5/1/08 FCST: KS/MO/OK/AR/TX/NE/IA

[Jason Montano]

Just a quick look at the 0z eta forecast sounding, NE OK looks really nice. Around B'Ville the LI: is -8.7, CAPE: 3871 j/kg, 0-3km SRH: 312.9, SC potential: 91.7%, CINH: -5.2 j/kg, LCL: 563m.

If that "monster" (kidding) cap of -5.2 j/kg can be broken the ingredients are def. present for some monster Supercells in this area. Will be waiting to see how the other models handle this setup in the coming days. Also of note is the Eta has precip breaking out around the OK/KS border near B'ville by 0z.

 

[Mike Hollingshead]

At 18z the sfc low is near ICT. The cold front is crashing se and that low "splits" lifting ne and dropping sw. Tendancy to the south is going to be to want to veer the sfc/low levels. Did I say it was new? No, I just noticed it's process from 18z-6z.

What's crashing? The cold front dryline intersection is in southern Kansas at 00Z and by 06Z it's overtaking the dryline in central Oklahoma. Unless you are planning on chasing until 3AM I don't see what the issue is. The models have been showing the cold front overtaking the dryline Thursday night for several runs now. It's nothing new. Hence my post earlier in this thread when somebody asked why SPC highlighted the area all the way down to southern Oklahoma and I said because a squall line would probably form along the cold front after dark.
I just think it's funny how people favor their backyard and then get pissed when somebody disagrees with it. I don't care what anybody else says in their forecast so I don't know why they'd care about what I say in mine.
Then I get some ignorant comment on here asking if I had a model that "predicted the strength of tornadoes". Really??? Obviously you don't know how to forecast and haven't chased very long because with a little experience and forecast knowledge it's really not that hard to recognize a setup that supports strong tornadoes. How do you think any forecast office makes a distinction between a low end tornado threat and a setup that can support strong tornadoes??? Do they have a model that "predicts tornado strenght"? No. It's called forecasting. You should try it some time. BTW this comment is just directed to the person who made that comment earlier.
I'm not saying that we'll get strong tornadoes, but I am saying that if the GFS verifies we will certainly have the potential for strong tornadoes. If you don't want to believe me on that then look at the forecast composite indices for Thursday. Those formulas are written by SPC forecasters among others. They must not know what they're doing either.
Everybody chase north and I'll chase south. That's just fine with me. I would rather not have the traffic down here anyways.

 

[Mikey Gribble]

The precip. breaking out in every run is definitely comforting after the problems we've had with the cap lately.

Mike said...
"At 18z the sfc low is near ICT. The cold front is crashing se and that low "splits" lifting ne and dropping sw. Tendancy to the south is going to be to want to veer the sfc/low levels. Did I say it was new? No, I just noticed it's process from 18z-6z."

I'm just worried about the 22Z-02Z time frame so the cold front "crashing SE from midnight to 3AM doesn't worry me a whole lot.

Hey Jason where are you getting forecast soundings going out that far. All I can get is out to 48 hours.

 

[Jason Montano]

...Hey Jason where are you getting forecast soundings going out that far. All I can get is out to 48 hours.

http://www.wxcaster.com/etaskewts.htm

 

[Mike Hollingshead]

The precip. breaking out in every run is definitely comforting after the problems we've had with the cap lately.

Mike said...
"At 18z the sfc low is near ICT. The cold front is crashing se and that low "splits" lifting ne and dropping sw. Tendancy to the south is going to be to want to veer the sfc/low levels. Did I say it was new? No, I just noticed it's process from 18z-6z."

I'm just worried about the 22Z-02Z time frame so the cold front "crashing SE from midnight to 3AM doesn't worry me a whole lot.

Hey Jason where are you getting forecast soundings going out that far. All I can get is out to 48 hours.

Yeah it wouldn't me either, except it seems that evolution leans towards the southern sfc low and low levels losing their "grip" starting way earlier in the day. But maybe it won't happen so much like that, and enough of an area will stay backed closer to how the model says. And my thoughts have zero to do with whose yard its in. I hope it all ends up like the ECMWF and I can play between the two current yards.

 

[Van DeWald]

One thing that worries me about the northern target will be the extent of the stratus that will develop Thursday (especially as depicted by the Nam), and how much of it can break by late afternoon. That would certainly favor the southeast Kansas/northeast Oklahoma target. Nam is suggesting that it could break up here by 21z-00Z, but if not, the whole setup could be augered up north. Have to admit now, parameters are looking much better south, with the southern double low structure.

Van

 

[Dustin Wilcox]

Couple of pretty forecast soundings from the southern target...

NAM
http://68.226.77.253/skewts/NAM-test/072/SKT_NAM__KCUH.png

GFS
http://68.226.77.253/skewts/GFS-test/072/SKT_GFS__KCUH.png

 

[mark plate]

At 18z the sfc low is near ICT. The cold front is crashing se and that low "splits" lifting ne and dropping sw. Tendancy to the south is going to be to want to veer the sfc/low levels. Did I say it was new? No, I just noticed it's process from 18z-6z.

I agree with you that if the WRF/NAM verifies, the setup down here in Oklahoma is not at all favorable for tornadoes. Have seen these "crashing" as you call them or "sagging" as I call them fronts many times over the years and they just don't tend to produce much around here ahead of the front. Whenever I see the "saggy" look in the models, I tend to downplay the situation.

The good news is that the WRF/NAM is many times way off target, and the ECMWF and UKMET both look more favorable for this area. Hopefully the dryline is slower than the ECMWF though. We'll see.

Overall, a more northern target definitely looks best to me at this point in time.

 

[afischer]

The new ECMWF is looking relatively nice from a pattern recognition standpoint, showing excellent continuity with the past couple of runs of that model... and it actually continues to slightly slow the system a tad. This new 00Z run has the pacific front/dryline SLN-ICT-OKC at 00Z Fri. The new GFS looks wretched, with pressure rises slinging a cold front through the area. It will be interesting to see what kind of moisture we have to work with by Thurs afternoon & evening given at least 36 hours of return flow straight out of the western Gulf. The high-res models indicate mean boundary layer dewpoints of 14-17C shaping up by Thurs afternoon. Even if this is a little on the rambunctious side, hopefully we will still be in decent shape given the dynamic cooling/lift from the upper system ends up being well-timed across the initiating boundary.

Edit: Just got a look at the high-res version of the ECMWF, and it has the surface boundary farther east and more banana-ish. I don't care for the looks of it, with the strong cyclonic flow mostly behind the boundary. Hmmm...

 

[Brian McKibben]

After looking at the 12z WRF it looks like it is coming into agreement with the GFS. The WRF has moved everything a little further east. The dryline makes a nice push around 00z but it quickly gets overtaken by the cold front.

I think a good target would be somewhere north of Tulsa. The shear looks to be pretty good and there is a better chance of breaking the cap near KS/OK border.

 

[George Limpert]

I'm certainly intrigued by SE KS/SW MO/NE OK around 00Z Friday, but I have some serious doubts about convective initiation occurring prior to 00Z. The GFS and NAM continue to show a rapid erosion of the cap between 18Z and 00Z and I'm not sold on it happening yet. As per the 12Z GFS, MLCINH weakens from -271 J/kg at 18Z to -11 J/kg at 00Z. I'm not believing the rapid weakening of the cap and the 5 degrees C decrease in 700 mb temperature. I do think convection will occur, but I'm certainly not sold on storms developing until the cold front catches up to the dryline.

 

[mark plate]

The 12Z runs continue to show significant discrepancies between the normally superior UKMET/ECMWF solutions and the U.S. based GFS/WRF-NAM solutions. The ECMWF and UKMET both continue to indicate a much deeper surface cyclone over the central plains with the UKMET being slower and about a state further south than the ECMWF with a deep surface cyclone in central Kansas at 00Z Friday. HPC prefers the ECMWF and UKMET as do I based on past experience.

The slower/southern solution of the UKMET keeps the dryline back closer to I-35 by 00Z instead of east of Tulsa like the ECMWF. Neither model breaks out any convection in the warm sector in Kansas and Oklahoma prior to 00Z. The quality of moisture is also in great doubt with the ECMWF backing off on dewpoints east of the dryline...now showing just above 60 at 00Z Friday. Current observational trends suggest this is likely closer to reality than the GFS and the WRF/NAM as has been the case with nearly every event this season. All this suggests that any storms prior to 00Z will likely remain very isolated and be LPish in nature.

The chances for significant severe increases markedly as the evening wears on east of the dryline across SE KS/SW MO/ERN OK with an eventual evolution into a squall line likely by 06Z.

 

[Marcus Opitz]

Dewpoint in SGF is currently 29F, from what the local forecast discussion is saying, the GOM is not as juicy as it normally is....

I think moisture will be the limiting factor and may keep the CAP nicely in place. I am not sure the 30-40 mph winds will be able to pump that much moisture that far north.

Tommarow will be very conditional indeed.

 

[Mike Hollingshead]

Gulf bouys show mid 60 to low 70 dews in the southern portions. The northerly flow turns around tonight and there's really good return flow for at least 36 hours before 7pm Thursday.

http://www.rap.ucar.edu/weather/mod...25_wnd&hours=hr36hr42hr12hr48hr18hr60hr24hr30


I don't think moisture will be too big of an issue.

I hope the UKMET or ECMWF are a lot closer on this. If the UKMET is right I'll be heading towards se KS Thursday. If the NAM or GFS are onto things, I don't know that it will be worth it or not.

I can't see what it does with the sfc winds where I'm looking at it, but the 850 500 cross over looks like it would be pretty sick in se KS. The sfc low looks better on there and I would guess they'd be a little backed.

 

[Mikey Gribble]

I just glanced over the NAM and GFS, but it looks like 850mb winds are veering a little more than in previous runs (especially with the GFS). I haven't checked out the European models yet. Obviously I need to. If 850mb winds do in fact veer badly that could be serious trouble for the tornado potential. I think it's probably OK if 850mb just veers a little as long as 925mb and surface winds stay backed ahead of the dryline, but the tendency for low-level winds to veer as you approach the cold front intersection is making me extremely nervous.
It looks like the GFS is falling in line with the NAM on the location of the best low-level shear (like it did a couple weeks ago), which means I will likely be pushing my target farther South to somewhere northeast of OKC.