 

[Chris C Sanner]

Looking at conditions this morning, looks like we got an interesting day unfolding, although I'm not quite sure I'm believing the 15% hatched area (call me jaded from the last 10 or so that have busted over the years). There are two areas I'm watching for storm initiation this afternoon:

1)Dryline out in western Oklahoma and 2)Area of convergence from Sayre - Near Enid - Ponca City. Will probably park it near or north of I-40 with good southern options. The big thing I'm also looking at (as is everyone else) is CAPE values. We already have 1500 CAPE in far SW Oklahoma. If we don't mix out too much, we could end up near or just above 2000 this afternoon. That'd be a nice kick in the pants for any storms this afternoon.

Still waiting on the 18z OUN sounding, should be interesting to see how strong the cap is even though we're not quite in the sunshine just yet.

EDIT: Looks like we will be targeting just W. of Watonga near the big intersection to give us plenty of options for today, road options in every direction! I will be using Twitpic and Twitter to keep folks updated on our progress.

http://www.twitter.com/chrissnr

 

[Tim Vasquez]

The fine details in the upper-air fields from yesterday's WRF to today's WRF look quite a bit different and rather than putting Oklahoma in the wake of a well-defined short wave trough it puts the state in advance of a more weakly-defined one. I certainly don't see any problems with initiation today.

Tim

 

[William Reid]

I'm sitting this one out, and trying to figure out where I would want to be if I were chasing. A look at the surface and upper air forecast maps for 21Z to 00Z today say "get thee to Huskerland", in my opinion. I do tend to keep things simple, however, and a position just in front of the Big Red "L" is often times the place to be for tornadoes. I am impressed with the forecast upper-level diffluence over much of eastern Nebraska later this afternoon---the maps just have that "I'm gonna make tornadoes today" look to them.

Farther south, the positives for daytime tornado-making diminish somewhat. As has been mentioned, the strong cap and moisture quality are problematic. The best chance for big tornadoes may be in OK and KS, but not until after sunset.

I like Hwy 281 from Grand Island to O'Neill at this point in time. It is a tough call as to whether to play the north end or south end, though. I'll favor O'Neill, for now.

Bill Reid

 

[Tim Vasquez]

It's interesting that there's a bit of a cold pool that's developed in central Oklahoma due to wet-bulbing from drizzle and light rain. Here at my place east of Norman it's 62 and everything is completely wet outside (not just drops but a continuous film of water). Isotherm analysis shows the edge of this cold pool from ADM-CHK-GOK(Guthrie)-TUL . It will be interesting to see if this acquires any further definition as the afternoon wears on (maybe not, given the weak forcing), but it's something worth pointing out.

Tim

 

[Chris Nuttall]

MOD NOTE: Since the event has now begun, and there is an active NOW thread, I'm closing this FCST.