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May 16th Severe Potential


Jim Martin

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Yeah... even the GFS has trended toward this being "meh."

 

Er, the 12z and 18z GFS still showed a substantial threat. The thing that will most likely make or break this is the strength of the lead southern stream shortwave. That eastern troughing might actually help to a degree in shearing that wave out if it is weak enough.

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Er, the 12z and 18z GFS still showed a substantial threat. The thing that will most likely make or break this is the strength of the lead southern stream shortwave. That eastern troughing might actually help to a degree in shearing that wave out if it is weak enough.

Agreed, I'm also a bit concerned that this current front may knock moisture back more than estimated at the moment.  

All of these issues will become much clearer over the next 48 hrs.

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Er, the 12z and 18z GFS still showed a substantial threat. The thing that will most likely make or break this is the strength of the lead southern stream shortwave. That eastern troughing might actually help to a degree in shearing that wave out if it is weak enough.

Not a big fan of the wind fields before 00Z anymore... Which as we've seen recently, can be a big problem. Any appreciable tornado threat would be relatively limited to a few hour time frame, but maybe I just am having too high of expectations... Funny thing is-- at this time-- it looks like any "main threat" area would be over W OK, which is notorious for terrible busts, as I believe Brett has said many times.

 

But yes, near and after 00Z, the severe threat-- as shown on the GFS-- would ramp up quite a bit... Main question would be if you could get storms to remain supercellular that long, or if initiation will occur late enough for that not to matter.

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Not a big fan of the wind fields before 00Z anymore... Which as we've seen recently, can be a big problem. Any appreciable tornado threat would be relatively limited to a few hour time frame, but maybe I just am having too high of expectations... Funny thing is-- at this time-- it looks like any "main threat" area would be over W OK, which is notorious for terrible busts, as I believe Brett has said many times.

 

But yes, near and after 00Z, the severe threat-- as shown on the GFS-- would ramp up quite a bit... Main question would be if you could get storms to remain supercellular that long, or if initiation will occur late enough for that not to matter.

 

It's a low amplitude feature, there probably wouldn't be a lot of linear forcing going on here. There are other things, such as unforeseen low level backing (see 5/9), that can augment low level wind profiles earlier on assuming there isn't a wholesale issue with the wind profile (see the splitting cells on 5/8).

 

Global models are often not as adept at picking out mesoscale features/influences that may cause some of these caveats (be it positive or negative for a setup) because of their resolution. Their grid-spacing does not allow for that since what happens on a sub-grid scale must be parameterized.

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I'm still licking my wounds for missing out this past Monday due to a final exam that day, so I'm really hoping next Monday delivers. My biggest concern at the moment probably stems from the lead wave potentially causing the low level jet to veer too far to the east. The last few GFS runs have looked nice as mentioned above and the ECMWF has been trending a little nicer, but there is still so much that could potentially go wrong at this range, so it probably best to not get too caught up yet.

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You're kidding, right?

As said its a lower solitude wave with great shear IMO.

low-level wind fields before 00Z specifically. Not mid-upper level/deep-layer shear. I'm not going to be too excited about this until there is at least some semblance of model agreement on at least a decent threat. Given that we are now less than 5 days out and we still have almost everything vs. the GFS, I have very little confidence in much of anything. Still could produce a big day but the large amount of warm sector crapvection on all the models hampers my excitement a bit.
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wow, tonight's NAM and GFS both have highs in central OK on Sunday in the low 50s.

And the 50 dew point contour at 12z Monday is south of the Red River.

That's a LOT of recovery needed in a few short hours during Monday.

huh? The 60 DP isodrosotherm on the GFS at 12z Monday is at the red river, and it shows mid/upr 60s to the KS/OK border by 00Z. NAM however does have the 60 and 50-degree isodrosotherm much further south.

GFS continues to look potent for Monday, maybe a tad further west than what it was previously showing. Interested to see what the other 00Z mid-range guidance looks like.

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    yes, was looking at the NAM for the Monday morning dew points.

 

    still think that the GFS recovery during Monday is awfully aggressive, but it is mid-May....

 

 

huh? The 60 DP isodrosotherm on the GFS at 12z Monday is at the red river, and it shows mid/upr 60s to the KS/OK border by 00Z. NAM however does have the 60 and 50-degree isodrosotherm much further south.

GFS continue to look potent for Monday, maybe a tad further west than what it was previously showing. Interested to see what the other 00Z mid-range guidance looks like.

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The differences in moisture between the 12Z GFS and 12Z NAM for 00Z Tuesday is astounding.  The NAM struggles to get 60* dews up to I40 while the GFS pushes them all hte way north to the OK/KS border.  GFS paints most of OK under the warm sector with 65-69* dew points...

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At first glance...12z GFS has sort of breathed new life into this setup (or, at least, it has stepped it up a bit).

Will need to look more but I'm more impressed with 12z GFS than any other run so far. NAM has adjusted some but not too much, though I have to side more with the GFS depiction as the time of year would favor it. OUN and spc favor the front being lifted further north as well.

GFS steps up the shear some.. nice to see as prior runs were well short of impressive in my mind.

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At first glance...12z GFS has sort of breathed new life into this setup (or, at least, it has stepped it up a bit).

Will need to look more but I'm more impressed with 12z GFS than any other run so far. NAM has adjusted some but not too much, though I have to side more with the GFS depiction as the time of year would favor it. OUN and spc favor the front being lifted further north as well.

GFS steps up the shear some.. nice to see as prior runs were well short of impressive in my mind.

 

Actually, I'd have to admit that the 12z NAM adjustment of the WF position is pretty big. It leaped northward toward the GFS solution near the OK/KS border, though it's not all the way there yet. Regardless, it puts the E TX PH into W OK in play, where bulk and low-level shear are sufficient to make things more interesting than S of the Red River.

 

The GFS is still pretty much alone in cranking up a strong (>30 kt) LLJ by 00z Tue. Interestingly, though, even the NAM has so much turning in the lowest 3 km AGL that SRH is impressive right along the dryline. Favorable hodographs right at initiation can be a big plus, as we were reminded last Sun vs. Mon. *If* the WF actually lifts near or past the KS border, another aspect of this setup I like is that even if morning storms and cloudcover breed capping concerns with eastward extent (similar to last Sun), storm motions should be much slower on Monday - leading to longer storm residence times in the instability axis.

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At first glance...12z GFS has sort of breathed new life into this setup (or, at least, it has stepped it up a bit).

Will need to look more but I'm more impressed with 12z GFS than any other run so far. NAM has adjusted some but not too much, though I have to side more with the GFS depiction as the time of year would favor it. OUN and spc favor the front being lifted further north as well.

GFS steps up the shear some.. nice to see as prior runs were well short of impressive in my mind.

yeah the NAM moved the WF more northward than previous runs, LLJ is not that impressive really though... Still disagrees quite about with the GFS about how the TX panhandle will pan out.
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At first glance...12z GFS has sort of breathed new life into this setup (or, at least, it has stepped it up a bit).

Will need to look more but I'm more impressed with 12z GFS than any other run so far. NAM has adjusted some but not too much, though I have to side more with the GFS depiction as the time of year would favor it. OUN and spc favor the front being lifted further north as well.

GFS steps up the shear some.. nice to see as prior runs were well short of impressive in my mind.

Last few runs were lacking on shear...its up some, still not great over most of western OK.

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Actually, I'd have to admit that the 12z NAM adjustment of the WF position is pretty big. It leaped northward toward the GFS solution near the OK/KS border, though it's not all the way there yet. Regardless, it puts the E TX PH into W OK in play, where bulk and low-level shear are sufficient to make things more interesting than S of the Red River.

 

The GFS is still pretty much alone in cranking up a strong (>30 kt) LLJ by 00z Tue. Interestingly, though, even the NAM has so much turning in the lowest 3 km AGL that SRH is impressive right along the dryline. Favorable hodographs right at initiation can be a big plus, as we were reminded last Sun vs. Mon. *If* the WF actually lifts near or past the KS border, another aspect of this setup I like is that even if morning storms and cloudcover breed capping concerns with eastward extent (similar to last Sun), storm motions should be much slower on Monday - leading to longer storm residence times in the instability axis.

 

The 12z Euro also jumped north..looks like a little stronger flow at H5 too

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18z NAM is pretty explosive near the WF in the E TX Panhandle and W OK, especially in the lowest 3 km. The amount of low level turning in that vicinity is amazing. Might just take 30 kts at H85 there with that degree of veering with height in the low levels (although stronger would be appreciated to strengthen the 0-1 km SRH values/speed shear).

 

Like Brett said, one of the first things I noticed with this when the GFS began to show it was that the storm motions here are not ripping like we saw on 5/8, so these storms should have a decently long residence time to work with.

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Headed back from the Twister meseum party in Wakita and checked on this thread to see how Monday looks. Glad to hear it is starting to trend upwards. I'd love to have another Panhandle TOR day. Nothing against Southwest OK but I'm tired of dealing with that stupid mountain and wildlife preserve. It's the year of mesoscale accidents it seems so I'll be paying attention to any of those. I can already say I'm chasing on Monday because... It's May!

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