2014-04-26 FCST: KS OK TX

[Matt Hunt]

Indeed it looks like the same issues as yesterday. Those LCLs are just way too high for a decent tornado threat. It's getting too hot along the dryline for 60s dews to be sufficient. I've been looking more and more toward the northern target along the NE/IA/MO/KS borders. There's somewhat of a triple point just to the west, which should allow for a little greater forcing. Moisture could be an issue in this area, and may be a case of just in time moisture, but I'm questioning if 60s dews can make it up that far north. The plus is that the air temp will not be as high, with low 80s, and cooling at dusk into a much more manageable TDD. Shear is a bit weak as well, as only 40 kts at 500mb will make it up there. Still, this seems like the area with the best shot at a tornado if a storm can root itself in the warm front and get enhanced helicity. It's a much shorter drive for me as well, so I may be willing to take the risk of a bust.

 

[Chris Wilburn]

I am very unimpressed as well for the same reasons you all mentioned above. There may be a very narrow window for tornado potential if storms can move into the higher dews east of the dryline late in the evening. CAP looks like it could be an issue as well, and even if we do get storms late in the evening, the CAP will begin to quickly fill in at dark. I haven't looked much at the northern traget Matt, but going to give it a look over. Moisture might be able to pool along the wf and create lower LCL's. However, it's even further away from the upper level support. No way to win on this one. Too bad we can't combine the best of both ingridients from the two areas. Talk about a disappointment, this day about 48 hours ago looked amazing. I know it was even too early then, but definitely disappointing. I will probably chase anyway, more than likely along the dryline. Here is to hoping dews are about 5-8 degrees warmer than what they are currently forecasted by the NAM.

 

[Taylor Wright]

I think we all had a hunch this one was too good to be true from the beginning with how quiet this year has been. We all but asked for the NAM to tone this down. I was hoping I could catch my first decent tornado since 2012, given that 2013 was a tumultuous, bust-filled year. Regardless, I've now been keeping my eye on the northern target as SE Nebraska looks to have the better rotation. A corridor of weak cap from central Kansas to Nebraska on the dryline should allow for storm development, but it might be before any of the upper level support gets there. It also looks like the mid-level streak won't reach the dryline until well after dark. However, 40-50kts of 500mb might be sufficient for a couple isolated slow moving supercells just before dark. This is reminding me a lot of some of the April setups last year. That is, weak flow with good thermodynamics spins up one or two supercells that drop a tornado before dark. Only thing is NAM is very stingy with low level helicity. Looks like a 10% hatched area along the dryline if we're lucky with a potential for a cap bust. Unless the NAM starts trending towards the GFS and ECMWF (which it hasn't so far), my first chase might not be until May, if there ever is a decent setup.

 

[James Gustina]

Looking like very weak height-falls and crap for sfc convergence along the dryline may doom this one further south, and that's not even including the questionable quality of moisture. The NAM also appears to have stupidly warm H7 temps along the dryline between 10-12C. As others have mentioned, the T/Td spreads for this one look iffy considering it might be 90/60 with already poorly distributed BL moisture. The wind profile still looks decent throughout the warm sector along with MLCAPE cracking 2500 j/kg throughout the entire warm sector, but it all comes back to whether or not the storms that may go up on the dryline will be anything more than high-based garbage given the moisture depth/quality. Might end up being another case where a really good mesoanalysis the night before/morning of will be the deciding factor on picking a target, because right now I'm not sure where I'd really go.

 

[Skip Talbot]

I agree with the less than optimistic sentiments here. I don't really see much of a tornado play at all on Saturday. I've found Earl's plots of the lid strength index and 3km cape to be great filters for weeding out tornado potential in setups. Based off those two, the only places with a marginally open hole in the cap and some low level instability to work with would be near Nebraska City on the warm front and then down on the Red River into north TX. The dryline looks dead otherwise for tornadoes. Elevated supercells? Sure.

I'm really torn between these two ends of the warm sector. That northern end up by the warm front looks like it's "just in time" moisture as you guys have said. 45 Td's the morning of and that's supposed to jump up 20 degrees by late afternoon. And where's the lift? If there cap were wide open, or there were boundaries criss crossing the warm sector, I'd say sure, something could pop by the warm front. That trough lags way to the southwest though and you've just got some light southwesterlies aloft. Capping is stout too. You really need some strong forcing to get stuff to pop up there. On the other hand, there's a thermal axis forecast across northern KS into southern NE with temps approaching or exceeding 90. I could see some updrafts coming up on that axis where the low level lapse rates are super steep, the convective temperature is reached, and perhaps if there is a subtle impulse coming up from the southwest. A super super high based cell, due to the 40's dews that far west, would then take its sweet time tracking northeast into the warm sector, finally lowering as it hits the moisture rich warm sector on the MO river, and then maybe producing as it approaches the warm front. CIPS analog was saying a 3/22/11 Creston, IA type analog, which basically did the exact same thing.

The other play would be way down on the Red River, where you're getting better upper level support is that trough noses in. Moisture may be better established down there, but the 700 mb temps are toasty. Still there's a crack in lid strength index that might allow for some surface based storms, but it's really really skinny, perhaps too skinny, and those cell will just overrun it quickly if they go up. Maybe a window for a tornado or two at dusk when the boundary layer starts to cool and that low level jet ramps up. Otherwise I'd expect updrafts to struggle against the warm temps aloft and lack of forcing.

 

[Zack Hargrove]

I have a hard time basing my forecast off the NAM. The 700mb temps are much higher on the NAM than the other models. On top of that, outside of 48 hours the NAM is pretty terrible and it is a clear outlier for this system. The GFS and Euro paint a more attractive picture for Saturday. It will still take boundary layer cooling to lower bases, but there have been enough setups where that's happened in the past for some optimism.

 

[James Gustina]

The Euro does paint a very nice looking scenario for both Saturday and Sunday. I'm still leaning towards pessimism just considering what the season has done so far (not the best thing to base an opinion off of I know). I'm guessing the actual setup will be somewhere between the GFS' more moderate solutions with a few decent supercells somewhere on the dryline. If LCLs get under 1500 m then I'd be more than willing to bet on some nice tubes.

 

[Derek Weston]

The Euro does paint a very nice looking scenario for both Saturday and Sunday. I'm still leaning towards pessimism just considering what the season has done so far (not the best thing to base an opinion off of I know). I'm guessing the actual setup will be somewhere between the GFS' more moderate solutions with a few decent supercells somewhere on the dryline. If LCLs get under 1500 m then I'd be more than willing to bet on some nice tubes.

To me they all look pretty similar as of 12z for this Saturday. Not much differences in advancement of the trough or warm sector. To me it looks like we'll probably have relatively sparse coverage along the DL, some nice supercells, and possibly a few tornadoes in the 7-9pm timeframe.

 

[Logan Karsten]

As others have stated, I too are having serious reservations about this setup. The models continue to struggle in bringing in deep layer moisture, and combined with high surface temperatures near the DL, high LCLs will be a problem. In addition, the forcing is now too slow and won't arrive until after dark.The possibility is there for a supercell or two to form along the dryline in Texas where somewhat deeper moisture will be present. However, this setup has gone to a very conditional slight risk. Skip caught it pretty well early on a few days ago before the models went to crap. I held out hope that yesterday's system wouldn't push the CF as far south as it did. Alas, welcome to 2014, where your hopes and dreams are crushed.

 

[Jeff Snyder]

It's been a roller-coaster of chaser-related emotions that past few days as we've watched this potential event get closer and closer. I never really pay particularly attention to 5+ day forecasts, so I didn't get caught in the hype that some seemingly got swept up in based upon 180 hour model forecasts that showed a synoptically-evident tornado outbreak. Since I really started paying attention to the model forecasts Wednesday evening, I haven't been particularly impressed with the setup. The overall synoptic environment looks generally favorable based upon pattern recognition, but the timing appears to be ~12 hours off for a chaser-friendly event in decent terrain (at least south of the KS/NE border -- I haven't paid too much attention to the northern areas since I'm not likely to chase up there). If the trough speeds up (e.g., delays cutting off) 9-12 hours, Saturday would be pretty impressive (moisture concerns aside); if the trough were to slow down 9-12 hours, Sunday would be mighty impressive. That said, the current sounding observations and latest 12z model solutions rolling in now have caused me to sit up a bit straighter and pay a bit more attention to both days. As noted, I'm looking particularly at the western N TX through southern KS environment, so lack of more detailed discussion of the NE potential shouldn't be attributed to my lack of confidence in that area producing.

I'm still not sure what to think about this weekend in terms of chaser-friendly (e.g., decent terrain/territory and daylight-hour convection). Morning soundings from BRO, CRP, and DRT show very decent moisture profiles, with mean mixing ratios of 16.0, 14.1, and 13.2 g/kg, respectively, and a ~150 mb deep layer of seasonably-high moisture. Perhaps the GFS and NAM are catching up with this, since the trend of reducing Tds for Saturday afternoon appears to be reversing (note >1.4" PW up to I40 on the GFS by early evening Saturday). For Saturday... The 12z NAM still has the leading edge of the 500mb vort max way out in western NM by early Saturday evening, so there's little forcing for ascent aloft until early Sunday morning. That said, if moisture return is robust enough after 00z, there could be a whopper or two off the dryline near sunset. See, for example, this sounding valid just W of LAW at 3z and note that surface-based convection would be a fair bet (though the high RH and poor lapse rates aloft suggest the model is modifying the sounding for convection) --http://tinyurl.com/l347o7w . The GFS forecast soundings (for whatever trust we can place in them, which should be limited) are showing the favorable sickle-shaped hodographs by 00z, a general shape that has been noted to characterize environments that support significant tornadoes. The KS/NE border area is still open as well -- http://tinyurl.com/ku65fmx . *Update: the 12z GFS is coming in with higher PW and lower tropospheric moisture compared to the past 3 runs, at least through the currently-available time of 15 z Saturday.

Edit: For those who want to track moisture recovery without having to deal with issues about low moisture depth (e.g., 2 m surface observations sometimes aren't representative of the lowest 75-100 mb of the troposphere), you can look at GOES-derived precipitable water at https://cimss.ssec.wisc.edu/goes/rt/viewdata.php?product=pwa_us&time=latest&imageType=image . Since PW isn't retrievable from satellite where there are clouds, it may only be useful at times (such as right now) and in certain areas (such as in Texas and Oklahoma) depending upon cloud cover. Again, though, since TX is relatively cloud-free at the moment, it's another tool to have.

 

[Skip Talbot]

Skip, thanks for your analysis. Would you mind sharing a link for the lid strength index you use? And could you explain how it is different from, and advantageous to, simply looking at 700mb temps?

Thanks!


Sent from my iPad using Tapatalk HD

Moved this discussion to:
http://www.stormtrack.org/forum/showthread.php?30439-Lid-Strength-Index

If the 12z NAM is accurate, the LSIs and 3km CAPE plots are both pointing at the southern end of this setup. Particular these two plots:

You need decent low level instability and a nice hole in the cap to get a surface based supercell and tornado. What I see here is a trend toward both of these things in sw OK between 0z and 3z. You've got a shot at a sunset/dusk tornado down there. The warm front in NE does not look as favorable. There's some what of a hole up there, but there's meager low level instability. Kansas is dead to me. I'd be super surprised if anything more than a spout or spinup comes out of there.

More than any other plots, these two plots persuade me to make the long haul down to s OK from IL instead of playing the closer to home warm front.

 

[Andrew Stoller]

The backup RUC is still operational and goes out 24 hours; the current 17z shows the dryline much further west tomorrow at 17z than the NAM or GFS. This seems encouraging. I'll be watching that like a hawk tonight to see of the GFS and NAM verify; the GFS has been trending that way. That would probably mean less deep moisture along the dryline but possibly better cooling/flow aloft as what moisture is availble will be closer to the upper trough.

 

[Brett Roberts]

The 12z ECMWF remains consistent in depicting far worse moisture quality tomorrow afternoon than the GFS/NAM. Given what we just saw unfold over the same region on Wednesday, among many reasons, I'm inclined to believe it. In all likelihood, we will see moisture mix out with surface dew points of 56-60 F throughout W OK and NW TX during the daylight hours. With temperatures warming well into the 80s, T-Td spreads will once again struggle to stay below 25-30 F. Thus, even if storms develop well before sunset, I'm not sure they'll be a lot more impressive than the utter garbage we saw Wednesday. There is potentially a narrow window right around sunset for everything to come together somewhere in W OK or NW TX, but it doesn't seem all that probable.

The after-dark scenario is an interesting one. All models agree that significantly better moisture will surge into S OK and NW TX between 00z-06z. At the same time, the upper jet noses in on the downstream side of this negatively-tilted trough. Nocturnal tornado events are fairly rare in the Plains, and I'm still doubtful that we'll have true surface-based storms ongoing at 03z-06z. It's a possibility that can't be discounted, though.

All in all, the story of 2014 continues: a 6-12 hour timing change on either side with this system could have made a world of difference for Plains chasers, much like 4/2-3 and 4/12-13.

 

[Dan Robinson]

My last-resort option for Saturday was central/western Nebraska. There is less instability, but the wind fields are beautiful up there closer to the low - and there was some hope that the moist axis would barely reach northwest enough for the boost from upslope to hopefully make something fire. Even that looks like a pipe dream now, with the upper support arriving too late and the cap no better than down south. At this point, I'm electing to not chase Saturday. I am, however, setting my alarm for 4AM to check surface obs. If I see that the moisture is surging north faster than progged, I'll make a last-minute dash out the door. But I think it's far more likely that I'll be going back to bed.

 

[Mike Smith]

Let me chime in after looking at the 18Z models. I am very concerned about tornadoes after dark in the NW half of Oklahoma (i.e., northwest of an LTS-Miami line) and south central Kansas. The 03Z sounding for Kingman, Kansas (from the 18Z 13km NAM) is still favorable for surface-based convection. The same is true at Vici, OK. In Kansas, the 0-1km helicity is above 150 at 03Z and the EHI's area adequate. Heights fall like crazy after 00Z.

So, I don't often get concerned about nighttime tornadoes in Kansas and Oklahoma but this may be a dangerous situation in that regard with the threat continuing all night because of the strong dynamics.