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

[Brian Emfinger]

Just glancing at a few things... If the NAM dews verify then NE OK/SE KS look really nice. Parsons, KS and Tulsa are nearly the same at 0z Fri with about a 1.5 cap, 25 CINH, 2500 CAPE, Helicity 400, and LI -6. I am definitely not encouraged by the current dews in Texas and the GOM. NAM has 65/66 dews (Oz Fri) for Parsons/Tulsa but the 65 ISOD. is currently closer to Cancun than Houston...not good. I can see 60ish dews making it up there but probably not 65. Looking at the 45-48hr Oz NAM fcst Skew-T at Tulsa (Earls Model Skew-T Page) it erodes the cap from 5.1 to 1.0 over those 3 hours (and from 8.1 at 42hrs/18z)....and if the forecasted dews can't be reached then that quick erosion seems unlikely. Looking at the 6z the NAM still has 66 deg dews at Tulsa by 18z tomorrow and 62 deg dews by 0z tonight. 60 deg dews aren't currently found till S Coastal Texas. If we can somehow get the dews to verify then I think storms are more likely than not in KS/OK but if they don't then it will likely be a nighttime mostly elevated event.

edit: I am continuing to try and temper my enthusiasm for this event (in case it bust) but its certainly becoming hard.

Here is the 12z NAM 36hr/0zFri sounding for Tulsa (it wouldnt save the background)

 

[Michael O'Keeffe]

Looking at the latest surface obs I am quite impressed. 50F dews are now in S Oklahoma with low 60s now on the TX coast. The winds are screaming out of the south here and so I am becoming more confident in moisture return and our possibilty of daytime supercells with possible tornadoes.

 

[Chris Gullikson]

I have been considering the northern target for a few days now and while I am not liking the lack of helicity shown of the WRF I believe there will be plenty of low level shear up against the surface low that the model is not seeing. Would like to see some precip across eastern NE and IA in the morning to create a boundary but it doesn't appear like that will happen.

Also, besides the mentioned veered 850 flow, the upper level support is slow to arrive and with an already capped and possibly mixed boundary layer, it does look like a nocturnal event further south along the dryline.

 

[Scott Weberpal]

I like the northern target as well, but it's a northern target which no one has mentioned yet. N. IL looks like it's in a great position with the warm front draped across the area, and attenant strong deep layer shear. Veered H85 flow further south should help moisture pooling along the front, yielding at least moderat SBCAPE. Also appears per the 12z WRF that a well timed wave will be moving across IL mid-afternoon. I can think of a few scenarios (including 4-20-04, and another day in either late april or early may 03) where the sfc low was in W. IA or E. NE, and the warm front lit up with tornadic supercells in IL. I think there are more question marks along the dryline than there are along the warm front in IL. Not to mention, the WRF breaks out a nice isolated "blob" across N. IL by 00z. At this point, I'll even take a weak spinup over a blue-sky bust if the cap holds along the DL.

 

[Randy Langton]

I'm sitting in my office in Houston and the good news is that in the last hour the nice warm, MOIST, air has returned and is now visible. I hope this trend continues northward...

 

[Chris Gullikson]

I like the northern target as well, but it's a northern target which no one has mentioned yet. N. IL looks like it's in a great position with the warm front draped across the area, and attenant strong deep layer shear.

That has been on the back of my mind as well. Makes for a much shorter drive for us as well.

Looked at some forecast soundings for NW IL, nice directional shear and curved hodo. Looks pretty good if the WF holds down there and we can get some convergence along it.

 

[Brandon Sullivan]

I have been monitoring the Northern IL setup too, as I dont find it feasible to get to KS/MO before dark, with not getting out of school until 3. And what is the point of driving all that way to chase in the dark..

The things I do like about Northern IL..
-Nice DP's
-Good Instability ~1500 J/KG
-STP's and Sup Composites
-Precip (LOL)
-Less CINH

Things Not So Impressive
-Not the most impressive Shear/Helicty

I'm not sure im terribly confident in the area though, since SPC hasn't even touched it. But I try not to let that affect me.

Have to see what SWODY2 Brings, but this target would ultimately be the best solution for me.

Good luck to all who do go out!

 

[Brian McKibben]

I am concerned that the cap is going to be too strong for storm south of the KS/OK border. The northern target near Topeka/KS City appears to be favorable for at least storm development. Although the moisture is meager up there I bet some spots will still see low 60 Tds.

The 12z WRF doesn't break out much precip except for near the triple point. I find that the triple point is frequently a good place to chase, but if storms can break out down near Parsons and tap into that moisture it could get insane.

 

[Mike Hollingshead]

I still don't think moisture is going to be much of an issue tomorrow, other than maybe some 850 dry air wanting to mix down. 12z GFS doesn't veer the 850 bad at all now. The ECMWF and UKMET both are still even nicer with that. They all have very strong return flow below that level. I'm just thinking there's going to be a wall of the good stuff screaming north overnight.

Yeah, buoy 42002 in the western gulf still only has a 60 TD. Same at 42001. 42055 is already back up to 68 though. I'm just guessing that good stuff ain't all that far south of the 42002 and 42001 buoys.

http://www.rap.ucar.edu/weather/model/ruc12hr_925_wnd.gif
With that kind of flow off the deck by 10pm, it's just not going to take it long to get north.

And hell all day up to then it's already starting to tug on it.
http://www.rap.ucar.edu/weather/model/displayMod.php?var=ruc_925_wnd&hours=hr03hr06hr09hr12

Then you have all night, with things ramping up even harder, plus the day tomorrow.

I am liking the temp maps...
http://www.rap.ucar.edu/weather/model/eta36hr_sfc_temp.gif

Any cold air is well west of the dryline/moist axis. Stronger 500mb winds coming over the dryline at 7pm. Looking great to me for a couple isolated supercells before dark in se KS, probably not many.

 

[George Limpert]

I'm not as confident about the moisture return as some of you are. I still strongly believe models are overdoing the moisture return. Indeed, the RUC already is overdoing the moisture in the Gulf.

I've plotted 18Z obs and 17ZF001 RUC dewpoints in the Gulf. Buoy 42002 reported a dewpoint of 60 but the 17ZF001 RUC dewpoint is around 65. I've posted the comparison at http://weather.missouri.edu/People/limpert/18ZOBS_RUC.gif. It looks to me like dewpoints are too high in the RUC over a good portion of the northwest Gulf.

 

[Andrew Ryan]

I would be surprised if we didn't have 60+ Td by tomorrow afternoon at the KS/OK border. Right now Tds are around 50 and steadily increasing. The winds are also increasing rapidly now from the south where some 60 Tds are just coming onto the TX shore.

http://hoot.metr.ou.edu/surface/raw_obs/spl

 

[Mike Hollingshead]

I'm not as confident about the moisture return as some of you are. I still strongly believe models are overdoing the moisture return. Indeed, the RUC already is overdoing the moisture in the Gulf.

I've plotted 18Z obs and 17ZF001 RUC dewpoints in the Gulf. Buoy 42002 reported a dewpoint of 60 but the 17ZF001 RUC dewpoint is around 65. I've posted the comparison at http://weather.missouri.edu/People/limpert/18ZOBS_RUC.gif. It looks to me like dewpoints are too high in the RUC over a good portion of the northwest Gulf.

It'd be most interesting to plot current obs compared to the ruc 3 hours earlier(or even to the NAM/GFS which would probably be more useful). If it's only 3 hours slower to reality, not a big deal to me. And as the obs vs ruc looks on there, with the big missing gaps out in the ocean, it doesn't look that crazy off, and quite possibly just a couple hours quicker than reality. All that matters to me is knowing where the good stuff is, and it looks like it's between 42002 and 42055 somewhere. Then knowing how strong the prog'd return is through the night into tomorrow and where that flow is. Both NAM and GFS only showing mid-60 dews into se KS and I just don't see why this would be hard to do. And there are some differences between this return flow with veering 850s and that bust last time. Behind that morning precip the lower level flow was rather weak and the 850 dry nose was really pronounced. I think we'll have much better low level feed under a weaker sort of 850 veering. If not I guess I'll get sun burned tomorrow, as I plan on driving past the northern target this go around.

 

[Scott Lincoln]

I think the pivotal point for moisture return is going to be this evening, a few hours before dark. If the dewpoints really dont start increasing faster as the 850mb jet kicks in and becomes more southerly, then thats when I'll get concerned for sure.

As far as the cap goes... I just dont see there being a high chance of the cap breaking in southeast Kansas or northeast Oklahoma. The 700mb flow is almost parallel to the isotherms there, but compare that to southeast Nebraska into northeast Kansas, where the winds are perpendicular to the isotherms. There is much more rapid cooling, and better upper air support, for large scale ascent closer to the main low in my opinion.

 

[George Limpert]

It'd be most interesting to plot current obs compared to the ruc 3 hours earlier(or even to the NAM/GFS which would probably be more useful). If it's only 3 hours slower to reality, not a big deal to me. And as the obs vs ruc looks on there, with the big missing gaps out in the ocean, it doesn't look that crazy off, and quite possibly just a couple hours quicker than reality. All that matters to me is knowing where the good stuff is, and it looks like it's between 42002 and 42055 somewhere. Then knowing how strong the prog'd return is through the night into tomorrow and where that flow is. Both NAM and GFS only showing mid-60 dews into se KS and I just don't see why this would be hard to do. And there are some differences between this return flow with veering 850s and that bust last time. Behind that morning precip the lower level flow was rather weak and the 850 dry nose was really pronounced. I think we'll have much better low level feed under a weaker sort of 850 veering. If not I guess I'll get sun burned tomorrow, as I plan on driving past the northern target this go around.

The NAM is overdoing the dewpoints more than the GFS. Here you go:
http://weather.missouri.edu/People/limpert/18ZOBS_NAM.gif
http://weather.missouri.edu/People/limpert/18ZOBS_GFS.gif

Also, I've plotted 17Z buoy obs and PW derived from the GOES sounder. Here you go:
http://weather.missouri.edu/People/limpert/17ZOBS_PW.gif

The NAM is overdoing moisture return more than the GFS is, clearly. However, I still think it's being overdone by both the NAM and GFS. I'd agree that the good stuff is between 42002 and 42055, but at least at 17Z it looks like it's closer to 42055. I'd have plotted something more recent, but that's all I have available at the moment.

 

[Mike Hollingshead]

Just looking at these you'd think it'd all go fairly similarly in timing.

http://beta.wxcaster.com/models/eta/central/CENTRAL_ETA212_ATMOS_LSI_36HR.gif

http://www.wxcaster2.com/CENTRAL_ETA_700_GPHTMPWINDRH_36HR.gif

That looks pretty even over the whole dl from se NE to se KS.

http://www.wxcaster2.com/CENTRAL_ETA_500_GPHTMPWNDVORT_36HR.gif
Mid-level cooling looks similar over the whole dl too.

Toss in any slant tendancy from ssw to nne on the dl and I'd think it really evens out, at least into se KS.

Interesting the convective temp for Chanute and Coffeyville are both 77. Topeka at 81.