Severe Weather Threat - May 6, 2024

[TH2002]

wxtwitter if the SPC doesn't upgrade to a high risk tomorrow

 

[Fred Gossage]

wxtwitter if the SPC doesn't upgrade to a high risk tomorrow

And they'll do that while yelling "BUST!" at 8:00am for an afternoon/night threat if it is upgraded.

 

[Casuarina Head]

Question for the well-versed: in this kind of thermodynamic setup, with either a) relatively weak or b) meridional large-scale forcing, what is the likelihood that mesoscale models shift overnight decisively toward a significantly larger zone of discrete convection, even south of I-40? Under the circumstances, is the synoptic-scale trend set in stone on the guidance, or is there room for a shift toward stronger forcing and/or foci (i.e., outflow boundaries) across more of the warm sector? Most of the mesoscale models still seem to indicate a strong potential for an isolated discrete cell or two capable of producing a few intense/long-tracked tornadoes, but otherwise still seem to be holding back from a more widespread event. Based on past experience, how drastic a shift overnight—into HIGH-Risk territory—is within the realm of possibility? At any rate I personally expect that at least one cell will manage to produce a very intense tornado or two. Factors other than height falls and/or capping clearly favour an extremely high ceiling.

 

[Fred Gossage]

The large scale ascent / height falls / etc., is mostly set, but a trend toward slightly weaker capping, a few prefrontal confluence bands or horizontal convective rolls in the warm sector, and/or stronger low-level convergence in the dryline circulation would all lead to a scenario with a higher chance of sustained convective initiation in the Oklahoma threat area. Even as it stands, taking an overall blend of the HRRR/WRF-ARW/WRF-NSSL/MPAS/Baron3k solutions, we're likely only 1-2 modeled sustained supercells away from them likely being in a situation where they'd have little hesitation on placing a High Risk, at least based on history of events in the past.

 

[TornadoFan]

wxtwitter if the SPC doesn't upgrade to a high risk tomorrow

B...but wxtwitter knows best!!!1 *sarcasm*

 

[jiharris0220]

If all models across the board sustain the same consistency with the parameter space into tomorrow there will be little reason to abstain from issuing a high risk.

Rarely do you see high value UH tracks spread across such a large area. I haven’t seen this since March 31, 2023.

 

[Fred Gossage]

If all models across the board sustain the same consistency with the parameter space into tomorrow there will be little reason to abstain from issuing a high risk.

Rarely do you see high value UH tracks spread across such a large area. I haven’t seen this since March 31, 2023.
View attachment 26326

Only about this much of it is tied to a higher potential for mostly discrete, long-tracked storms capable of producing higher-end tornadoes. Most of the rest of that is mixed/mode messy, and I would imagine some of the northern/northeastern side of that may not even be fully surface-based. Updraft helicity doesn't discriminate on surface-based vs elevated environments.

 

[jiharris0220]

View attachment 26327
Only about this much of it is tied to a higher potential for mostly discrete, long-tracked storms capable of producing higher-end tornadoes. Most of the rest of that is mixed/mode messy, and I would imagine some of the northern/northeastern side of that may not even be fully surface-based. Updraft helicity doesn't discriminate on surface-based vs elevated environments.

Yeah, most of the northern stuff is probably hail, (which also can produce UH tracks). But I definitely wouldn’t sleep on southern Nebraska, could pull a surprise or two.

 

[warneagle]

B...but wxtwitter knows best!!!1 *sarcasm*

 

[jiharris0220]

Here’s a favorite I use as gospel.

 

[Casuarina Head]

The large scale ascent / height falls / etc., is mostly set, but a trend toward slightly weaker capping, a few prefrontal confluence bands or horizontal convective rolls in the warm sector, and/or stronger low-level convergence in the dryline circulation would all lead to a scenario with a higher chance of sustained convective initiation in the Oklahoma threat area. Even as it stands, taking an overall blend of the HRRR/WRF-ARW/WRF-NSSL/MPAS/Baron3k solutions, we're likely only 1-2 modeled sustained supercells away from them likely being in a situation where they'd have little hesitation on placing a High Risk, at least based on history of events in the past.

Re: the prospects of a HIGH Risk tomorrow: I think a cause of misunderstanding is the fact that I prefer the SPC’s original methodology for verification of outlooks, which seems more objective than a strictly probabilistic approach. Also, the criteria for a HIGH Risk etc. were unclear to me, for the online resources that I resorted to, taken together as a whole based on wording, seemingly indicated that a HIGH TOR-wise would feature more than a couple of E/F3+ tornadoes, be more widespread, and feature at least one E/F4+, along with numerous discrete, long-lived supercells. So I was going by the SPC’s own Web page and related sources, interpreting description(s). I utilised this as my guide in the past as well, which has influenced debates on climatology etc. Almost certainly I erred (you are far more intimate with the history than I am), but I do not think it is completely useless. Now this is coming to fore again, in regard to the likelihood—and threshold—of a HIGH Risk tomorrow.

To me a HIGH Risk TOR-wise is synoptically evident and juxtaposed with the best thermodynamics over a wide area, with mesoscale factors playing less of a role in setting overall expectations rather than modulating individual storms’ characteristics. At the moment tomorrow just does not quite meet the cut, based not only on current mesoscale trends, but also on synoptic-scale verification. Right now the best dynamics are expected to act in a rather more limited fashion with the best thermodynamics than is expected for a HIGH Risk, and there are potential issues with EML-related, diurnal capping and weak forcing over the southern extent of the hatched area (along and south of I-40), while (quasi-)linear forcing comes quite close to the big supercell or two in the northern extremity of OK. Past Plains outbreaks in this area with three or more (long-lived) EF3+, one or more EF4+, and widespread discrete supercells tended to be more evident synoptically in advance, so that the mesoscale features would act more as accoutrements of an already-conducive, set environment. Right now I think a full-spectrum MDT is most appropriate for tomorrow.

 

[andyhb]

Re: the prospects of a HIGH Risk tomorrow: I think a cause of misunderstanding is the fact that I prefer the SPC’s original methodology for verification of outlooks, which seems more objective than a strictly probabilistic approach. Also, the criteria for a HIGH Risk etc. were unclear to me, for the online resources that I resorted to, taken together as a whole based on wording, seemingly indicated that a HIGH TOR-wise would feature more than a couple of E/F3+ tornadoes, be more widespread, and feature at least one E/F4+, along with numerous discrete, long-lived supercells. So I was going by the SPC’s own Web page and related sources, interpreting description(s). I utilised this as my guide in the past as well, which has influenced debates on climatology etc. Almost certainly I erred (you are far more intimate with the history than I am), but I do not think it is completely useless. Now this is coming to fore again, in regard to the likelihood—and threshold—of a HIGH Risk tomorrow.

To me a HIGH Risk TOR-wise is synoptically evident and juxtaposed with the best thermodynamics over a wide area, with mesoscale factors playing less of a role in setting overall expectations rather than modulating individual storms’ characteristics. At the moment tomorrow just does not quite meet the cut, based not only on current mesoscale trends, but also on synoptic-scale verification. Right now the best dynamics are expected to act in a rather more limited fashion with the best thermodynamics than is expected for a HIGH Risk, and there are potential issues with EML-related, diurnal capping and weak forcing over the southern extent of the hatched area (along and south of I-40), while (quasi-)linear forcing comes quite close to the big supercell or two in the northern extremity of OK. Past Plains outbreaks in this area with three or more (long-lived) EF3+, one or more EF4+, and widespread discrete supercells tended to be more evident synoptically in advance, so that the mesoscale features would act more as accoutrements of an already-conducive, set environment. Right now I think a full-spectrum MDT is most appropriate for tomorrow.

Without going into this too much, "quasi-linear" forcing can still yield plenty of supercells (e.g. that 18z HRRR run). The key thing in KS with tomorrow will be if things go upscale quickly around initiation due to slightly less favorable hodographs/drier conditions near the dryline early on, which could result in a lot of cell mergers/left splits/outflow complicating convective evolution. I do not see at all how tomorrow is not "synoptically" evident. We would not be dealing with a large warm sector filled with moderate to high end instability/shear combinations if that was not the case.

 

[jiharris0220]

Here’s a post that paints the picture quite nicely.

 

[wolfywise]

Oh my god the RAP. That is scary change from the 15z.


15z for comparison.

 

[Shakespeare 2016]

Here’s a post that paints the picture quite nicely.

The v word.

 

[Shakespeare 2016]

Here’s a favorite I use as gospel.
View attachment 26329

I love that.

 

[Todd]

Here's what the NWS Norman, OK stated regarding any upgrade to High Risk for Monday.

 

[Shakespeare 2016]

Here's what the NWS Norman, OK stated regarding any upgrade to High Risk for Monday.

There have been numerous times where Moderate Risk's have done better than High Risk's.

 

[JPWX]

Here's what the NWS Norman, OK stated regarding any upgrade to High Risk for Monday.

I wonder if Rick Smith wrote that tweet since he works at Norman

 

[Brice W]

Here's what the NWS Norman, OK stated regarding any upgrade to High Risk for Monday.

They’re right, it shouldn’t matter. Cause at the end of the day we need people to be prepared for warning systems ahead of something, not the pretty PINK colors you see on a severe weather outlook. Lives are more important than whether an event is a HIGH or MDT risk.