Tricky forecast... First of all, in regards to storm motion, the 0z NAM supports
Bunkers storm motion of a reasonable 30-40kts north of I40, and closer to 25-30kts up along the OK/KS border. Looking at the forecast soundings, it appears as though ELs may be relatively low (~30kft), which means that the 500mb flow may not have as much of an influence on storm motion as usual since less of the storm is 'above' 500mb. I don't think Bunkers' motion takes the buoyancy depth into consideration, which may make it a little less reliable in "low-topped" supercell situations. Regardless, the very respectable 500mb flow is progged to result in
strong deep-layer shear of 60-70kts near I40, increasing to 65-75kts across northern Oklahoma. The orientation of the shear vector (being nearly normal to the pacific cold front) would support discrete convective mode, but the intensity of low-level convergence along the front and intense forcing aloft from DPVA ahead of the impressive vort max may very well (and should very well) eventually yield a squall line.
The run-to-run and model-to-model consistency of the forecast valid tomorrow has been anything but desireable, particularly for those of us basing out of central OK, which is on the upstream edge of the threat area. I haven't been terribly impressed with the NAM-WRF this year, but my hopes are on it verifying relative to the GFS solution, which has persistently been forecasting a faster (and farther east) surface low and threat area for tomorrow (today now, I suppose). Of course, what I "want" has no bearing on what mother nature gives us, so... A survey of afternoon AFDs hints at the limited forecast confidence tomorrow, with a read of the HPC Model Diag. discussion lending support to the GFS (faster) solution and some NWSFOs disregarding the GFS solution while supporting other models (such as the UKMET and ECMWF). So far this year, I seem to remember the NAM-WRF forecasting amplifying troughs to dig too much, thus created over-amplified troughs that move too slowly. However, dprog/dt over the past day or two certainly supports a slower / more westward solution, which helps lend some credence to the NAM solution.
My initial interest for tomorrow was in northcentral Texas east of I35 (just south of the OK/TX border). However, I've been burned several times in the past couple of years in situations such as this (particularly last year, when I was in northcentral TX several times hoping for warm-sector activity in marginal moisture while others were scoring farther north and northwest). I'm now more firmly targeting northern Oklahoma, east of the surface low and near the warm front that the NAM progs to be near an Enid to Tulsa line by tomorrow afternoon. I'm a little nervous about widespread cloudcover and precip limiting destabilization along the warm front, creating a strong instability gradient which may result in storms developing east of the sfc low and moving ENE over the warm front into the stable airmass over extreme N OK and S KS. Convergence along the front in central OK and N TX looks to be pretty strong (per an examination of 850mb UVV forecasts), which may be enough for initiation by afternoon despite the strongest forcing aloft not 'catching up' to the front until after 0z. The NAM disgrees with this in that it does not have appreciable QPF in the warm sector before 0z; the GFS does indicate QPF in eastern OK by 0z, but a little far east for my chase taste. The 0z GFS is also a little more diffuse with the warm front across northern OK.
I'm concerned about the depth of the moisture tomorrow in Oklahoma owing to veered flow just off the surface. This flow profile is also yielding relatively straightline hodographs, though the 0z NAM is showing this less than previous NAM runs. The best curvature is, not surprisingly, farther to the north, nearer the front. For example, the PNC sounding valid at 0z tomorrow evening indicates >350m2/s2 0-1km SRH (indicative of the strong near-surface hodograph curvature). That said, the sounding is also very stable for a surface-based parcel. We've been battling poor moisture (depth and magnitude) for what seems like the entire year, and we've seen the consequences of relatively shallow moisture, which tends to mix out, particularly on days with strong mechanical and convective mixing. Speaking of instability, CAPE isn't impressive either, largely owing to weak lapse rates aloft (not much better than moist adiabatic).
Current target: Between Enid and Red Rock for initiation. I'd much rather chase 150mi to the west, where the terrain is more friendly to chasing, but that just doesn't happen it seems. Road options turn to garbage as one nears Tulsa, so I'm hoping I get lucky in this regard.
!!), so I won't be heading out unless a miracle happens. Good luck and happy hunting to all!!!!!
