...the confluence band moving north from the sharper dryline gradient in N TX. As this band nears I-35 at/north of OKC, we could see more robust CI. This is a fascinating example of the dryline as less of a "line" and more as a broad zone. (2/2)
2200z: The many CI attempts along I-44 have struggled, while those closer to I-35 are far more numerous and organized. While the dryline is technically in W OK, there's a broad zone of decreasing Td as far east of I-35, likely contributing to the struggles of sustaining CI along... (1/2)
...on CI in C OK/N TX and the early evolution of convection and its hazards. (5/5)
Notably, this distinct secondary Td gradient in OK is not developed yet in the current obs (although the current Td gradient from C to W OK is consistent with latest modeled evolution). When and where these localized enhanced confluence zones set up will likely have a significant influence... (4/5)
...with the lee cyclone? Either way, as modeled, this zone in C OK and the tightest Td gradient in N TX appear to have the strongest surface confluence. I would expect these zones to be the most likely areas for successful CI, with other dryline-CI attempts struggling with weaker forcing. (3/n)
Latest HRRR depicts 00z dryline across W OK. But, somewhat similar to yesterday, there is a notable secondary ~10F Td gradient in C OK ahead of the dryline. Maybe this is due to differential heating related to current cloud cover lingering in C OK? Or confluence band associated... (2/n)
More #okwx #txwx dryline yapping from me: Latest HRRR runs have reduced the CIN in central OK, possibly in response to assimilating 18z Norman sounding showcasing just a smidge of a warm nose remaining. As such, latest runs have also begun depicting dryline-vicinity CI ~22z in N TX. (1/n)
...of synoptic-scale and dryline lifting.
3) The other wild card here is the evolution of the lee cyclone. Any change in propagation speed or intensity relative to modeled will have a ripple effect on these smaller-scale factors directly influencing CI.
Another difficult CI forecasting day. (9/9)
...may not have as substantial as a role as it did yesterday.
2) How does the leading upper-level vorticity maxima evolve? Faster eastward propagation can make dryline CI more likely as upper-level descent more quickly moves east of C OK. Slower propagation may allow for a positive phasing... (8/9)
In "synoptically-active" dryline cases such as this, there are far more knobs to turn to make dryline CI less/more likely. A few things to watch for:
1: How does current cloud cover evolve and influence dryline propagation relative to modeled? Given the other synoptic forces at play, this... (7/9)
This is starting to get out of my depth, but a weak vorticity maxima appears to cross C/E OK ~18z. This may serve as the forcing for E OK convection seen in the HRRR, but in the wake of that, descent would be expected across C OK, which may be somewhat suppressing dryline lifting processes. (6/9)
(it's not just the HRRR either. Other CAMs also only depict convection well east of the dryline) (5/9)
Forecast sounding from Norman at this time shows a decently stout capping inversion still present as the likely culprit, with notable CIN present across much of central OK and N TX. (4/9)
The HRRR depicts a sharp dryline extending south from a lee cyclone in NW OK. Yet, aside from a couple of storms in N TX, the HRRR isn't depicting much CI along this dryline, which seems odd at first glance. (3/9)
Currently, the dryline is in the central TX panhandle, with a cold front trailing behind it and intersecting it in the north. While central OK is currently under heavy cloud cover and some precip, this is quickly moving east, setting up the potential for a lot of sun ahead of the dryline. (2/9)
3/6/26: Another potentially big severe day with a lot of moving pieces. Similar to yesterday, I'm going to take a dive into just the dryline forecast and see what it might mean for dryline CI in C OK and N TX (1/9) #okwx #txwx
The dryline is well west of the action, so how CI evolves over the next few hours is outside my knowledge realm. On a side note, it's pretty cool to see the difference in color between the west and east side of the dryline, with the east (less well-mixed) side appearing murkier! (3/3)
With <1 hr of daylight left, time to see if there's enough focused convergence (perhaps aided by the Caprock) to get sustained CI, and if there's been enough destabilization across the E TX panhandle and W OK (which has been under high cloud cover all day) to realize the severe potential. (2/3)
0000 UTC: There's been robust cumulus development both east (south-central TX) and west (along/east of I-27) of the thickest portion of the high cloud train. I wonder how much differential heating between the more/less high cloudy areas may be contributing to some of these convergence zones (1/3)
tl;dr: a potential failure mode for today (3/5) is current cloud cover and how that may "slow down" BL mixing compared to modeled. For tomorrow (3/6), I am still concerned for central OK severe potential despite many CAMs wanting to push the dryline through and have CI farther east. (15/15)
The HRRR is not the only CAM with this type of evolution for tomorrow, so it will be interesting to see how that evolves over the next day. (14/n)
...the HRRR may be too aggressive mixing the dryline that far east by 00z tomorrow. Interestingly, the HRRR also doesn't produce any CI until after 00z and in far eastern OK, which could be because of a "too fast" dryline evolution and how that phases with other fronts/synoptic factors? (13/n)
That was longer than I thought so I'll be brief about tomorrow (3/6). Stronger synoptic forcing will result in a more "synoptically-active" dryline, where advection and other processes in addition to BL mixing influence dryline evolution. Similar to today, I suspect... (12/n)
SW TX may be another spot to watch for CI today. Clearer skies may allow for more typical diurnal dryline/BL evolution, but mediocre BL moisture and weaker kinematics may be limiting factors for storm intensity/longevity. (11/n)
There may be other factors I'm less well-versed in influencing the Td evolution (strength of lee cyclogenesis, etc.), so take this with a grain of salt. But for me, I will be closely watching cloud cover, obs Td, and modeled Td trends for my own short-term CI forecasting. (10/n)
...would suggest to me that the model may be adjusting to obs that the mixing isn't occurring as quickly as previous runs suggested. This can shift CI west, make it later (if terrain effects are needed for CI), or prevent CI altogether if the BL east of the dryline never mixes substantially. (9/n)
I'm not a modeling expert, but in my experience I've generally found the HRRR to be too aggressive with its diurnal BL mixing. Is that happening today? Model trend loop shows the sharpest Td gradient in northern TX panhandle shifting west, with increasing Td east of the gradient, which...(8/n)
CI appears to be relying on strong BL mixing extending east into this favorable terrain and favorable moisture of east TX panhandle/west OK. One failure mode I'm concerned about is the cloud cover (incl. high clouds) slowing the diurnal BL mixing process and preventing the cap from mixing out. (7/n)
So what does this mean for CI? The HRRR is far from the only CAM depicting CI this evening in the TX panhandle. The strongest CI (and where SPC highlights the greatest risk) is in the vicinity of the Palo Duro Canyon, so there may be some favorable terrain effects. (6/n)
Satellite at 1715z depicts much of the TX panhandle socked in with low clouds, as well as a layer of high clouds over top. So I tend to believe the solution that this cloud layer will persist through the day, with the strong synoptic forcing not entering the area until tomorrow. (5/n)
