Mid to Late May 2019 Severe Threats

[OUGrad05]

FWIW, the 12 UTC HRRR is pretty much all discrete storm mode.
 

That is downright frightening for Oklahoma

[WhiteoutWX]

Looks like SPC pretty much maintained previous outlook, with some changes mainly to expand the enhanced eastward into Arkansas, with the mention of strong tornadoes possible even into eastern OK and western Arkansas, depending on if convection can initiate there.

[snowlover2]

Moderate risk remains.

Quote

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1229 PM CDT SUN MAY 19 2019  
 
VALID 201200Z - 211200Z  
 
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM NORTHWEST  
TEXAS INTO CENTRAL OKLAHOMA...  
 
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN  
NEW YORK INTO SOUTHERN NEW ENGLAND...  
   
..SUMMARY  
 
SEVERE THUNDERSTORMS CAPABLE OF ALL SEVERE HAZARDS, INCLUDING STRONG  
TORNADOES, ARE EXPECTED ACROSS PORTIONS OF THE SOUTHERN PLAINS ON  
MONDAY.  
 
...SIGNIFICANT SEVERE WEATHER EVENT POSSIBLE ACROSS THE SOUTHERN  
PLAINS ON MONDAY...  
   
..SOUTHERN PLAINS  
 
A COMPLICATED, YET POTENTIALLY HIGHER-END SEVERE WEATHER SCENARIO  
WILL UNFOLD ACROSS THE SOUTHERN PLAINS THROUGHOUT THE FORECAST  
PERIOD. HEIGHT FALLS ASSOCIATED WITH AN APPROACHING LONGWAVE TROUGH  
CENTERED OVER ARIZONA WILL OVERLIE A STRONG SURFACE DRYLINE ALONG  
THE NEW MEXICO/TEXAS BORDER, RESULTING IN A NORTH-SOUTH ORIENTED  
BAND OF STORMS IN THAT AREA AROUND 12Z OR SO. THESE STORMS WILL  
MIGRATE NORTHEASTWARD AND CONTAIN A THREAT FOR HAIL AND DAMAGING  
WIND GUSTS THROUGHOUT THE MORNING DUE TO STEEP MID-LEVEL LAPSE RATES  
AND SUPERCELLULAR WIND PROFILES. A TORNADO THREAT MAY ALSO EXIST ON  
THE SOUTHERN END OF THIS ACTIVITY - ESPECIALLY WHERE CONVECTION CAN  
BECOME SURFACE-BASED AND REMAIN DISCRETE AMIDST WITH SLIGHTLY HIGHER  
BOUNDARY LAYER MOISTURE (I.E., UPPER 60S TO 70S DEWPOINTS).  
 
THE EVOLUTION OF THIS EARLY MORNING COMPLEX WILL IMPACT THE SEVERE  
RISK IN DOWNSTREAM AREAS OF OKLAHOMA AND NORTHWEST TEXAS THROUGH THE  
AFTERNOON AND EVENING. A VARIETY OF OPERATIONAL MODELS AND CAMS  
SUGGEST THAT SOME PORTIONS OF THIS MCS WILL INTERACT WITH THE  
NORTHWARD-MOVING SURFACE WARM FRONT AND POSSIBLY RETARD ITS MOVEMENT  
INTO NORTHERN PORTIONS OF THE OUTLOOK AREA (NEAR THE OK/KS BORDER  
AREA). MEANWHILE, MOST MODEL SOLUTIONS SUGGEST THE DEVELOPMENT OF  
ISOLATED CONVECTION OUT AHEAD OF ANY ONGOING MCS ACTIVITY - WITH  
THIS RISK MOST EVIDENT ACROSS PORTIONS OF SOUTHWESTERN OKLAHOMA AND  
VICINITY. THESE STORMS ARE EXPECTED TO RESIDE IN A ENVIRONMENTAL  
PARAMETER SPACE SUPPORTIVE OF ALL SEVERE HAZARDS, INCLUDING  
SIGNIFICANT HAIL AND STRONG TORNADOES, AND THIS RISK SHOULD BE  
MAXIMIZED AS LONG AS DISCRETE, CELLULAR CONVECTION CAN PERSIST  
THROUGH THE FORECAST PERIOD. THIS RISK WILL BECOME FURTHER ENHANCED  
BY AN INCREASINGLY STRONG LOW-LEVEL JET ACROSS THE REGION DURING THE  
EARLY EVENING SHOULD STORMS MAINTAIN A RELATIVELY DISCRETE MODE.  
 
FARTHER DOWNSTREAM ACROSS EASTERN OKLAHOMA AND VICINITY, UNCERTAINTY  
REMAINS REGARDING SPECIFIC POSITIONING OF THE WARM FRONT, ALTHOUGH  
MOST MODEL SOLUTIONS PERSIST IN DEVELOPING CONVECTION ACROSS THE  
REGION VIA EITHER AN UPSTREAM MCS MOVING INTO THE REGION AND/OR  
ISOLATED CONVECTION FORMING ALONG AND SOUTH OF THE FRONT. THE  
POTENTIAL FOR ISOLATED CONVECTION IS PLAUSIBLE GIVEN SURFACE  
HEATING, WEAK MID-LEVEL INHIBITION, AND BROADLY CONFLUENT  
WARM-SECTOR LOW-LEVEL FLOW - EVEN IN THE ABSENCE OF ANY FORCING FOR  
ASCENT ALOFT. THE ENVIRONMENT ALONG AND SOUTH OF ANY WARM FRONT OR  
CONVECTIVE OUTFLOW WILL SUPPORT ALL SEVERE HAZARDS, INCLUDING STRONG  
TORNADOES. THE INHERITED RISK AREAS HAVE BEEN EXPANDED EASTWARD  
INTO WESTERN ARKANSAS TO ACCOUNT FOR SEVERE POTENTIAL IN THOSE  
AREAS.  
 
NORTH OF THE WARM FRONT (ACROSS KANSAS AND VICINITY), STEEP  
MID-LEVEL LAPSE RATES AND STRONG VERTICAL SHEAR WILL SUPPORT  
PRIMARILY ELEVATED STORMS WITH A THREAT OF LARGE HAIL. STEEP  
MID-LEVEL LAPSE RATES WILL ALSO EXIST IN PORTIONS OF COLORADO,  
ALTHOUGH THE DEVELOPMENT OF ANY SUBSTANTIAL SURFACE-BASED  
INSTABILITY WILL DEPEND ON CONVECTIVE EVOLUTION ACROSS THE TEXAS  
PANHANDLE AND VICINITY. STORMS IN THAT AREA WILL HAVE AT LEAST A  
THREAT FOR LARGE HAIL.  
 
LATE IN THE FORECAST PERIOD (AFTER ABOUT 06Z TUESDAY), AN EJECTING  
MID-LEVEL TROUGH OVER THE FOUR CORNERS VICINITY WILL TAKE ON A  
NEGATIVE TILT WHILE MOVING TOWARD THE HIGH PLAINS. SUSTAINED  
LOW-LEVEL ADVECTION ACROSS THE WARM SECTOR (AND RESULTANT MODERATE  
INSTABILITY) SHOULD RESULT IN DEVELOPMENT OF ANOTHER LINE OF STORMS  
ACROSS THE TEXAS SOUTH PLAINS/PANHANDLE VICINITY. THESE STORMS  
SHOULD REACH THE I-35 CORRIDOR OF OKLAHOMA AND NORTH TEXAS BY THE  
END OF THE FORECAST PERIOD, WITH DAMAGING WIND AND ISOLATED  
TORNADOES REMAINING POSSIBLE.  
   
..MID-ATLANTIC AND NORTHEAST  
 
SURFACE HEATING AHEAD OF AN APPROACHING COLD FRONT NEAR THE  
APPALACHIANS WILL RESULT IN STEEPENING LOW-LEVEL LAPSE RATES AND  
WEAK INSTABILITY. MID-LEVEL LAPSE RATES WILL BE RELATIVELY POOR,  
ALTHOUGH THE GLANCING INFLUENCE OF AN APPROACHING WAVE OVER THE  
EASTERN GREAT LAKES WILL RESULT IN DEVELOPMENT OF A FEW CONVECTIVE  
CELLS ALONG AND AHEAD OF THE FRONT. STRONG FLOW ALOFT AND DOWNWARD  
TRANSPORT OF THAT MOMENTUM NEAR STORMS WILL RESULT IN A FEW DAMAGING  
WIND GUSTS. THIS RISK SHOULD WANE WITH EASTWARD EXTENT IN RESPONSE  
TO NOCTURNAL STABILIZATION.  
   
..MAXIMUM RISK BY HAZARD  
 
TORNADO: 15% SIG - MODERATE  
WIND: 45% - ENHANCED  
HAIL: 30% SIG - ENHANCED  
 
..COOK.. 05/19/2019

 

[jpeters3]

16 minutes ago, snowlover2 said:

Moderate risk remains.

 

I think this discussion hits the forecast problem on head.  There will probably be tornadoes, and even some strong ones.  Details of the outbreak depend on timing of MCS development at various points through the day.  If there is no (or weak) early day MCS, and evening activity can remain discrete, we'll probably see a historic outbreak.  If not, tornado coverage will probably be more sporadic.  If CAMs keep the current trends, I probably wouldn't go with day 1 high risk (at least early tomorrow) given the uncertainty.  

[bjc3395]

At this point - glancing at summary of 12z guidance... I think so long as we don’t get a warm sector crushing MCS... this is bound for a borderline historic outbreak of tornadic supercells. I know that’s crazy to call >24 hours in advance, and I’m by no means saying Dixie level historic. But for plains events, I think we are headed for something very high end.. bordering on history making. CAMs are not built nor able to properly resolve discrete, propagating supercells.. this could easily be a long duration tornadic supercell event across E TX PH into W and C OK, and NW Texas. TTU WRF and NCAR ensembles show a strong signal for discrete modes maintained well after dark - into 5z. Again.. the CAMs you can access for free on pivotal.. especially the 3km NAM.. are not going to resolve tornadic supercells or a discrete fashion for long. 

 

Personally this looks like a pretty prolific event - but the uncertainties as mentioned above preclude a high risk until perhaps even the 10 am update. But I think this is shaping up to be a memorable, long-duration tornado event. 

[WhiteoutWX]

Agreed on not going high until tomorrow morning at the earliest. Gotta see how early morning convection behaves and how far north the warm front makes it.

[jpeters3]

40 minutes ago, bjc3395 said:

At this point - glancing at summary of 12z guidance... I think so long as we don’t get a warm sector crushing MCS... this is bound for a borderline historic outbreak of tornadic supercells. I know that’s crazy to call >24 hours in advance, and I’m by no means saying Dixie level historic. But for plains events, I think we are headed for something very high end.. bordering on history making. CAMs are not built nor able to properly resolve discrete, propagating supercells.. this could easily be a long duration tornadic supercell event across E TX PH into W and C OK, and NW Texas. TTU WRF and NCAR ensembles show a strong signal for discrete modes maintained well after dark - into 5z. Again.. the CAMs you can access for free on pivotal.. especially the 3km NAM.. are not going to resolve tornadic supercells or a discrete fashion for long. 

 

Personally this looks like a pretty prolific event - but the uncertainties as mentioned above preclude a high risk until perhaps even the 10 am update. But I think this is shaping up to be a memorable, long-duration tornado event. 

I wouldn't discount the CAM solutions as much as you suggested.  CAMs generally do a good job of physically resolving the conditions related to the initiation and maintenance of MCSs (this is supported by research).  It is possible that there are subtleties of the dynamics/thermodynamics that the model is capturing that are difficult to pick out of soundings.

[bjc3395]

8 minutes ago, jpeters3 said:

I wouldn't discount the CAM solutions as much as you suggested.  CAMs generally do a good job of physically resolving the conditions related to the initiation and maintenance of MCSs (this is supported by research).  It is possible that there are subtleties of the dynamics/thermodynamics that the model is capturing that are difficult to pick out of soundings.

Not necessarily discounting them but I think we get a long lived supercell event. At least til 3Z. That assumes the front isn’t shunted to ~red river or further south. 

Looks pretty big time. At worst I think we are looking at a mixed mode by 01z or so. We will see. Think we all agree there’s a very high ceiling.. but definitely a low floor too, relative to many expectations. 

 

Another day that has my attention is Wednesday despite rising heights. Seems globals show hints of diurnal CI along the dry line... environment is pretty ripe for tornadic supercells if we pop a few off. 

[WhiteoutWX]

The 18z HRRR scenario would definitely be high risk worthy. Multiple rounds of discrete supercells in an unbelievable environment. Just one model but man that's worrisome for most of Oklahoma if even part of that verified.

[DanLarsen34]

I really feel for anyone who’s responsible for forecasting this event. Seems like the consensus is that tomorrow has a relatively low floor, but extremely high ceiling.

We are talking about a major outbreak with several violent long-track tornadoes IF everything materializes. However, there are still several uncertainties that could significantly mitigate that potential. 

Of course, this hasn’t stopped Mike Morgan from claiming the world is going to end. Even if a set-up looked like April 27 or April 3 the day before, his level of fear-mongering would be completely uncalled for. Here’s the post in question from his twitter account.

[okiestormgeek]

Mike Morgan is infamous for his "drive south" moment that put a lot of people in danger. 

[Quincy]

1 hour ago, WhiteoutWX said:

The 18z HRRR scenario would definitely be high risk worthy. Multiple rounds of discrete supercells in an unbelievable environment. Just one model but man that's worrisome for most of Oklahoma if even part of that verified.

Based on the HRRR:

It starts with West Texas already seeing 3000-4000+ J/kg SBCAPE with minimal CINH by 14z. The low-level jet remains stout, averaging 30-50 knots at 850mb throughout the entire day across the moderate risk area and most of the state of Oklahoma. The shear across Oklahoma would support intense to violent tornadoes, IF storm modes are at least semi-discrete. We’re talking about upwards of 50 knots of 0-1km shear by early afternoon. 

The parameter space moves into a nearly unprecedented categories over west/northwest Texas in the afternoon with 4000-5000+ CAPEs with increasingly intense wind profiles. 

Dew-points of 70 degrees up to I-40, even in the eastern Texas panhandle? 

The HRRR is ominous looking and even if there is some convective contamination, you won’t need much recovery/instability to see numerous intense supercells. 

The instability advertised on the High Plains given the expected wind profiles is extreme and could very well lead to 4”+ hail reports. 

[Indystorm]

I do need to ask from a verification standpoint, how reliable in the past has been the HRRR?

[okiestormgeek]

Which of the models at this point are leaving the door open for a lower-end tornado threat? How has that particular model performed in recent past? Sorry, non-technical  weather geek alert here.

[okiestormgeek]

 

[Quincy]

21 minutes ago, Indystorm said:

I do need to ask from a verification standpoint, how reliable in the past has been the HRRR?

The HRRR, in general, is good with convective evolution and is more conservative with moisture return than the 3km NAM. That’s why I’d take the dew-point progs seriously. They’re fairly close to what the NAM shows. However, this is a complex, multi-round setup. If morning convection evolves differently than progged, that would change how the rest of the day transpires, especially across the northern part of the risk area. 

If the HRRR remains consistent and shows a similar evolution with 00z and subsequent model runs, then confidence will be very high. If the model waffles back and forth, that will speak to the complexity even more. 

As with any convection allowing model, obs and trends will be of the utmost importance. Even if you dial back the HRRR some, it still looks like a tornado outbreak with multiple significant tornadoes is just about unavoidable at this point. There still is a scenario where convective evolution stays messy near/north of I-40, but that’s the best case at this point and probably wouldn’t spare West/Northwest Texas to southwestern Oklahoma. 

[OKStorm]

Area Forecast Discussion
National Weather Service Tulsa OK
251 PM CDT Sun May 19 2019

...Significant severe weather expected Monday with the threat
   for strong tornadoes...

...Flash flooding possible across NE OK Monday/Tuesday...

.DISCUSSION...
Pleasant conditions this afternoon, but this will quickly change
with very active weather anticipated Monday into Tuesday. Potent
upper trough will move out of the desert southwest on Monday. In
response warm front will lift into northeast Oklahoma Monday afternoon.
Along/south of warm front, very unstable conditions expected with
large looping hodographs. Main question at this point is when the
stronger convection develops and how this impacts the northern
progression on warm front. Most CAM solutions have boundary lifting
to at least I-40 and quite possibly to the Oklahoma/Kansas border.
There will be the potential for training supercells near boundary
by Monday afternoon and with limited CIN a few isolated supercells
will also be possible in the warm sector. Given this scenario,
strong/long track tornadoes will be possible with cells that can
remain discrete. In addition, very heavy rainfall is expected with
these storms across northeast Oklahoma with the potential for flash
flooding. A flash flood watch was issued earlier this afternoon
which will be in effect Monday morning through Tuesday afternoon.
Still expect an axis of heavier rainfall that will impact south-
central/southeast Kansas which will likely cause high flows along
the Arkansas river and the Neosho at Commerce.

Main upper storm system will lift northeast into Kansas on Tuesday
with line of strong to severe storms likely sweeping through
eastern Oklahoma Tuesday morning, moving into northwest Arkansas
by early afternoon. Very strong low level wind fields are progged
during this time and even with modest instability, the threat for
QLCS tornadoes/damaging winds are expected, especially east of
highway 75 where the highest instability develops.

Strong upper high builds over the southeast CONUS by mid to late
week. Could still see scattered showers/thunderstorms through the
remainder of the extended periods, mainly across northeast
Oklahoma on the periphery of upper high/stronger southwest flow
aloft.

[lokee]

Significant Flooding Possible Monday into Tuesday...

.Thunderstorms with heavy rainfall will be likely Monday through
early Tuesday, especially from western and central Oklahoma into
northern parts of Oklahoma. While western north Texas and
southeast Oklahoma may not see as long of a duration of heavy
rain, even brief heavy rainfall late Monday and early Tuesday may
lead to flooding and flash flooding.

[Quincy]

Ah, yes. Flooding is another major and perhaps more widespread concern with this system, especially from central/northern Oklahoma into parts of Kansas. 

Not only is Southern California getting an unusual amount of rain this year, but it’s been very wet in the Plains too. (The whole country for that matter as drought areas have been dwindling) 

[yoda]

Moore Public Schools will be closed tomorrow... seeing OKC is closed tomorrow as well

https://mobile.twitter.com/MoorePublicSch/status/1130226134128504832

https://mobile.twitter.com/OKCPS/status/1130228146505232390

[lokee]

28 minutes ago, yoda said:

Moore Public Schools will be closed tomorrow... seeing OKC is closed tomorrow as well

https://mobile.twitter.com/MoorePublicSch/status/1130226134128504832

https://mobile.twitter.com/OKCPS/status/1130228146505232390

Staff have to report in Okcps. So far 5 Okc metro area schools districts are closed to students on May 20th.

[weatherextreme]

1 hour ago, okiestormgeek said:

Mike Morgan is infamous for his "drive south" moment that put a lot of people in danger. 

 

 

[weatherextreme]

1 hour ago, DanLarsen34 said:

I really feel for anyone who’s responsible for forecasting this event. Seems like the consensus is that tomorrow has a relatively low floor, but extremely high ceiling.

We are talking about a major outbreak with several violent long-track tornadoes IF everything materializes. However, there are still several uncertainties that could significantly mitigate that potential. 

Of course, this hasn’t stopped Mike Morgan from claiming the world is going to end. Even if a set-up looked like April 27 or April 3 the day before, his level of fear-mongering would be completely uncalled for. Here’s the post in question from his twitter account.

More.

 

Mike Morgan‏Verified account @MikeMorganKFOR 31m31 minutes ago

More

5PM Sun. UPDATE: 1. Never seen OKC METRO under CONTINUOUS tornado threat this long: literally 1PM-1AM.

2. Multiple tornado strikes Metro quite possible.

3. Large/violent tornadoes are possible.

4. SVR flooding possible. To avoid hyperbole, first Okla. WX report below #okwx @kfor

[jojo762]

2 hours ago, Indystorm said:

I do need to ask from a verification standpoint, how reliable in the past has been the HRRR?

On Friday it nailed the SW NEB tornadic supercell pretty well. Also showed some convection along the DL in KS (it did fail to maintain it though). Imo it’s probably been one of the better models lately when it comes to evolution. Of course it has its own issues with over convecting sometimes.

 

EDIT: tomorrow probably isn’t a case of overconvecting by any means though.

[lokee]

Warm front is along the red river at 10am in this run of the HRRR.

[Benadrill]

1 hour ago, yoda said:

Moore Public Schools will be closed tomorrow... seeing OKC is closed tomorrow as well

https://mobile.twitter.com/MoorePublicSch/status/1130226134128504832

https://mobile.twitter.com/OKCPS/status/1130228146505232390

I had no clue tornado days were a thing.  I grew up praying for snow days.  

[Travisstorma]

They weren't when I was in school. 

[lokee]

After the Moore tornado that took the lives of the students in Moore schools are becoming more proactive.

[janetjanet998]

17 minutes ago, Benadrill said:

I had no clue tornado days were a thing.  I grew up praying for snow days.  

I see pros and cons...

a lot of schools got hit in the 1974 super outbreak and the recent OKC outbreaks....a bit of bad luck and a large group and kids could be  in danger..plus school buses out 3-4pmish

on the other hand a newer built school is more sturdy then a home and much better then a mobile home ...plus a lot of parents work and its hard to find day care on short notice ...so early teen  aged kids might be home  alone even watching their younger siblings without adult supervision in trailers or flimsy homes 

 

 

 

[Benadrill]

Just now, janetjanet998 said:

I see pros and cons...

a lot of schools got hit in the 1974 super outbreak ....a bit of bad luck and large group and kids can get put in danger..plus school buses out 3-4pmish

on the other hand a school is more sturdy then a home and much better then a mobile home ...plus a lot of parents work so early teen kids might be home  alone even watching their younger siblings 

 

 

 

I'm not hating on it. I think it's a good idea. For some reason the schools in that area don't seem to have basements even though it is a prime area for tornadoes? And the school bus hazards.