2014-06-03 FCST: NE/KS/CO/IA

[Skip Talbot]

Very volatile setup depicted on both the NAM and GFS. A deepening surface low is forecast over western/central KS, with a warm front draped across southern NE and a dryline down through central KS. A shallow trough, but with a strong impulse looks to bring 50-70 knots of 500 mb flow across the triple point located along the KS/NE border. There is also a very impressive southerly low level jet forecast over the warm sector with 40-50 knots at 850 mb.

Parameters are all there for huge supercells and significant severe weather: dewpoints in the mid to upper 60's, approaching 70 F to the east in se NE/ne KS bring forecast MLCAPE values to 3000 J/kg or more. Shear profiles are the most impressive, however: effective shear values just north of the warm front are an exceptional 90 knots. Effective storm relative helicity also exceptional with values well over 500 m2/s2 on and north of the warm front. Surface to 1km shear of 40+ knots, also extreme. Severe parameters are all extreme along the warm front where the hodographs are huge and curving.

Cap looks to be a significant player on this setup. 700 mb temps are a toasty 16-18 C in the Kansas warm sector. Significant CINH and LSI values are depicted in the warm sector, down the dryline in KS, and right on the surface low over central NE. Capping is less of an issue to the east along the MO river and extreme se NE/ne KS at the edge of the EML and where moisture is greater. Current lid strength values would suggest to me that the convective initiation will be suppressed down the dryline in Kansas or result in mainly elevated supercells.

The warm front looks like the serious player on this setup, perhaps in a similar fashion to May 11. I would expect storms to initiate near the warm front/dryline triple point by early to mid afternoon where low level lapse rates are steepest and with the enhanced lift along these boundaries. Like May 11, if storms go up right on the warm front, which they may be forced to do due to the strong warm sector capping, I would expect a quick transition to HP mode, due to the large amount of instability yet very low LCLs (600-1000 m immediately north of the warm front). Huge ground scraping, tornadic supercell. These storms are difficult to chase and very dangerous, so chasers should be on their guard, and constantly conscious of their escape routes and situational awareness.

Given the the hot temps and capping, I'd expect an initially high based storm to fire somewhere in extreme southern NE or northern KS off the nose of the low, and for it to track along the warm front in southeast NE. If the EML tapers off a bit more to the south, northeast KS may also be in play, but this target looks largely capped at the moment. Secondary targets might be southern IA, where the warm front is uncapped, and there is significant midlevel flow already in place by mid afternoon. This target may have issues with airmass recovery from earlier convection though. Another secondary target might be ne CO/sw NE where the moisture wraps around the low.

Primary concern with this setup is storm mode. We might have some training HPs supercells which are dangerous to chase due to concerns with visibility, flash flooding, and the large damaging circulations and RFD they produce. There might also be some issues with convection north of the warm front with the open cap and strong flow in place.

 

[Derek Weston]

Certainly a model monster at this point. Main concern is junk precip in vicinity of WF. If to the immediate south of WF can stay relatively precip free and reach instability potential, say, by, 21z, then watch out. NAM does depict narrow area where cap ought to be breakable. All that said, NAM fires off overnight precip that may throw wrench in things. Even with midday precip a few tubes may be realized. . .but mode/quality of tornado wouldn't be what it could. WF plays sure are fickle.

 

[Brandon Clement]

Excellent post Skip. Only thing I can add is that the Nam is showing quite a bit of convection moving over the warm sector on Monday with some more on Tuesday morning. Like May 11th this may leave an OFB in the warm sector south of the warm front that will allow for a couple isolated late afternoon cells going up in northern Kansas.

It sure would be nice to get a DL bulge south of the warm front with a fat OFB draped across the warm sector. It would allow for some options and may limit the chances of a chaser ball showing on radarscope.

 

[Stan Rose]

Ive only seen bigger STPs forecast on two other occasions...both times there were EF4+ tornadoes. That warm front looks downright scary...

 

[Jacob Ferden]

This is an interesting one. Thermodynamically it looks very impressive, to be sure. But I too am wondering what kind of storm mode we're looking at here. If you could get a supercell or two to fire on the dryline a ways south, but not too far from, the triple point, you might have a chance of photogenic tornadoes. But model guidance leaves me to believe the dryline likely stays capped, leaving the warm front. I think Skip's mention of the 11th is a good one, because there are strong similarities. In short, this to me looks like another deal that may be a prolific tornado producer if a supercell rides the front, but also another deal with extremely challenging chasing conditions. I also would say that there is a reasonable possiblity of rapid upscale growth into a large, possibly nasty, linear complex relatively early in the day's evolution. I've heard a couple people throw the D-word around on social media, and I think that is an entirely plausible scenario right now.

I expect I'll be chasing this one, but I also expect it won't be easy.

 

[Logan Karsten]

Skip, excellent post.

This could be one of those days to keep a distance from the mesocyclone as things could get very dangerous very quickly. With that said, there are several things I like about this setup. Skip made a parallel to May 11th, which is valid. However, I am hoping temperatures north of the warm front won't be as cold and clammy as that day. I hoping things can stay diffuse temperature wise to allow some storm structure. Ideally, I would like the shear to be more perpendicular to the WF as the forecasted shear could make things HP very quickly. The other problem is there will be a ton of chasers, so another thing EVERYONE needs to keep in mind on Tuesday. Given the shear, upper-level flow, meandering large tornadoes that don't follow typical motions are entirely possible.

Ideally, there could be a couple good tornadoes before things get crazy fast, but HP monsters are what I expect.

 

[Jeff Duda]

I think Skip, as usual, has covered most aspects of the setup adequately, so there's not much more to be said there. I've been looking at the CIPS analog guidance to see if this system is reminiscent of any big days in the past. One comes up - 29 May 2008. However, it seems that day had higher CAPE, less shear, and less capping, so I don't know how much it really means to have that day as an analog. I am worried about the 700 mb temps across KS - they're pretty high unless you get well east into the state, where I think lifting mechanisms for storms will be less prominent, although moisture is richer and CAPE is higher, and shear is still sufficient for a big-time event. I see a high chance that anything south of the warm front will remain stormless, though.

As far as chasing logistics goes, I hope for the sake of everyone who targets the warm front that multiple storms develop along it. Otherwise it's going to be a clusterf--k just like May 11th was. Seeing how bad it was on SN and on peoples' streams that day is probably enough to keep me from targeting that area (it's also farther out compared to secondary targets), so I will probably look to target E/NE KS instead of NE.

 

[JamesCaruso]

Skip - is there no chance that storm mode on the warm front might be other than a messy HP? In your 5/11/14 report you noted that if the storm that day had rooted right on the front or in the warm sector - as opposed to north of the front - then it might have been a more classic supercell. Can't we still luck out on Tuesday June 3?

Jim

 

[Brandon Lawson]

... As far as chasing logistics goes, I hope for the sake of everyone who targets the warm front that multiple storms develop along it. Otherwise it's going to be a clusterf--k just like May 11th was. Seeing how bad it was on SN and on peoples' streams that day is probably enough to keep me from targeting that area (it's also farther out compared to secondary targets), so I will probably look to target E/NE KS instead of NE.

I was out on May 11th. While the number of chasers on the roads was indeed excessive, i don't remember the traffic being a nightmare. That was probably more to do with a fairly nice grid of dirt roads and close proximity to I80. On the other hand, north-central and northwest Nebraska will offer no such conveniences. If storms are too far north and west, the eastward storm motions are going to be quite challenging to manage.

 

[Royce Sheibal]

I was out on the 11th and caught the storm about 5 minutes before the convoy arrived from Kansas. As a local Nebraska chaser who's familiar with the roads I really prefer to be the only guy out there. I'm hoping that the bullseye for isolated supercells alone the dryline keeps most of the chasers south on Tuesday so I can ride the warm front up here.

On a forecasting note, the models are showing some good PVA up along the warm front, but I've got a feeling that may be a result of Derecho formation... That being said, with such insane helicity values I'd expect a much different storm mode initially and then turning derecho after 9pmish?

The setup for today reminds me of another day infamous in Nebraska Chasing Lore.http://www.spc.noaa.gov/exper/archive/event.php?date=20040522 Big nasty HP supercells monsters. I don't know anyone that chased this storm but it didn't look fun.

 

[Skip Talbot]

Skip - is there no chance that storm mode on the warm front might be other than a messy HP? In your 5/11/14 report you noted that if the storm that day had rooted right on the front or in the warm sector - as opposed to north of the front - then it might have been a more classic supercell. Can't we still luck out on Tuesday June 3?

Jim

The surface pattern has changed quite a bit since I last posted. Instead of a sharper east/west warm front along 80, we have a more diffuse warm front/warm sector across much of central Nebraska where winds gradually back. Originally I was worried that stout capping would keep storms stuck on or north of the warm front, where LCLs are very, very low resulting in ground scraping HP storms. However, the more diffuse warm front now depicted may be beneficial for chasers, allowing a few storms to come off the triple point/dryline bulge, and each still being in very favorable parameters. LCLs aren't as ridiculously low toward 80, more along the lines of 1000-1400. The phenomenal shear values may help ventilate storms properly and keep our supercells in a classic state for longer.

The capping might throw a wrench in this setup. Cap opens at 18z and it looks to start closing after 21z thanks to that super warm EML that's pushing in from the southwest. Lid Strength Index values show stout capping on the surface low and dryline/triple point in Nebraska at 21z, where you'd expect a conventional initiation point and time. This is concerning, since to me that's kind of the bullseye target for storms and where all the parameters are maxed out. The LSIs suggest playing further east down the warm front, but that's always a gamble in terms of pinpointing initiation. We may see initiation super early, at noon (or even earlier), storms tracking east quite quickly toward Grand Island and Lincoln by early afternoon, and then gusting out and transitioning to HP by late afternoon, while the main dryline remains capped to the west. There could be a couple hours of tornado play in there, but this looks like it might be an early show that ends early. Initial target is from Kearney to north of Grand Island at 18z to 21z. I'll try to write a more detailed forecast with some plots later.

 

[John Wills]

Great forecast Skip! I have to agree with you on most everything about the setup tomorrow. Not sure if I'm totally buying the placement orientation of the wf tomorrow, but with the enviro, that is only a matter of where and when not if imo. The dry line play looks much too iffy to fool around with tomorrow. With temps forecast to be near 100, I see a cap in place that will be hard to break and if broken, the greatest threat will be high based supercells, something I don't think is worth while with the wf as juicy as it is. Currently targeting a triangle of arapahoe/Ansley/grand island, but may be shifting as situation becomes more clear tonight and into tomorrow. Will be leaving Chicago area tonight and be in place by late morning.

All that said, I also agree we're all going to have to be real careful tomorrow, with large hail and massive tornadoes possible, it will be important to keep a good distance with respect to cores/updrafts. I see storms quickly developing from initiation to tornado phase and therefore will need to be very cautious. Not a day for any new chasers to get in the way. Despite low LCLs, it will be important to remember that safety comes before anything even if it means missing a good line of sight to stay far enough away.

 

[JamesCaruso]

Skip, thanks for sharing your updated thinking. I am encouraged by the prospect of something other than ground scraping El Reno type HPs. It will still be a high-end day that will require great vigilance, escape routes, and the willingness to bail in the name of safety. I was not out here for El Reno or for May 11 this year, but even Memorial Day east of Garden City TX there was a time that we were bumper to bumper on the one eastbound road, meso behind us moving southeast, and no southern escape route... I do not intend to be in that position with a true beast tomorrow...

Anyway, as John and others have said, a dryline play does not look realistic tomorrow - not only because of the cap, but also because (at least on the 12Z NAM) there does not seem to be much convergence along it, with southerly winds in a broad portion of the warm sector, except maybe immediately south of the warm front which I guess pretty much still qualifies as the triple point play.

We are repositioning today from Hays KS to Kearney NE, will check the 00Z models tonight and then finalize a target in the morning. Sounds like an early day so glad we can be pretty close to where we need to be tonight.

Hopefully Tuesday will redeem this chase vacation, in which we have seen decent storms only two days since starting Saturday May 24!

Jim

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[JamesCaruso]

Forgot to add, the 12Z NAM shows precip all morning into the afternoon... Any thoughts on that? Hopefully it's not a mess of storm clusters that just intensify in the afternoon, as opposed to pristine initiation...

Jim


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[Andrew Stoller]

The 18z NAM is trending a tad more west with the dryline bulge/warm front dryline triple point area. Just east of North Platte would be an ideal target area to get on convective initiation early.