Mid to Late May 2019 Severe Threats

[yoda]

Just now, Natester said:

45% tornado potential hatched introduced in the most recent outlook.  First time since 4/14/12.

[Upper Level LOL]

This day has continually trended up within the last 48 hours or so. Now we just wait to see what convects and how quickly it spins.

[DanLarsen34]

These model runs are just unreal. Everything’s converging on this being an outbreak for the history books. This screen shot looks like a radar grab from the super outbreak in 2011. 

[Eskimo Joe]

2 hours ago, mappy said:

you should follow Mike Morgan, he comes up with his own F-scale ratings ahead of time too

OMG what a Class 1 kook.  Wow.  

[Roger Smith]

1 hour ago, jimrunsfar said:

How concerning/relevant is this apparent clearing back in West Texas?

The main significance of that clearing would be that it allows rapid heating of the surface layers in the warm sector developing over a region south of Lubbock TX.

Perhaps more ominous is the clearing in east central NM on your image, that represents the zone between the cold front (currently lying across s.e. NM into far western panhandles of TX and OK) and the eventual dry line feature. 

In this set-up, what normally happens is that the cold front becomes the focus for some supercell development by mid-afternoon, with the dry line accelerating and catching up to it, causing explosive development. Either the dry line becomes a primary focus for severe storms by the peak stages (which I think will be quite late in the day given the dynamics) or the dry line essentially merges with the cold front with the same result. 

Looking at the current guidance, the dry line will likely form over eastern NM by about 20z with the cold front approaching an AMA-LBB-MAF line. Then both will accelerate east but the dry line looks likely to be sweeping through the TX panhandle to reach western OK by 03z with the cold front then only 50-100 miles east of it. Would suggest that the result will be two lines of supercells, the first one associated with cold front having more development into the Wichita Falls to Abilene region compared to the dry line where the development may cut off a bit further north (Childress possibly). 

Meanwhile some severe storms will form out ahead of all that near the warm front which looks likely to stall near the OK-KS border and rotate slowly north into south central KS. 

My guess as to most severe potential would be Lubbock to Clinton OK. 

============================================================

Here's a rough graphic of the air mass boundaries to be expected and the air mass characteristics ...

valid for late afternoon with maximum heating potential realized. 

 

COOL DRY AIR MASS... DL .. P .... CF ... mT

temps 65-72 ..........// .. 85-95 .. // ..... 83-88

dp 20-30   .......... // .. 50-60 .. // ..... 70-75

 

So in that schematic you have the dry line, P for "polar" air mass (an old term, think of it as Pacific origin transitional air mass that can be quite warm under subtropical sun angles) then the cold front (CF) and the mT (maritime tropical) air mass (moist Gulf air now in place over most of TX and OK). The P sector between the tropical air and the cooler air with much lower dew points (Ruidoso NM already has dew points below 20 F) will become very windy by afternoon (WSW 40G60) with winds in the warm sector continuing more like SSW 20-30. 

Every actual situation has its own little variations from this sort of statistical average. In today's outbreak, what I noticed was that the upper dynamics become much stronger in the interval from 00z to 06z, with the upper level low crossing most of NM in that time frame and forcing the dynamics ahead to become more ominous. So once the daytime heating cycle comes to a close, this situation will actually be ramping up (something like this happened with the Goodland KS event) and the peak will likely be after dark. Rather than southwest KS in this case I would flag the western third of OK, eastern half of TX panhandle and some adjacent parts of TX around Wichita Falls for the most damaging storm potential. Let's hope they stay over open country. 

[RyanDe680]

Incredible set up forming.  Enthusiast optimism at an all time high with hopes of minimal danger to life, but with PDS already coming out, not looking good.  Stay safe.

 

[Calderon]

8 minutes ago, Eskimo Joe said:

OMG what a Class 1 kook.  Wow.  

Eh, the wording is funky with that. He does say what it could potentially be with radar and his own very long visual experience. That said, whoever said David Payne doesn't do that must forget about his days as a chaser for KFOR and he's said it a couple times at KWTV also. 

They both need to knock that crap off. 

[Eskimo Joe]

New Flood Watch from OUN really ups the wording:

Quote

Flood Watch
National Weather Service Norman OK
1142 AM CDT Mon May 20 2019

...Life Threatening Flood/Flash Flood Episode Possible Monday
into Tuesday...

.Thunderstorms with heavy rainfall will become widespread Monday
through Tuesday afternoon, especially over western, northern, and
central Oklahoma. The potential for extremely dangerous and life
threatening flooding and flash flooding will exist by this evening/
overnight through Tuesday. Multiple severe weather hazards will
be present today. Now is the time to develop a tornado safety plan
that does not include sheltering in flood prone areas!

 

[Natester]

Warm front currently south of OKC.

 

[DanLarsen34]

Hey guys. A May 20 thread is up now on the forum if everyone wants to jump over there.

[Drz1111]

4 minutes ago, Natester said:

Warm front currently south of OKC.

 

I don't think that's right.  Its more like an outflow boundary or something. Dew is at 64 in OKC.

[dan11295]

Important to emphasize not sheltering in flood prone locations like drainage ditches. This was a problem in OKC metro during the El Reno event in particular, IIRC.

 

EDIT: Just looked up the NWS OUN page on that event. There were 13 flooding fatalites (12 in OKC) during that event.

[Calderon]

3 minutes ago, Drz1111 said:

I don't think that's right.  Its more like an outflow boundary or something. Dew is at 64 in OKC.

No, it's correct. The warm front, per that image, was between OKC and Chickasha. An outflow boundary would NOT have an easterly wind component. 

[Natester]

Warm front possibly over OKC right now per this image.

[Drz1111]

4 minutes ago, Calderon said:

No, it's correct. The warm front, per that image, was between OKC and Chickasha. An outflow boundary would NOT have an easterly wind component. 

I don't agree with that - that's an oversimplification when all these boundaries are interacting.

[NaoPos]

 

[pbrussell]

Kind of wish there weren’t two different threads ongoing with this event. It’s already hard enough to keep up with what’s unfolding. Regardless, folks may consider moving to the new thread to consolidate things. I know I don’t want to be flipping back and forth three hours from now 

[Calderon]

4 minutes ago, Drz1111 said:

I don't agree with that - that's an oversimplification when all these boundaries are interacting.

Okay, then what else would it be? Winds ahead of the warm from have been easterly, for well over 4 hours and now they've become southeast and DP and temp is rising more. I've kept a close eye on the Mesonet, and the warm front is spot on where I said it was last hour and has progressed a little farther north since.

Sometimes the simplest answer is actually the right one.

[Eskimo Joe]

Folks, please use this thread for today:  

 

[Chinook]

As for tomorrow (5/21), convection- allowing models all have an intense north-to-south squall line tracking near Springfield, Joplin, Fayetteville, AR. Model soundings show a maximum of 2000 - 2500 J/kg of CAPE east of this line, and also show, 350 m2/s2 of SRH, and over 60 kt of deep-layer shear. Shear values are definitely much higher than normal. There may be tornadoes within the squall line.

[Chinook]

Went back to CIPS analogs, 5/19, forecast hour 36 (valid 5/20) 

Interesting analogs. Several show significant severe. Best analog Apr, 9, 2008. (see lower image)

 

[Quincy]

Agree with the prospects for a squall line with embedded tornadoes tomorrow. There could be a few left-moving, transient supercells in the Kansas vicinity around the upper level low, but it doesn't look like either area is worth a drive for chasing prospects.

It looks like any more substantial Plains severe threats this week may not be until Thursday, although it is possible that a few widely isolated storms might initiate on Wednesday.

[KSWx]

That tornado warned storm for North Tulsa has quite an inflow notch right now. Terrible timing considering how many are likely commuting.

 

Edit: Tornado confirmed.

 

[Brick Tamland]

The tornadoes are continuing this morning in OK. Great scanner feed here from Bryan County, OK.

 

https://www.broadcastify.com/listen/feed/14040/web

[jojo762]

Considering chasing today in central KS, given relatively proximity to me... but 60+mph storm motions and 100kt cloud-bearing shear tearing apart updrafts might keep me away. 

[Brick Tamland]

I wouldn't sleep on today, either. Looks like AR and MO are under the gun.

 

 

Mesoscale Discussion 0722
NWS Storm Prediction Center Norman OK
0957 AM CDT Tue May 21 2019

Areas affected...Western AR and southern MO

Concerning...Severe potential...Watch likely 

Valid 211457Z - 211630Z

Probability of Watch Issuance...80 percent

SUMMARY...A pre-frontal squall line will spread eastward and
northeastward into western Arkansas and southern Missouri through
late morning and early afternoon. Destabilization northward in
advance of the line will support a continued threat for a few
tornadoes with embedded circulations.

DISCUSSION...A pre-frontal squall line is moving eastward from
eastern OK toward western AR. As a pronounced upstream shortwave
trough begins to eject northeastward from northwest TX and western
OK, an associated surface cyclone will develop northeastward into
KS. The near-surface layer is still stable into southern MO per
surface observations and a 14z SGF sounding. However, the surface
warm sector will spread northward from AR into MO through the
afternoon, as the environment becomes more supportive of
surface-based convection into MO through the afternoon. Strong
deep-layer south-southwesterly vertical shear will support embedded
bowing segments and/or rotating storms within the convective line
into the afternoon. Given strong low-level shear and a moist
environment, there will continue to be a threat for occasional
tornadoes with embedded circulations in the line, as well as
damaging gusts and isolated large hail. The storms will progress
east of tornado watch 205 in the next 1-2 hours, necessitating a new
tornado watch into AR and MO after 16z.

..Thompson/Hart.. 05/21/2019

[Santa Clause]

Qlcs Tors are way to go to this year it seems.

[Brick Tamland]

There's the watch.

 

[Chinook]

Today, some models have over 800 m2/s2 of 0-3km SRH in front of the squall line in Missouri. You don't see that very often with surface-based instability.

 I saved this image at 01z. I thought this might be fun. For most areas in Oklahoma, SCP values were about 33, and STP values were about 9-10.

 

[StormChazer]

We gonna talk about this tomorrow? SPC has a marginal risk of severe storms tomorrow, but I'd argue this requires a slight to enhanced,