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

[Van DeWald]

The EMC 4km WRF option is looking awesome. Check out F23-F27 time frame, showing initiation near central Kansas on the 1km simulated reflectivity.

http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/

* Edit * Looks like Alex and I posted the link at the same time.

 

[Bill Hark]

After a quick glance at the 00Z outputs for the WRF and GFS, I am not as enthusiastic about Thursday. My main concern is veering of the 850 winds on both models except in northern Iowa. On the WRF, surface winds are backed through Iowa into NE KS and NW Mo. The GFS is similar for 850 winds and surface. Dew points will be marginal that far north with only a narrow area of predicted decent CAPE following the Missouri. I would position myself on the south side of South Sioux City near routes south and west. Unfortunately, there are not a lot of crossing points along the river

Bill Hark

 

[Mike Hollingshead]

Yeah Bill, that area is bugging me, for one it's closer and two it should go first most likely. I could really see a storm firing on the sort of little inverted trough nne of the sfc low. Nose of the mid-level jet slamming in there. The NMM WRF radar thing makes me fear it even more. On the Total column condensate (mm) loop you can see that dryslot slowing and curling west and that storm initiating there where that'd intersect the cold front/inverted trough. If that thing looked like it got better moisture feeding west to it I might be more inclined to go for it. As it stands, I think I'm heading to sc KS somewhere.

 

[Ilya Neyman]

Things are looking more initiation-friendly on latest models tonight.

Subtle-moderate vertical motion for ascent is hinted at by the NAM across W-NW-NCNTRL OK and S KS, with general favorable upper pattern on GFS. In addition, NAM shows a shortwave emanating from the closed low and moving across NW OK-SW KS with its leading edge of lift up to about I-35 at 00z near Enid-Ponca. GFS doesn't have this, but its grid resolution may be the reason. What the gfs does have is a hint at a convective attempt near 44 between OKC and Tulsa, and other one along the KS-OK border. This is important because it has been consistently showing this until this morning when it went dry, well now its back.

Very healthy dewpoints are infiltrating S. TX at this hour and expect those to continue. I think dews in the 65-66-67 range will be common in the moist sector of OK by late afternoon and would not rule out a 70 here or there.

In addition, the region right along the Red River needs to be watched carefully as well.

Still a question of initiation at this point, but the probabilities have just risen.

 

[David Wolfson]

As others have said, the picture has improved greatly in the 00Z runs. The 24hr RUC pulls 60+ dews north of Omaha, and the mid-level energy rotating through KS in the after 18Z looks to mix down as a (hopefully) raging dry punch. My bets are definitely on initiation off the dryline somewhere, although if I were already up around Lincoln/Omaha/KC a triple-point play looks pretty good, too, if there turns out to be a triple-point, which is up-in-the-air (as it were).

In line with the consensus this evening, starting from OKC, I'm looking to initially target El Dorado, KS, by early afternoon with the active possibility of having to adjust up or down rapidly as far as Omaha and Ardmore through the afternoon. Prepare to follow east options as mature storms move north of east at 30kts or so.

 

[afischer]

I think any tornado potential tomorrow is going to hinge on subtle mesoscale details over a relatively small corridor. Strong vertical motion with the upper feature is still forecast to overtake the cold front & triple point by around 00Z, and I'm assuming this will be the favored area for initiation. I'm not sure about discrete mode there given the shear vector orientation and intense forecast ascent, but I guess there is a bit of crossover nearer the triple point. If a discrete storm can move off the triple point it could certainly "spin" as it interacts with the accelerating LLJ nose over east central KS. If we can get initiation farther south on the dryline, naturally these would have the best shot at remaining discrete given relatively weaker large scale lift and the boundary orientation.

I'm concerned about how strongly surface-based storms will remain near & after dark (particularly since the vertical motion is generally lagging the warm sector), but this is mostly based on model guidance. The moist boundary layer that will shape up tomorrow in eastern KS is forecast to be disrupted with time by the accelerating LLJ in both NAM and GFS soundings (warming and drying spreading in aloft from the SSW). Accordingly, inhibition appears to become a problem pretty quickly by 03Z: http://beta.wxcaster.com/models/eta/central/CENTRAL_ETA212_ML_CINH_27HR.gif. The CRP and FWD RAOBs tonight look nice though with a 150-170mb deep moist layer, and if this depth of moist layer survives northward and remains backed up against the triple point/dryline then the tornado potential near/after dark would seem to be heightened given a discrete storm.

 

[Chris C Sanner]

I think the SPC sums it up best with the new Day 1 Otlk

GIVEN THE RETARDED MOISTURE RETURN...

Right now I'm iffy on if it is worth the drive for a possible cap bust. At this point I've had two already and gas is not cheap by any means. I hate to say it, but I'm almost thinking of sitting this one out because of the lack of funds in the coffers and the fact it's a marginal day...at least for right now. The shear, cape, etc. all look supportive, but the moisture, forcing and capping are all going to really throw a monkey wrench in plans. If I had to pick a target right now, it'd prolly be Stroud to Cushing as a happy medium between gas prices and reality.

If storms get going, it could be late and there may not be much daylight left. Then again, tomorrow is one of those days that if a few things are forecasted a bit off by the models, it could go either way. It's a waiting game but I am leaning on not going at this point, which will change several times over.

 

[mark plate]

Things are looking more initiation-friendly on latest models tonight.

Subtle-moderate vertical motion for ascent is hinted at by the NAM across W-NW-NCNTRL OK and S KS, with general favorable upper pattern on GFS. In addition, NAM shows a shortwave emanating from the closed low and moving across NW OK-SW KS with its leading edge of lift up to about I-35 at 00z near Enid-Ponca. GFS doesn't have this, but its grid resolution may be the reason. What the gfs does have is a hint at a convective attempt near 44 between OKC and Tulsa, and other one along the KS-OK border. This is important because it has been consistently showing this until this morning when it went dry, well now its back.

Very healthy dewpoints are infiltrating S. TX at this hour and expect those to continue. I think dews in the 65-66-67 range will be common in the moist sector of OK by late afternoon and would not rule out a 70 here or there.

In addition, the region right along the Red River needs to be watched carefully as well.

Still a question of initiation at this point, but the probabilities have just risen.

I will eat the keyboard of an AWIPS workstation at our office if a dewpoint hits 70 in Oklahoma tomorrow...and I'm talking a legit dewpoint...there's several sites that always report bogusly high dewpoints (Ardmore, Poteau, and others). Let's see if we can even get one mesonet site to hit 65 before 22-23Z...that will be an accomplishment. Any morning low clouds...and there may not be many in eastern Oklahoma...will mix out quickly due to the thin moisture that will not really deepen until nearer 00Z. Some of the drier air is bound to mix down and offset the advection of higher surface moisture from the south. This will likely keep the majority of afternoon dewpoints in the 60-63 range as others have recently mentioned.

 

[Jeff Snyder]

I'm increasingly optimistic about the chances in eastern KS and northeastern OK as well, as an impressive LLJ rapidly advects moisture back into the risk area. As Don G. and others have noted, area VWPs and profilers in OK and TX are showing 45-70kt flow right off the surface, and buoys just off the TX coast are now showing 68+F Tds. I'm actually a little surprised to see how well moisture return appears to be going, as even far southeastern TX (i.e. Houston area) is now seeing Tds ~65F. Normally I would laugh when thinking about chasing the next day when the juice is that far south in Texas, but we also don't normally see 40-70kt flow just off the deck all the way into the western Gulf of Mexico. 63-66F tds seems likely as far N as the OK/KS border, and it's possible such moisture will be able to make it farther north (we'll see how the moisture looks just above the sfc on the 12z soundings). And this coming from a guy who is usually very bearish when looking at forecast Tds in these "last-minute" moisture return scenarios...

In regards to moisture, I'll just say that I disagree rather significantly with the very conservative (IMO) SWODY1 that was just issued. I could see the argument for only high-based supercells if we were talking about 55-58F Tds, but certainly that SPC forecaster doesn't think Tds will be that low tomorrow...? Check out --> http://hoot.metr.ou.edu/surface/obs/spl for a loop of sfc obs w/ Td contour for the past 12 hours... And you know moisture is spreading northward faster just above the sfc. Regardless, I guess I'm just confused as to why the Day 1 is so pessimistic when it comes to the tornadic supercell threat tomorrow.

My concern w/ a cap bust in OK/KS remains, but I think it could be alleviated if the 850mb winds can avoid veering so much during the morning through early afternoon (scouring 850mb moisture well to the east of the sfc dryline).
NAM forecast from this evening shows minor 850mb Qvector convergence over much of OK and southeastern KS, which is certainly a good sign. I'm not sure what to make of the persistent signal for 700mb subsidence along the dryline on the NAM, though.

Overall, I'm liking the area near Bartlesville and northward a bit. We'll have 2 mobile radars out tomorrow (W-band and X-band phased array), so it'd be awfully nice if Ma Nature would throw us a bone and let us collect good data!

 

[mark plate]

I think the SPC sums it up best with the new Day 1 Otlk

The new SPC day 1 I feel is dead-on...it agrees with what me and other forecasters in our office were thinking all evening. We were afraid they might go moderate, but we all felt slight remains most appropriate for now. Their discussion is pretty much dead-on too with what I would have written...they say high-based supercells...I said LPish...different ways of saying the same thing.

 

[Alex Lamers]

Well the NCEP 4km WRF NMM has just come out (00z Run). Looks very similar to the 4km SPC run! If these verify, the risk area may shift a bit further west. Still looks like supercells developing in KS 21-00z. Then those go multicell afterwards and more isolated development in NC OK or SC KS 00-03z.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/hiresw/00/model_l.shtml

I gotta say...you get north of a Pratt to Emporia line, and the SRH really drops off and hodographs become nearly linear. While early development may occur earliest further north into NC/C KS...I wouldn't chase that stuff, and hold off for what may develop later in better moisture closer to the OK border.

Still iffy on whether or not the cap will break. Anything from Guthrie up through Wichita and points 50-100 miles east has a chance to be a significant supercell though. Worth a shot I suppose. I won't be heading out.

AJL

 

[Gabe Garfield]

The new SPC day 1 I feel is dead-on...it agrees with what me and other forecasters in our office were thinking all evening. We were afraid they might go moderate, but we all felt slight remains most appropriate for now. Their discussion is pretty much dead-on too with what I would have written...they say high-based supercells...I said LPish...different ways of saying the same thing.

I have to respectfully disagree. In my opinion, this setup is only a couple of unchecked boxes short of a synoptically evident tornado outbreak. I think that at least a mention of isolated tornadoes would have been appropriate, given the fact that we already have well-mixed 60 F Tds in Oklahoma now (per the Mesonet). (And yes, the B-L is well-mixed; the wind is absolutely howling due to intense mechanical mixing. So, what you see now is at least what you'll get tomorrow.)

Personally, I think that Ilya Neyman's forecast is not too far off. EDIT: I suppose the crux of the matter is whether or not the winds just off the deck can back before substantial mixing occurs. If they can't, I am a bit concerned that the moisture will be scoured above the surface along the dryline. We shall see...

P.S. By the way, the moisture is not shallow; check out this evening's observations.

 

[afischer]

Based on past experiences I'm not really a fan of intermediate NAM-WRF runs, but it's intriguing that the 06Z run is showing decidedly more backed 0-2km agl flow by 00Z this evening and onward ahead of the dryline than the previous run did... and accordingly retains a deeper moist layer and far less hallacious 85-7H cap. FWIW, it's also wanting to trigger convection in central/eastern OK, assumedly off the retreating dryline.

 

[Brandon Lawson]

I was just looking at the 06z NAM run myself and it sets up incredible conditions by 03z right on top of the KICT area. Everything looks impressive with the exception that it still is not breaking out much in the way of precip. I hate to get my hopes up since the NAM is usually a let-down, but it looks really impressive at the moment. If this is sign of a trend in the models, could be an interesting day. Also, the mesonet is currently showing widespread 60 dewpoints over west central Oklahoma. Man oh man!

 

[Darrin Rasberry]

Darrow's forecast is kinda letting off the hail potential way too much. I don't particularly like the way he puts things ("retarded moisture returns"?) but his synopsis for SW IA is dead-on, as well as his extension of the risk north along the warm front, as was discussed by myself and a few others at length here.

Speaking with my chase partner last night I mentioned I'd put 5% tornado risk over SW Iowa, as was done, but I think that the risk should be upped to perhaps 10% over NE Kansas/NW Missouri/far SE Nebraska with an upgrade of the area to MDT. Although the MDT area I'd outlined probably is too small for SPC standards, I still see a chance for a localized tornado or three in that area if something can push that cap.

Nonetheless I woke up today with a migraine after securing a day off yesterday (of course), so my chase target will remain 50-100 miles west of my home in Ames, probably around Jefferson, Iowa, to play the warm front if I don't get sicker.