(Not a) Dryline along the KS-OK Border on the Afternoon of 8/3/2023

[gdlewen]

Introduction. I started watching this situation a couple of days ago, and it has developed along lines that pushed away from "possible dryline" to the (less-interesting) "stationary front". I am hoping for some discussion of the general ideas presented here; especially if you know of odd dry line orientations, etc.

Anyway.... There is a strong moisture discontinuity along the KS-OK border in tomorrow afternoon's models that I have convinced myself is not a dry line. I would love to be proven wrong.

WPC forecast analysis shows it as it as a stationary front (no figure given), but when you look at the spatial distribution of moisture along the KS-OK border, it's hard not to think "dry line". I am using specific humidity because it is one of the few quantities that are conservative and can be used as an air mass tracer.



It's even harder not to think "dry line" looking at a S-N cross-section across the KS-OK border:



One more bit of information, though, seems to debunk the "dryline theory": the potential temperature distribution superimposed on a cross section of the Petterssen Frontogenesis (PFG) function depicted below. (I am using the 2D method for PFG applied to each layer, and fully realize that, in this application, the PFG is most-properly calculated using a 3D formulation.) However, using "Layer-wise 2D PFG" in cross-sections seems to be a familiar "cheat" in the literature. Plus I'm just looking for some idea if there is a frontal surface aloft, sloping S-to-N across the moisture discontinuity. It sure looks like it.



So: Stationary Front? or Dryline? Again--if any of you have experience with oddball dry line orientations I'd love to get some feedback...plus dates, of course. (I have other graphics; for instance, moisture convergence etc. But, "Enough is enough.")

 

[Randy Jennings]

I think you are over thinking this. Here are the temps from the 20230803 14z RAP run valid at 21z:



101 in Wichita and 86 in Salina just screams front. If you add in the wind barbs and look at the wind direction changes it screams front even more.

 

[gdlewen]

I think you are over thinking this....101 in Wichita and 86 in Salina just screams front. If you add in the wind barbs and look at the wind direction changes it screams front even more.

Thanks, @Randy Jennings. I was definitely overthinking it--although "overanalyzing" might be a more apt description. (It's also more fun for the analyst.) As far as the temperature gradients, I must confess I dismissed them as too large to be believable: about 36˚C/100km over the width of the frontal boundary. But the point, I realize, is that even though the model gradients were unlikely to be realized, the model was still telling me "front" and not "dryline".

As it turned out, the actual temperature gradients (8/4 00Z) were high, but not the much higher than some strong drylines. (4/23/2021 comes to mind, when I sat E of the dryline in Altus under low ceilings and drizzle and wishing I had brought along a sweater; later that day ∆T’s across the dryline were 10-15+ ˚F).

Anyway—this discussion really did not develop as I imagined…probably because the question was poorly-phrased. It wasn’t a question of “dry line” vs. “stationary front”, but rather what characteristics this "dry front" shared with drylines.