May 15th - 20th Plains Storm/Severe disco

[Disc]

Impressive.

 

Pratt, KS

 

 

Great Bend, KS

[andyhb]

Pretty nuclear strength caps in those soundings, though.

[ZackH]

That's some crazy CINH, though...

[Disc]

Pretty nuclear strength caps in those soundings, though. 

 

For sure. Even with the cap those soundings are pretty impressive parameter-wise/hodos etc.

[baroclinic_instability]

Impressive.

 

Pratt, KS

 

 

Great Bend, KS

They are impressive from a kinematic standpoint, but one of the reasons the wind fields are so impressive is due to the inversion/cap itself.You will see soundings like that almost daily in midsummer across the plains (maybe not to that magnitude, but you get the idea) during the overnight as the nocturnal LLJ develops.

[jojo762]

Pretty nuclear strength caps in those soundings, though.

With CINH that high, Wouldn't that mean that any storms that do develop, if any do, that the mesocyclone would have quite the hard time drilling past the cap? Even though there is still high cape, and high shear?

[thewxmann]

Those soundings tell me that storms will be either dead or elevated by 06Z, and all tornado threat should be mostly done by then.

 

Nice EML though.

[brettjrob]

Hopefully everyone talking about a "thermonuclear cap" in those images realizes they're valid at 06z. It's quite common in late season High Plains setups for the model hodos at 00z to look somewhat lackluster, then become amazing at 03z when CINH has increased markedly. What you don't see is the in-between period, when the LLJ ramps up rapidly and existing supercells have a window to persist owing to VPPGF during that 01z-02z period.

[Indystorm]

Dense fog advisory issued for much of sw Kansas as moisture streams northward to prime the pump with 70 dews over much of OK as indicated in the SPC graphic posted by Smoke Eater above.

[andyhb]

Hopefully everyone talking about a "thermonuclear cap" in those images realizes they're valid at 06z. It's quite common in late season High Plains setups for the model hodos at 00z to look somewhat lackluster, then become amazing at 03z when CINH has increased markedly. What you don't see is the in-between period, when the LLJ ramps up rapidly and existing supercells have a window to persist owing to VPPGF during that 01z-02z period.

 

I was about to post this about the soundings being valid at 6z but I'm glad you handled it, this is what you can see with these more potent nocturnal Plains events, you have a window there where shear parameters skyrocket and CINH is manageable, and like you said, any supercells out there/developing could rapidly become tornadic.

Also, for Indystorm's point, yeah I have a 72 degree dewpoint at Alva per latest observations from the mesoanalysis page.

[Superstorm93]

KSNL is up to 77...

 

Gulf moisture is just surging on in

 

 

Trough looks decent

 

[Disc]

Hopefully everyone talking about a "thermonuclear cap" in those images realizes they're valid at 06z. It's quite common in late season High Plains setups for the model hodos at 00z to look somewhat lackluster, then become amazing at 03z when CINH has increased markedly. What you don't see is the in-between period, when the LLJ ramps up rapidly and existing supercells have a window to persist owing to VPPGF during that 01z-02z period.

 

I didn't even notice that they were valid at 06z. (It's been a long week with long hours at work) As you mentioned though, from 00z to 03z the hodos look markedly better on the 0z NAM.

[LocoAko]

KSNL is definitely faulty, looking at the mesonet observations. Still, it is awfully humid out there....

[andyhb]

KSNL is definitely faulty, looking at the mesonet observations. Still, it is awfully humid out there....

 

Yeah I was kind of figuring this given that the surrounding obs all day have been at least 4 degrees lower. Regardless, the Gulf is basically flowing into the Plains right now.

 

Also, the 00z GFS continues to look nasty on Sunday, the entire cap along the dryline in KS and OK is gone at 21z. I continue to notice a stronger sfc wind response on the GFS compared to the NAM.

 

As is the cap on Monday in OK (very weak to gone).

[jojo762]

KSNL is up to 77...

Gulf moisture is just surging on in

ScreenHunter_21 May. 17 23.36.png

Trough looks decent

ScreenHunter_21 May. 17 23.38.png

Look at that sharp dryline, you go from mid to low 60's DP's in SW Kansas to teens and even single digit dewpoints in SE Colorado...

[thewxmann]

Yeah I was kind of figuring this given that the surrounding obs all day have been at least 4 degrees lower. Regardless, the Gulf is basically flowing into the Plains right now.

 

Also, the 00z GFS continues to look nasty on Sunday, the entire cap along the dryline in KS and OK is gone at 21z. I continue to notice a stronger sfc wind response on the GFS compared to the NAM.

 

As is the cap on Monday in OK (very weak to gone).

 

The 12Z ECMWF also sides with the GFS, so that's good news for chasers. That said, the NAM tends to do very well (and outperforms the GFS) inside 48 h. The next few model runs will be important WRT Sunday.

 

The cap shouldn't be that much of an issue Sunday seeing that the broad base of the trough implies that the H7 flow advects an EML from NM, as opposed to something thermonuclear from Mexico.

[CUmet]

The GFS has definitely shown a secondary low of sorts further south towards NW OK that really backs the near-surface wind field across much of OK on Sunday.  This results in a rather potent juxtaposition of very unstable CAPE and very high helicity there.  The GFS has also increased the mid-upper level wind fields across OK as well over the past few runs, reflective of its trend towards a deeper trough, and this deeper trough also enhances the synoptic forcing for vertical motion further south as well, making convective initiation less of an issue than previously thought.

I'm not totally buying the GFS yet, as the NAM and ECMWF still don't have the secondary low, but the GFS taken verbatim is pretty potent for central and northern OK into southern KS.

[baroclinic_instability]

Yeah I was kind of figuring this given that the surrounding obs all day have been at least 4 degrees lower. Regardless, the Gulf is basically flowing into the Plains right now.

 

Also, the 00z GFS continues to look nasty on Sunday, the entire cap along the dryline in KS and OK is gone at 21z. I continue to notice a stronger sfc wind response on the GFS compared to the NAM.

 

As is the cap on Monday in OK (very weak to gone).

 

 

The 12Z ECMWF also sides with the GFS, so that's good news for chasers. That said, the NAM tends to do very well (and outperforms the GFS) inside 48 h. The next few model runs will be important WRT Sunday.

 

The cap shouldn't be that much of an issue Sunday seeing that the broad base of the trough implies that the H7 flow advects an EML from NM, as opposed to something thermonuclear from Mexico.

 

GFS indeed backed off its initial simulations, but Sunday still has quite a bit of potential for isolated/discrete supercells along the dryline as the GFS/ECMWF both develop a secondary lee surface cyclone...likely owing to a combo effect of nearly perpendicular cross-barrier flow and diurnal heating over the high plains. The cap is more of a concern than I would have initially thought given the placement of the upper trof...but that is likely due to the first upper wave ejection coming out much faster than initially anticipated. 

[baroclinic_instability]

The GFS has definitely shown a secondary low of sorts further south towards NW OK that really backs the near-surface wind field across much of OK on Sunday.  This results in a rather potent juxtaposition of very unstable CAPE and very high helicity there.  The GFS has also increased the mid-upper level wind fields across OK as well over the past few runs, reflective of its trend towards a deeper trough, and this deeper trough also enhances the synoptic forcing for vertical motion further south as well, making convective initiation less of an issue than previously thought.

I'm not totally buying the GFS yet, as the NAM and ECMWF still don't have the secondary low, but the GFS taken verbatim is pretty potent for central and northern OK into southern KS.

I actually thought the latest GFS runs look less impressive, with more veering (from a dprog/dt sense) than previous runs which were ejecting a weaker initial shortwave into the central plains (in the vicinity of KS/NE)...and therefore veering the flow much less. It seems the first wave coming out of the Rockies will have a much bigger influence than earlier GFS runs were progging.

[KSWx]

GFS indeed backed off its initial simulations, but Sunday still has quite a bit of potential for isolated/discrete supercells along the dryline as the GFS/ECMWF both develop a secondary lee surface cyclone...likely owing to a combo effect of nearly perpendicular cross-barrier flow and diurnal heating over the high plains. The cap is more of a concern than I would have initially thought given the placement of the upper trof...but that is likely due to the first upper wave ejection coming out much faster than initially anticipated. 

 

Would you say it's plausible that we may be looking at the best day today?

[baroclinic_instability]

Would you say it's plausible that we may be looking at the best day today?

It is plausible, absolutely. The whole overall 3-day pattern is fickle to timing of somewhat indistinct waves/lee cyclones which affect both the mass fields and thermodynamics greatly. Even tomorrow has quite a few question marks that simply won't be solved until after the event (backed UL flow, convective blowoff and capping, coverage of DMC along the dryline, etc.). I am not a convective expert, however, and don't pretend to be. But I do think it would be somewhat foolhardy for anyone to say any of the next three days is simply "better" than another, not to mention "better" has different interpretations (which Brett alluded to earlier in his discussion with jojo about coverage and chase potential). The way it looks verbatim, tomorrow does look to have the highest ceiling. I can guarantee (and it is the only guarantee I will make), that at the end of all this, all three days will have yielded some big surprises in some way.

[Chrisrotary12]

In North Platte for the evening.  Will probably be targeting just south and west of here tomorrow.  More south if anything.

[ZackH]

We are also in North Platte... probably going to head for west/central KS... Maybe in an area around Hays to Great Bend. That way we can make a play on whichever target looks best.

[CUmet]

I actually thought the latest GFS runs look less impressive, with more veering (from a dprog/dt sense) than previous runs which were ejecting a weaker initial shortwave into the central plains (in the vicinity of KS/NE)...and therefore veering the flow much less. It seems the first wave coming out of the Rockies will have a much bigger influence than earlier GFS runs were progging.

 

I should specify that it looks better than the runs from 24 or so hours ago, when it looked like the GFS was finally giving into the ECMWF's more strung-out solution.  If you compare with runs from 2-3 days ago, yes it looks somewhat less impressive now.

I still think Sunday clearly has the highest ceiling in terms of impact.  The timing of the jet streak punching through the warm sector is pretty ideal IMO to ensure the faster flow aloft and to minimize the meridional component over a wider area.  If everything goes "right" (note: this is NOT a forecast), I could see a major tornado outbreak, High Risk caliber event for Sunday, whereas the other days I just don't see that possibility.  However, given the differences seen in the NAM and ECMWF vs. the GFS, there's a lot of uncertainty regarding how much of this potential will be realized, and everyone should keep in mind that "ceilings" (if it's even fair to attempt to subjectively determine them) are rarely reached.

[jcwxguy]

Im still debating on gonig to Great Bend to Hays area, as its only 1-2hrs to my west 

[RCNYILWX]

We are also in North Platte... probably going to head for west/central KS... Maybe in an area around Hays to Great Bend. That way we can make a play on whichever target looks best.

00z SPC WRF-NMM looks pretty gnarly for that area 22-02z (http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/00/)

 

 

Rarely see oranges on that output.

[tornadotony]

I actually thought the latest GFS runs look less impressive, with more veering (from a dprog/dt sense) than previous runs which were ejecting a weaker initial shortwave into the central plains (in the vicinity of KS/NE)...and therefore veering the flow much less. It seems the first wave coming out of the Rockies will have a much bigger influence than earlier GFS runs were progging.

Tonight's 00z GFS and last night's are not that much different at all, maybe 5 kt weaker as a whole at 250 hPa and similar 850-hPa and sfc reflections.  If anything, tonight's GFS run has winds slightly stronger and a little more backed at 850 hPa, which will promote better moisture quality near the dryline (this is all for Sunday, of course).  Sunday, with the wind energy in place due to the ejection of the stronger disturbance, by far has the highest potential at this point, IMO, and it's a mighty high ceiling at that.  The 00z soundings from OUN, LMN, and FWD each have major humidity in the low-levels, with hydrolapses located AOA 850-hPa.  That humidity is not going to hocus-pocus mix itself out on Sunday.  With 45-60kt of 0-6km bulk shear with vectors perpedicular to the dryline, 70-80kt of flow at 250 hPa perpendicular to the dryline, 3000-4000J/kg CAPE, large and looping hodographs, a weakening cap, and a shortwave trough disturbance progged to eject over the warm sector on both the GFS and the NAM, Sunday has the potential to be very nasty.  Sunday kinda actually reminds me of 5/24/11 with that sharply negative-tilt trough, only the axis is a bit farther north, eliminating the veer-back-veer issue that actually plagued that outbreak.

[Thundersnow12]

[baroclinic_instability]

I should specify that it looks better than the runs from 24 or so hours ago, when it looked like the GFS was finally giving into the ECMWF's more strung-out solution.  If you compare with runs from 2-3 days ago, yes it looks somewhat less impressive now.

I still think Sunday clearly has the highest ceiling in terms of impact.  The timing of the jet streak punching through the warm sector is pretty ideal IMO to ensure the faster flow aloft and to minimize the meridional component over a wider area.  If everything goes "right" (note: this is NOT a forecast), I could see a major tornado outbreak, High Risk caliber event for Sunday, whereas the other days I just don't see that possibility.  However, given the differences seen in the NAM and ECMWF vs. the GFS, there's a lot of uncertainty regarding how much of this potential will be realized, and everyone should keep in mind that "ceilings" (if it's even fair to attempt to subjectively determine them) are rarely reached.

 

 

Tonight's 00z GFS and last night's are not that much different at all, maybe 5 kt weaker as a whole at 250 hPa and similar 850-hPa and sfc reflections.  If anything, tonight's GFS run has winds slightly stronger and a little more backed at 850 hPa, which will promote better moisture quality near the dryline (this is all for Sunday, of course).  Sunday, with the wind energy in place due to the ejection of the stronger disturbance, by far has the highest potential at this point, IMO, and it's a mighty high ceiling at that.  The 00z soundings from OUN, LMN, and FWD each have major humidity in the low-levels, with hydrolapses located AOA 850-hPa.  That humidity is not going to hocus-pocus mix itself out on Sunday.  With 45-60kt of 0-6km bulk shear with vectors perpedicular to the dryline, 70-80kt of flow at 250 hPa perpendicular to the dryline, 3000-4000J/kg CAPE, large and looping hodographs, a weakening cap, and a shortwave trough disturbance progged to eject over the warm sector on both the GFS and the NAM, Sunday has the potential to be very nasty.  Sunday kinda actually reminds me of 5/24/11 with that sharply negative-tilt trough, only the axis is a bit farther north, eliminating the veer-back-veer issue that actually plagued that outbreak.

 

Certainly not going to argue with either of you guys, I thought the potential was high as well with undoubtedly the best looking hodos above 700 hpa for all three days, I just thought the timing of the lead low was all off, especially with how the lead low affects the mass fields near the developing lee cyclone...as well as weak mass subsidence behind the 300 hpa anomaly reinforcing capping E of the dryline. Either way I won't disagree with the other statements.

[JoMo]

Looks like a 10% hatched tornado area (SAT):