4/9/09 FCST: TX / OK / KS / AR / MO

[Greg Blumberg]

This is the first time I've really looked at this setup today, so I don't really have too much to compare to in terms of past model runs. Should have been watching this a bit closer.

Judging from the concerns about moisture, I would pay attention to the high that is currently dominating the Gulf. Both the NAM and GFS currently are indicating that the high will move eastward around 06z today and return some sort of southerly flow to the Texas coast. Only after that can we answer our big question about the quality of the moisture further south of the buoys.

Something I noticed on the models was the existence of a sub-tropical jet that I think is merging with the polar one. I'm not too familiar with synoptic meteorology, but will that slow down the system, speed it up, or do nothing? My guess is that it'll speed it up.

I also started looking at the WRF today and it's indicating the moisture surge as well, but everything seems to be in SE OK i.e. the dryline around 0z. There's no way I'm going down there.

 

[Brandon Ivey]

I think I am going to pick the northern play. Not going to get into all the details and parameters, as many have already pointed them out, and they are subject to change anyway. If I had to go with a target off the latest models, I would say highway 166 in Kansas between Ark City and Coffeyville.

Good luck to all those chasing down in SE Oklahoma in the jungle. I've been there, done that, not planning to do it again anytime soon! If that was the only target though, I would be there, chainsaw in hand!

 

[Jeff Snyder]

Oy, it's certainly not slowing down. The 18z and 00z NAM runs are a bit faster / farther east compared to some previous runs. Shear looks pretty good, though previous forecast soundings weren't showing much shear in the 2-6 km layer (i.e. through the bulk of most storms that may occur). In other words, because of the veered 850mb flow, low-level shear is good, but there isn't too much above that, even though the net 0-6 km shear is sufficient for supercells (40-50+ kts). If things don't shift back westward, I'll have to set my target to the area immediately east of the low (in a sort of bent-back area N of the larger-scale dryline bulge). The terrain in extreme NE OK, SE KS, and far SW MO isn't too bad -- certainly much better than the area along the OK/AR border (which isn't too far E of the forecast dryline position at 00z from tonight's NAM). That said, I do like the shear and forecast hodographs farther south (i.e. nearer I40) better... Check out the forecast sounding valid for FSM at 00z --> http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=048&STATIONID=kfsm

Now, compare that to the 00z JLN (Joplin, MO, I hope) sounding -> http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=048&STATIONID=kjln ... Note how the hodo has a more S-shape to it. Yuck. However, I'm not sure it's entirely feasible to chase E of MLC and into northwestern... The area E of Hwy 69 from Atoka to Vinita is tough going IIRC, and the situation improves once you get N of Vinita (into southwestern MO north of Hwy 60 (which runs WSW-ENE south of I44).

 

[Mikey Gribble]

After glancing over the 00Z NAM I still clearly favor the I40 area in Oklahoma, but with it coming into line with the GFS on the dryline placement in far eastern Oklahoma, we are talking about chasing into western Arkansas if we target down there. That is a serious negative against that target. If the dryline were going to be back to the west a little ways so storms would stay out of the mountains then I'd chase the I40 area for sure, but man I really don't want to get in the hills and trees. This is going to be a tough call. In addition to that the 00Z NAM fell into line with the GFS on veering 850mb winds more along I40, which I hate. Yeah I know it helps spike SRH, but things never go well when 850mb winds veer badly.

This is going to be a tough one to figure out. I can target up here at the surface low and keep it close to home or potentially chase in the jungle down south where I think there will be a much better storm. I can already tell I'm going to be torn when it comes down to decision time on where to go Thursday morning. I think the I40 area really has a much better chance of producing some quality tornadoes, but that dryline is so far east. I'd probably be in Fayetville by 8pm (only half joking). The hodographs look really nice down there (especially relative to the northern target), moisture will be better, the shear vector is normal to the boundary and there continue to be indications that a discrete storm or two will form in the I40 area. All the composite indices spike right there too. I didn't even look at them in the 00Z run, but 3km EHI was up to 7 down there on the 12Z run.

I'm going to start paying a little more attention to the northern target so I can keep my options open, but the only reason I will chase up north if I do is because chasing in the I40 area just isn't going to work out. I've never seen the terrain near I40 and the Arkansas border, but I'm betting it's not good, because I have been to Faetville and Beaver Lake and that's Ozarks country with hills and trees.

The 00Z backed off on precip a lot too, which doesn't mean much to me. The NAM and GFS normally do a poor job with precip IMO.

 

[Chris Wilburn]

Jeff you are spot on with the extreme NE OK area as far as chaseable storms. I live in Miami (30 miles from Vinita) and anything just east of Highway 69 and north of Vinita is definitely chaseable. The problem you run into chasing just east of Vinita and slightly SE of Vinita is you start running into Grand Lake and chase stuff into extreme SW MO and NW AR which is not good. Basically anywhere north of Vinita into Ottawa, Nowata and Craig counties are fine. Of course anywhere in SE KS is chaseable and SW MO isn't bad esp. if you stay north of Highway 60 and esp. north of Joplin.

Back to the forecasting part of the discussion. The NAM has definitely sped things up and is favoring an extreme eastern OK into western AR setup. Nothing needs to be said about the bad terrain in AR and eastern OK so I will not rehash that. I am targeting the before mentioned area of near Vinita and slightly northeast of there if the NAM verifies. I do like the 60 dews and good low level shear, but the problem that Jeff mentioned about the lack of shear between 850mb and 500mb is a concern. Like Mikey has mentioned several times I am also not a fan of veered 850mb winds. Instability, moisture and shear look pretty nice for this area. I think a few tornadoes are possible, but I would like to see the 850mb winds back more. Actually more than that I wish things would slow down!

Forecast sounding for Grove, OK (kgmj) on wxcaster.com looks pretty good. Valid 00z shows the following: -5 LI, 3 EHI, near 300 0-1 SRH and just over 300 SRH 0-3 SRH. It looks like the CAP breaks down rapidly between 21z and 00z in this location. CAPE 1,700 and LCL around 500 also on this sounding. I do think parameters look better around McAlester over to Ft. Smith so that may be another play as well, but I will take the play that may not be quite as good and be able to have some decent terrain.

 

[Jim Bishop]

I like the area just east of the surface low over extreme northeast Oklahoma/Southeast Kansas. Upper level forcing from the strong vort max ejecting into the area late in the afternoon/early evening with the associated height falls and cold temps aloft will be more than sufficient to break the cap by late in the afternoon/early in the evening.

Storms (supercells) should form along the well defined dryline first over Southeast Kansas/Northeat Oklahoma near the warm front where 850mb temps will be cooler than further south. By the evening storms should form along the dryline further south over Eastern Oklahoma when the cap finally breaks not too long before dark. But the storm mode further south over Eastern OKlahoma will be more mixed with veered 850mb winds.

I question the quality of the low level moisture return. The highest dewpoints from the source region in the southwestern GOM is near 60F thanks to high pressure that is just now exiting the region after wiping the Gulf clean of quality moisture.

The latest WRF model isn't as aggressive with moisture return as last night's run, and i think mid 50s dewpoints over Eastern Oklahoma and far Southeastern Kansas is reasonable. Though I would be concerned about more of that being mixed out throughout the day given the very warm and dry elevated mixed layer forecast to move into the region throughout much of the day (thanks to west-southwesterly 850mb flow midday).

Even with the moisture concerns considered, 500mb temperatures by early in the evening over southeastern kansas/northeastern OK will be around -18 to -20C. Low to mid 50s dewpoints and marginal 850mb dewpoints will support SB CAPE around 1000j/kg.

The backed low level flow and 850mb flow near the warm front will enhance 0-1km helicity values, increasing the tornado potential.

All things considered I think there will be a small corridor with tornadic supercells tomorrow late in the afternoon/early evening near the KS/OK border over eastern KS/OK. Further south the show will start later, but the veered 850mb winds will make for more of a mixed storm mode, not necessarily all supercells and decrease the tornado potential.

Edit: The latest GFS does not veer the 850mb winds as much during the day over eastern Oklahoma, and backs them to southerly by the evening. Should this verify tornadic supcells would be possible all along the dryline down into the I-40 corridor over Eastern Oklahoma into western Arkansas, not just near the triple point. But I still think the best region is near the ks/ok border.

 

[Chris Wilburn]

I like the area from extreme SE KS into extreme NE OK like Jim mentioned. I am hoping to target near a Vinita to Oswego line and latch on to a storm moving northeast from there into favorable terrain and road network. Moisture and instability are sufficient, however, I do like the backing (out of the south mostly) of the 850mb winds forecasted in this area as opposed to the south. Also, I think just east of the surface low that storms will also fire earlier over this area. Forecast sounding in the area show the CAP beginning to erode in the late afternoon to early evening between 21z and 00z due to increasing height falls and fairly cold 500mb temps. Large hail will also be a big threat along with the chance for a few tornadoes. Moisture depth at 850mb isn't too bad at near 12C. At least it isn't real shallow at this depth.

I still wish the dryline would slow down, however, since it has been consistent the last few runs it probably isn't. Also, as Jim mentioned, if the 850mb winds begin to back towards early evening there is going to be a real threat of tornadoes early evening/after dark for extreme SE OK, western and northern AR, and southern MO as moisture continues to increase while temps. decrease leading to a lower LCL height. I am sure some fine details will change in the next 24 hours, but probably not a whole lot. Moisture is the main thing at this time of course. If we can actually get 58-60 td's with a some moisture depth things should be ok.
Rapid moisture should begin surging north later this evening into overnight and right now there are mid 50 tds. near Galveston with near 40 td's creeping up towards the Dallas area.

 

[Mike Umscheid]

Think West

For my thoughts on tomorrow, please see my blog post:
http://www.underthemeso.com/blog/?p=549

 

[Mikey Gribble]

I have my forecasts on my blog too. Read the last two posts though because they are both from this morning. Here is the link http://loadedgunchasing.com/blog1/

I have decided to target the warm front over southeast Kansas. I pretty much agree with SPC's 1730 outlook probability map. I expect a higher concentration of severe along the surface low and front (obviously), but the potential (especially on the tornadoes) is higher farther south in the I40 area.
I still favor I40, but there are several things that have convinced me to chase the KS-OK border instead. First of all I'm scared of the veering 850 winds along I40. I have said it a thousand times, but I hate veering 850 winds. It never goes well and every time I get suckered in to chasing it, as soon as the day is done with no tornado I turn to Ryan and say "WTF is wrong with me. We know better than to chase this ****" If 850 can stay backed to some degree, like the gfs is showing, then I wouldn't rule out a strong tornado with any discrete storm in the 00Z-03Z time frame. SPC also mentioned LCL's as one of the issues along I40 that made it a conditional threat. The forecast soundings have been showing ML LCL's around 1200m for a couple days now. I honestly don't think LCL's will be a problem, especially later in the evening. SPC also mentioned storm mode as an issue. I don't know why that would be a problem with limited convection on all the model runs and a shear vector that's normal to the boundary. I would think discrete supercells would be the preferred mode for at least the first couple hours. And finally one of the main reasons I'm staying away from the I40 target and chasing the warm front is because the terrain and road networks SUCK along I40 and the OK-Arkansas border. With storm motions aproaching 40kts, that dog just ain't gonna hunt.

As far as the surface low/warm front target goes I want to position myself just south of the windshift. I think there is clearly a higher probability of tornadoes up there relative to the southern target, but it is lacking the potential to produce strong tornadoes which the southern target has. The warm front is only a 2 hour drive for me too, which beats the hell out of a 7 hour drive to chase in Arkansas.

I hate the uncertainty of these early season chases. You have setups that look good. There are always a few problems, but you think they should produce and then for no apparent reason they bust. It's always like that until you get into May and the first part of June when those same kind of days work out well instead of going bad. There's nothing we can do about that, but the combination of unchaseable terrain, high bust potential and veering 850's is keeping me north. My mind is made up.
Here is a link to my blog again and the last two posts are from today http://loadedgunchasing.com/blog1/

 

[Michael O'Keeffe]

I like everyone else am really looking at the warm front for the best chance at tornadoes, though I don't really have much to add as most of you got everything down, here is the dewpoint model at 6z tonight from the RUC and the 6z dewpoint model from the 12z NAM today.

RUC
http://www.rap.ucar.edu/weather/model/ruc12hr_sfc_dewp.gif

NAM
http://www.rap.ucar.edu/weather/model/eta12hr_sfc_dewp.gif

Notice the difference and the RUC model is not impossible as 60F dews are now starting to show up on the coast. If this does happen than the possibility for strong tornadoes all along the dryline including near the warm front will increase dramatically.

 

[Darren Stephens]

This one looks like a classic triple point setup but the terrain is going to be horrible. I would initially try to target the Hwy 69 and Hwy 412 jct. around early afternoon and shift your position once thing started to fire.

 

[David Toner]

I agree about a "classic triple point" but its certainly early in the season with less than "prime" ingredients, but its the first show for us so we'll target the warm front in southern Kansas or North East Oklahoma and be flexible.

 

[CZandbergen]

It looks like my wish may have come true. Latest NAM run looks to be slowing down the dry line just a bit. Still looking at the data, but Baxter Springs KS is looking like a good place to be sitting late afternoon tomorrow.

 

[Jeff Snyder]

I'm not sure about this one. The 00z NAM has the mid-level and surface lows farther south compared to the 12z NAM. The vort max associated with the 500mb trough/low moves from the eastern TX PH and far W OK at 18z, to far E OK by 00z. As such, the strongest DPVA is moving into western AR and nearing southwestern MO by 00z. With the southward shift, it looks like the warm front play may stay along the OK/KS border (or perhaps clip the southeastern-most Kansas county) in a region of only 25-30 kt southwesterly or southerly 500mb flow on the southeast and east side of the mid-level low. The better mid-level flow is forecast to be quite a bit farther south and southeast; I'm awaiting forecast soundings from the 00z NAM to help visualize the forecast vertical wind profiles / hodographs... At least the very backed low-level flow will act to increase deep-layer beyond what I would normally expect for only 25-35 kt 500 mb flow.

Meteorologically, I'd like to be in the Tahlequah, OK, to Bentonville, AR, by 00z. Unfortunately, from a look at Google Maps terrain and satellite imagery, that area looks pretty much unchaseable. As such, I'll play the area next to the sfc low as long as the 50F isodrosotherm can get up that far to the NW. If the 00z NAM is right, I'll probably start somewhere between Pawhuska, OK, and Caney, KS, in the "bent back" region. I'm a little concerned about the width of the instability corridor, as it looks like the surface temps warm from <60 F to the 60-70 F range between 18z and 00z in this area. In addition, current observations show 60-62 F tds along the TX Gulf coast. As such, with only 10-20 kt sfc winds through the night (and veered 850 mb flow), I really can't buy the NAM's forecast of >60 F Tds pretty much everywhere east of the dryline as far north as extreme southeastern KS by 00z... The cooler sfc temps will help keep LCLs relatively low up there, and the cool mid-level temps help ensure relatively steep mid-level lapse rates.

 

[afischer]

I'm likewise not real happy with the southward shift from the latest model guidance given the poor chase territory over much of northeast OK. I think the potential for a pseudo cold core play looks better in some regards on the 00Z NAM, as previous runs had 35-55 kt 500mb flow (southeast of the mid-level low) overspreading the surface low and adjacent warm front. The 25-35 kt 500mb flow forecast off the 00Z run looks better for keeping storm motions slower (lessening the risk of them quickly becoming elevated), and is in the range consistent with a lot of other cold core tornado events (particularly those tied directly to the cool side of a baroclinic boundary). I'm a little leary of sticking close to the surface low tomorrow though, given the progressive nature of the low and strong low-level cold advection forecast in its wake. I'm also not sure how "tornado friendly" the cool side of the effective warm front will be, given the rather late arrival of the substantial low-level moisture (if it in fact arrives as forecast) and 700-500mb temperatures that are not especially impressive for an early April cold core event. My initial hunch is to play the northern end of the warm sector, east of the low a bit (say, the far eastern KS-OK border), and hope something goes up on the northern sections of the dryline and gets its act together in far northeast OK or far southeast KS before outrunning the narrow instability axis. It is certainly possible that a better cold core play might evolve farther west, tied to the surface low/warm front intersection, and surface obs and visible satellite later on tomorrow will help with figuring that out. If we can't get upper 50s dews up toward the KS-OK border before dark, the sfc low target (w/ the coldest temps aloft and strong PVA) may be the only viable option.