2015-04-24 EVENT: TX/OK/KS/AR/MO

[James Hammett]

Northern targets get nailed from both sides...ongoing convection south blocking flow and ongoing convection north with its cloud cover and cold pools killing the juice near the front.

Looks like another setup plagued with problems to me. The supersonic 300mb jet max may lead to issues with storm mode, storm motion may be uncomfortably fast, and the instability axis is weak and narrow thanks to progged clearing issues/ongoing convection south in the warm sector that Jeff and others have mentioned.

On the other hand 12Z WRF shows a pretty good axis of 0-3km MLCAPE on the nose of steep low level lapse rates in the SE quadrant of Kansas which may help make up for the poor deep layer CAPE. Still not enough for me to pull the trigger.

 

[Jared Farrer]

Northern targets get nailed from both sides...ongoing convection south blocking flow and ongoing convection north with its cloud cover and cold pools killing the juice near the front.

Looks like another setup plagued with problems to me. The supersonic 300mb jet max may lead to issues with storm mode, storm motion may be uncomfortably fast, and the instability axis is weak and narrow thanks to progged clearing issues/ongoing convection south in the warm sector that Jeff and others have mentioned.

On the other hand 12Z WRF shows a pretty good axis of 0-3km MLCAPE on the nose of steep low level lapse rates in the SE quadrant of Kansas which may help make up for the poor deep layer CAPE. Still not enough for me to pull the trigger.

I agree with James, NAM/GFS with the progged 500/300mb wind speeds with lacking temps/dews spells out potentially messy setup as far as chasing is concerned! Cloud cover and convection will definitly limit destabilization in a very narrow warm sector closer to the low. Forecast storm motions are unpleasant but it may not be quite that bad in reality come tomorrow? Pretty tough forecast really. Just have to wait and see.

 

[Brian McKibben]

Well, 00z NAM puts the DL much further west than previous runs. Now it is around Altus to Woodward around 21z (maybe just a little east). That is significantly further west. This puts OKC metro in play. 12z 4km WRF show cells that far west and i simply discarded that this morning. Then 18z NAM shows storm near I35. Now 00z NAM and 00z 4km NAM show storms west of I35 before 00z Sat.

This could be a game changer if the trend continues.

 

[Jeff Snyder]

Excellent summary as usual, @Jeff Duda !

00z soundings from LCH, CRP, BRO, etc., show very good moisture magnitude and depth (e.g., mean mixing ratios of 15.4 g/kg and 17.8 g/kg at LCH and CRP, respectively). DFW had 13.3 g/kg, though with an obviously bad surface Td ob. Some of this seasonably high moisture isn't going to make it to OK/KS owing to some veering of the flow below 850 mb, though.

The 00z NAM, as @Brian McKibben noted, is considerably farther west with the dryline. In addition, although it has a convective complex moving near the Red River mid day, it now initiates scattered convection along nearly the entire length of the dryline. CAPE is still not particularly impressive, but with less widespread QPF, the instability corridor does look larger than previous forecasts largely had shown. This puts the I35 corridor in the threat area. The 4 km NAM produces considerably more cold outflow from the N TX / S OK mid-day convection, which advects northward and kills storms that develop near the dryline. That said, the theme remains that KS looks to have the best chance for a long-lived tornado threat since it's less likely it'll be affected heavily by outflow from storms to the south. The 850 mb flow is less veered in KS, which is also a plus.

I'm not particularly interested in chasing in TX tomorrow, so my eyes will probably be in northwestern OK northward to the warm front, wherever that sets up. The most obvious play seems to be that front, but anywhere in KS looks fine to me. If the mid-day QPF bomb near the Red River doesn't materialize (it originates in west-central Texas tomorrow morning), destabilization across OK and TX likely would be more robust. I'm pulling up a lot of forecast soundings from the 0z NAM that support a chance for significant supercells ahead of the dryline and behind the early/mid-day convection.

 

[Chip Redmond]

Biggest things that stick out for me tomorrow: trend towards slower storm motions, better backing at the surface, and less worked over air. All continue to point to my target (and shift west/southwest as anticipated) mentioned earlier. Starting to get confident!

Chip

 

[Drew Terril]

I was originally targeting Coffeyville/Caney/Independence due to anticipated storm motions. I didn't want to be right at the initiation point and not be able to keep up, especially in the Flint Hills. I'm thinking Alva, no further east than Enid. Definitely a big change in plans on my part.

 

[Rodney Nonamaker]

I, as well am curious to see what takes place along the I-70 corridor. A little biased living in Topeka, but all the same. I won't be off work till 8, so no chasing for me. If so, as it looks from the 00z Nam 4k, I'd be positioning myself just west of Salina.

 

[JamesCaruso]

I won't be chasing as I am in the Philadelphia area still three weeks and two days (but who's counting?) away from my chase vacation. So just took a quick look at things just now and if I were out there I, like Rodney, would target along I-70 west of Salina, roughly the latitude of Ellsworth. Moisture and instability looks to pool along the warm front as it wraps toward the triple point, although there does not seem to be a truly well-defined triple point due to a more diffuse dryline with some veering winds / mixing in the warm sector. You need to be a little further east along the front to find backed winds, and they are not particularly strong. The strongest mid/upper flow is south of this region, but there is still ample shear along I-70 and as others have noted this might actually help if storm motion is not quite as fast as further south. Another concern is the relatively weak cap and the prospect of early showers/storms. At least there isn't all that much morning convection at the moment. There are still a good few hours to refine the forecast but unfortunately I won't have time to watch the situation evolve, facing a jam-packed day at work today Good luck to all who venture out!


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[Andy Wade]

Ouch. KFWS...water, water everywhere. With ongoing healthy shields of precipitation both along the Red River Valley and farther south, and some new convective development from DFW southwest right now, the Texas risk area is on the brink of a washout. I don't know how that big hatched tornado area is supposed to recover lapse rates with the best DCVA sitting well to the north and barely 7 K/km being advected in. Most of Oklahoma is probably hosed now. 4km NAM is out to lunch because it has no handle on the large areas of rain to the south. Moisture return into Kansas is there, but somewhat narrow and anemic thanks in part to the Red River activity.

The triple point shifting far westward into Kansas is also problematic, because the 850 jet core that had us all drooling over hodographs--let's be honest, the hodographs were the only thing to like about this event--will run through northern Oklahoma into the eastern half of Kansas. A storm coming into Salina at 00z may be an easy chase target, but it may not be a tornado machine either.

I want to go out but I can't find a target worth the drive right now.

 

[Dan Robinson]

This event has been a rather spectacular model failure on many levels. The moisture problems at the Kansas WF/TP target were evident early this morning, and was enough to get me to call off the chase at my last-minute decision time. I'm not a fan of setups where the ambient warm sector is so anemic that you have to rely on pooling along the boundaries to even have half of a chance. As others have noted, the upper support was already poised to barely graze the central KS target, and with the dryline now farther west, it seems that the jet might as well be down along the Gulf coast at this point for all the good it will do us. I was itching to chase *somewhere* today, at one point considering central Arkansas for a shot at a leading pre-MCS supercell, but the moisture/CAPE situation there looks just as dire with ongoing convection already threatening to ruin all hope. I'll be staying home today.

 

[Jeff Snyder]

00z model runs giveth. The 6z and 12z runs taketh away. The ongoing convection in TX has been more widespread than the 00z NAM/4km NAM had forecast, and this has put a major hurt on moisture advection in OK and KS. Heck, convective coverage is actually expanding right now near the I20 corridor near and W of DFW. Current vis sat indicates a lot of convective debris in TX and OK, but that shouldn't affect areas ahead of the dryline N of I40 too much. What will affect those areas, though, is a band of cirrus. Soundings at LMN and OUN aren't too shabby, with a convective temp of ~84 F at LMN and lower at OUN. Sfc obs show the best moisture (>= 68 F Tds) blocked up near the DFW area. OK Mesonet obs seem to indicate better moisture than the 12z NAM is forecasting at this time (~15z) with a decent corridor of 63-66 F Tds across central and western OK. That stream of 63-65 F Tds is pretty narrow by the time we get to the OK/KS border, though, where its being pinched by 60-61 F tds on southeasterly winds in eastern OK and veered sfc winds with tds in the 56-59 F range in far western OK.

The recent HRRR runs support the last couple of NAM runs in forecasting insufficient destabilization today in most of the previous risk area north of the Red River owing to cool low-level temps and marginal moisture. However, the HRRR and NAM aren't seeing the low-mid 60 Tds in OK (at least not the correct extent of them), so there is the chance that CAPE is being underforecast. Regardless, the main models agree with the SPC in showing a bimodal distribution of best severe chances today with a relative minimum in risk in OK. Mid-level warming on the warm/equatorward side of the mid and upper level jet does a number on lapse rates in TX.

I'm far less optimist than I was 12 hours ago when perusing the 0z models. I'm still modestly intrigued by the KS setup today since it looks like that the morning model runs may be underforecasting moisture return northward when comparing the 15z obs with the forecasts valid at 15z. I've all but given up on OK at this time, though I'll keep an eye on vis sat and sfc obs through the day.

 

[Kevin Rimcoski]

I hate being hours behind everyone. I just woke up and first thing I checked was radar and saw a lot of rain in southern OK and northern TX and cried a little inside

 

[Randy Jennings]

I was about to give up on today with all the morning rain over TX and the unimpressive lapse rates, but there is a sliver of hope still. Satellite is showing a clearing in central TX moving to the northeast, so maybe there is a slight hope. It would be ashamed to waste the good moisture, shear, and forcing. I'm not going to hold my breath. Like Ben said yesterday, a watch will likely get me out (likely to the south of the metroplex), but I likely will be disappointed.

 

[Brian McKibben]

00z model runs giveth. The 6z and 12z runs taketh away.

So true. I don't know what to believe anymore. I think I will throw the models out the door and watch Vis and Radar. I am interested to see what happens with the storms forming SW of Childress.

 

[Tom Dulong]

I would not give up on supercell/tornado potential for north-central TX this afternoon. Morning Area Forecast Discussion out of NWS FTW lays out the challenges of this complex situation quite well. Tail end of elevated convection moving through Dallas at current time. Surface boundary runs in e-w fashion along I-20 into low pressure center in Palo Pinto county.

I would not trust 12Z raob sounding for FTW...as the balloon was launched through ongoing showers/thunderstorms. Higher theta-e air is poised to move into the DFW metroplex, if the boundary can move northward. Recent surface pressure falls suggests this scenario. The SPC recently issued an MD for likelihood of Tornado Watch issuance for a good portion of north central TX in the next couple of hours.