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OKTWISTER

Severe Weather May 4th

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Small set up for tomorrow in NE OK and SW Mo to NW AR, currently we have a cold front draped across NE OK that is forecast to move back north. Dew points have been high today just muggy outside. Wind and hail are the main threat but NWS Tulsa and SPC mention tornadoes and Day 2 is up to 5% area.  Could be a sleeper day and I would not be surprised to see a upgrade to Enhanced tomorrow. 

current.TDEW.grad.png

SEVERE TSTORM Threat Mon

Max Hail Size Mon

day2probotlk_1730_torn.gif

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Models right now are pretty inconsistent with hodographs and a few other parameters.  RAP looks like we'll get an upgrade to 10% tor, NAM looks like an absolute mess with all kinds of VB and lack of flow at 850 and 700.  Hopefully we have a better handle on it by in the morning.  I definitely think we could get an ENH upgrade, may be for hail but we'll see tomorrow.  

I also agree could be a sneaky day especially with this sfc low off to the west.  

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Haven’t looked at tomorrow in depth yet, but today definitely over performers in SWMO. Hoping the same doesn’t happen tomorrow, may 4 has enough tornado history around these parts. 

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A quick and dirty comparison shows some similarities to 4/28 and almost in the same area. There might be slightly longer residence time for discrete storms this go around. 

Could have another SE to S moving tail end Charlie in the central Oklahoma vicinity.

There’s also a signal for morning convective activity, a storm cluster or even an MCS dropping from northern Kansas toward the Ozarks. Wonder if that may shunt the front farther south and/or reintensify across Missouri.

Currently wrapping up a chase in Nebraska. I’ll take a closer look in a couple of hours. 

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00z RAP verbatim show a high-end parameter space developing across SE KS/NE OK by as early as 20z tomorrow. CAMs provide a mixed bag of results for tomorrow, most which do not exactly show a high-end setup like the RAP -- especially with regard to convective evolution during the morning/afternoon and into the evening... but we'll have to see.

00z NAM also shows a higher-end parameter space developing, but with more capping in the afternoon prior to 00z... Somewhat concerned about lackluster low-level lapse rates, but we'll see how that evolves.

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I don’t really have too much to add. Looks like a one-two punch. Morning/early afternoon hailers from northeastern KS into MO, then watch the front/trough unzip by 21-23z from SW MO into OK. HRRR showed some steep low-level lapse rates, but 0-3km CAPEs may be limited with southwest extent. 

Biggest question in my mind is storm mode in Oklahoma. CAPE/shear will be there. Deep shear vectors probably favor mixed modes and a few supercells, but how long can storms stay discrete? We’ll see. 

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9 hours ago, jojo762 said:

00z RAP verbatim show a high-end parameter space developing across SE KS/NE OK by as early as 20z tomorrow. CAMs provide a mixed bag of results for tomorrow, most which do not exactly show a high-end setup like the RAP -- especially with regard to convective evolution during the morning/afternoon and into the evening... but we'll have to see.

00z NAM also shows a higher-end parameter space developing, but with more capping in the afternoon prior to 00z... Somewhat concerned about lackluster low-level lapse rates, but we'll see how that evolves.

Yeah the RAP yesterday was impressive the NAM was absolute trash.  I went to bed before the 00Z was available.  I haven't looked at much this morning, just finished my workout and need to knock out a few things for the office then I'll start digging through the models.  

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I am curious how the storms this morning affect the evolution of the afternoon/evening event. Will be interesting to watch. May 4th is a dirty word around here when you couple it with severe weather. 

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10 minutes ago, Wx 24/7 said:

I am curious how the storms this morning affect the evolution of the afternoon/evening event. Will be interesting to watch. May 4th is a dirty word around here when you couple it with severe weather. 

In OK they appear to be elevated SVR hailers so boundary layer will probably stay intact?  Plus its early, sun is out, I'd expect a capping inversion to develop by mid/late morning?  

If that doesn't occur and we remain uncapped it'll be a convective mess much of the day.

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Main differences between today and the 04/28 event last week appear to be slightly better low-level shear today with winds staying a bit more backed ahead of the dryline/cold front, but also a stronger cap and less synoptic scale lift as the upper wave is further removed to the north. Also, the boundary-relative cloud layer flow is a bit more parallel to the boundary today so storms *may* try to go upscale a bit more than last week, although the stronger cap could work to counter that. 

Overall I'd say tornado potential is slightly higher today owing to the better shear, but very conditional given capping, weaker low-level CAPE, questions on storm mode. 

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If this morning is any indication, we could have some massive hail later today. 

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Morning storms exiting NE Oklahoma are near an effective warm front. Elevated instability exists to the NE, while most surface-based instability is SW. 

Note that the 700mb thermal ridge is over western OK at the moment. As it shifts east, storms lift into/through Missouri and capping takes over.

Morning storms have little to no impact on mid/late afternoon activity. Unless there’s some outflow boundary... Let’s say that scenario doesn’t reduce the severe threat. 

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13 minutes ago, Quincy said:

Morning storms exiting NE Oklahoma are near an effective warm front. Elevated instability exists to the NE, while most surface-based instability is SW. 

Note that the 700mb thermal ridge is over western OK at the moment. As it shifts east, storms lift into/through Missouri and capping takes over.

Morning storms have little to no impact on mid/late afternoon activity. Unless there’s some outflow boundary... Let’s say that scenario doesn’t reduce the severe threat. 

Agreed sir.  
Also, as mentioned above SFC backing is higher than was forecast yesterday.  Haven't pulled models yet, busy working so I can chase this afternoon but a quick glance at the mesonet has me thinking tor threat may turn out to be a bit higher than the 5% currently forecast.

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12z CAMs seem to be extremely consistent with their respective 00z runs, CI/placement wise. Maybe a very slight nudge eastward with the westward edge of the CI. Going to be close for OKC metro but consensus suggests the front will be fast enough to push through before significant CI. Although the two events aren't the exact same, may be worth noting that CI occurred a little further west and was more widespread than CAMs suggested on 04/28. With stronger capping today though, I'd be more inclined to agree with the CAMs and say this should be mostly confined to east of I-35, south of I-44. 

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17 minutes ago, WhiteoutWX said:

12z CAMs seem to be extremely consistent with their respective 00z runs, CI/placement wise. Maybe a very slight nudge eastward with the westward edge of the CI. Going to be close for OKC metro but consensus suggests the front will be fast enough to push through before significant CI. Although the two events aren't the exact same, may be worth noting that CI occurred a little further west and was more widespread than CAMs suggested on 04/28. With stronger capping today though, I'd be more inclined to agree with the CAMs and say this should be mostly confined to east of I-35, south of I-44. 

This. Watch temperature trends closely. HRRR is not far off as of 15z, just 1-2F too cool in parts of central OK. However, it may only take an extra degree or two of heating to break the cap. That’s what we saw happen on 4/28. 

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7 minutes ago, Quincy said:

This. Watch temperature trends closely. HRRR is not far off as of 15z, just 1-2F too cool in parts of central OK. However, it may only take an extra degree or two of heating to break the cap. That’s what we saw happen on 4/28. 

There's still some small but significant differences in the modeling of the SFC low, especially this afternoon between 3 and 6pm.  That will have a huge impact on the populations impacted by the storm and the probs of tors.  RAP is still showing some damn impressive hodographs over a decent chunk of eastern OK primarily north of 40.  The HRRR has a touch more surface veering due to placement to the L and shear isn't quite a good.  I haven't chased each model run but since yesterday afternoon the RAP seems to be holding pretty steady with HRRR and NAM drifting that direction a bit.  

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SPC upgraded to 10% hatched TOR risk across SE KS/NE OK/SW MO. Ingredients appear to be coming together for a potentially significant day across this region.

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5 minutes ago, jojo762 said:

SPC upgraded to 10% hatched TOR risk across SE KS/NE OK/SW MO. Ingredients appear to be coming together for a potentially significant day across this region.

Yeah I agree, I can't see the update but was commenting to a buddy and put on my FB page I expect an upgrade to 10%.  Not sure why I can't see it.  

Claremore to Joplin to Springfield could have one or two strong tors today, perhaps a touch more with the triple point setting up the way it is.  Don't want to hype but this is starting to get very interesting, especially with the better than forecast shear and solid sfc backing along and east of US169

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This is from the outlook regarding the area of focus for a tornado threat 

...OK/KS/MO/AR/TX this afternoon and evening...
   Latest surface analysis shows a low over northwest OK with the
   dryline extending southward into western north TX.  This dryline
   will surge eastward today as a cold front sags across KS into OK. 
   Current indications are that the triple-point of the cold front and
   dryline will be over far northeast OK by late afternoon.  There is
   also a subtle warm front extending from northeast OK into central
   AR.  This boundary will lift slowly northward as well.  The result
   will be a zone of low-level convergence and rapid thunderstorm
   development in the 3-5pm period over extreme southeast KS, northeast
   OK, and southwest MO.  These storms will be in an environment of
   very high CAPE values, steep mid-level lapse rates, and ample
   deep-layer shear to support supercell structures.  Low-level shear
   profiles will also be very strong - especially in vicinity of the
   warm front where backed surface winds will enhance 1km helicity
   values over 500 m2/s2.  Storms that form will pose a risk of very
   large hail and a few tornadoes (including strong tornadoes).  The
   primary negative factor for tornado risk is the linear forcing
   mechanism along the cold front, which may result in undercutting and
   a transition to linear storm structures within a couple of hours of
   initiation.  This activity will likely spread east-southeastward
   across northern AR after dark with a hail/wind and isolated tornado
   risk.

   Farther south along the dryline and cold front, storms should
   develop through the late afternoon and evening across the eastern
   half of OK and perhaps into north TX.  Very large hail is the
   primary risk with these storms.

Mentions the somewhat quick transition to a linear mode being a possible limiting factor to the tornado threat, which might have been discussed here(?), ingredients look impressive though.

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The springfield Metro area continues to be socked in clouds. Unless that changes in the next hour or so, I dont see what of a tornado threat here. Further west, and southwest, it could be a different story. Temps in the Upper 50's, dews in the mid 50's, i just dont see how it happens here unless something drastically changes soon. 

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As of 18z low-level lapse rates were anemic from far northeastern OK into southwestern MO. There still is some time to heat, so we’ll see... 

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3 minutes ago, Quincy said:

As of 18z low-level lapse rates were anemic from far northeastern OK into southwestern MO. There still is some time to heat, so we’ll see... 

A couple hours left to warm up still...

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1 minute ago, OUGrad05 said:

A couple hours left to warm up still...

Just ran back three runs to 15z and HRRR was progging 6.5-7 C/km LLLRs where the 18z run at hour 1 has 5.5 C/km... Definitely trending down, but there still is some time. 

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Pretty ugly and satellite shows thick cloud deck, particularly across the Missouri side of the 10% hatched. 

 

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Just now, yoda said:

SPC MCD seemed to be suggesting the opposite... saying TOR watch will be needed soon for the areas you are discussing

That doesnt necessarily mean at 10% hatched risk will be realized. SWMO makes up roughly half of the 10% area, and remains locked in clouds.  

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1 minute ago, MUWX said:

That doesnt necessarily mean at 10% hatched risk will be realized. SWMO makes up roughly half of the 10% area, and remains locked in clouds.  

Perhaps... but MCD disco does say risk of strong tornado in it for SW MO

 

Mesoscale Discussion 0531
   NWS Storm Prediction Center Norman OK
   0121 PM CDT Mon May 04 2020

   Areas affected...Northeast Oklahoma...southeast Kansas...southwest
   Missouri...northwest Arkansas

   Concerning...Severe potential...Watch likely 

   Valid 041821Z - 042015Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Initially cellular thunderstorm development along a
   pre-frontal wind shift is likely within 2-3 hours. These storms will
   quickly become severe and be capable of all severe hazards. A strong
   tornado will be possible near the KS/MO/OK/AR border region where
   low-level hodographs are more favorable. A tornado watch will be
   needed within the next couples of hours.

   DISCUSSION...Ahead of a southward moving cold front, cumulus clouds
   have begun to become increasingly agitated within a zone of upper
   60s F dewpoints in the northeast Oklahoma vicinity. Current
   observations indicate that the likely zone of initiation will be
   along the pre-frontal wind shift. With 1500-2500 J/kg MLCAPE and
   45-60 kts of effective shear, the initial storms that develop are
   likely to be supercells capable of large/very large hail,
   strong/severe wind gusts, and a few tornadoes. An area of enhanced
   low-level veering, observed in KSGF/KINX VAD data, is present along
   and near the warm front placed near the OK/AR/MO/KS border region. A
   strong tornado or two will be possible in this region. One
   uncertainty is how quickly the cold front will undercut initially
   cellular activity as it has reached the south-central
   KS/north-central OK border. With surface observations showing a
   deepening surface cyclone in central OK, it is possible that the
   eastern portions of this front in southeastern KS will slow its
   progression and allow for a longer window of opportunity for
   tornadic activity. With storm initiation likely within the next 2-3
   hours, a WW will be needed within the next couple of hours.

   ..Wendt/Hart.. 05/04/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...SGF...TSA...ICT...

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