I expressed my pessimism about this weeked in the long-term thread in W&C, and that sentiment hasn't changed much. Shear profiles from far northern OK into southern KS don't look too bad, with rather loopy low-level hodographs. My main concern still involves available moisture. 12z soundings from southern/eastern TX indicate that the moisture is extremely shallow, which can be expected when we deal more with modified cP air than true tropical air. For example --
BRO shows moisture about 50mb deep, decreasing to about 20-25mb deep at
CRP;
LCH indicates about 40-50mb deep moisture as well, with
FWDjust pitiful. With a moderate LLJ tomorrow and strong insolation / diabatic heating, I'm extremely worried that the moisture that we may have may completely mix out. Models continue to handle the surface moisture fields extremely poorly as well... For example, the 12z 8km Central US WRF run indicates >65F Tds across all of eastern KS east of I35 right now (9hr forecast). Surface observations, however, show that the Tds in that area are largely in the 52-60F range. This is a little surprising, since the WRF, from my experience, tends to be much better (relative to other op models) with the handling of surface dewpoints. In addition, the same models indicate >50F Tds in northern KS right now, whereas surface obs indicate Tds are in the 30s. Ugh!
Now, moisture may mix out some tomorrow, but mixing also works to make the low-level thermal profile more homogenous (i.e. nearly dry-adiabatic low-level lapse rate), which can help mix out some cap / negative area. However, looking at, for example, the NAM forecast sounding for 21z tomorrow at PNC, if we adjust the surface dewpoint to 59-60F, the LCL becomes ~3000m (about 725mb), with CAPE about cut in half and CINH double (at least) the NAM forecast. This is quite worrisome. Again, the shear profiles look sufficient for supercells (heck, check out the WLD sounding from the 12z NAM -- awesome hodograph curvature, with 430 0-3km SRH and 45kts 0-6km shear), but marginal moisture may inhibit thunderstorm development all together (the WLD sounding valid 21z indicates -60 j/kg CINH without any adjustment to the moisture profile). If we do mix deeply tomorrow, we could get some very high-based supercells.
All this said, I may head up towards the OK/KS border. If we can get a thunderstorm or two, I think there is a good chance for a supercell given moderate CAPE and deep-layer shear. The hodograph curvature also looks pretty good, which will help enhance updraft strength as we get favorable vertical perturbation pressure gradients. Low-level shear looks pretty good from the northern tier of OK counties into southern KS, but tornado potential looks minimal given very high LCLs and tendency for strong sub-cloud evaporational cooling.
EDIT: I see
this afternoon's OUN AFD indicates this line of thinking as well:
<div class='quotetop'>QUOTE("OUN AFD")</div>
SEVERAL MODEL RUNS...MOST NOTABLY THE PARALLEL NAM...HAVE DEVELOPED
CONVECTION ALONG THE FRONT IN NORTHERN OKLAHOMA SATURDAY EVENING AND
OVERNIGHT. THIS MODEL...ALONG WITH THE NAM-ETA AND GFS...ARE ALL
STRONGLY OVERESTIMATING THE DEPTH AND MAGNITUDE OF BOUNDARY LAYER
MOISTURE. PARALLEL NAM MAY BE THE CLOSEST TO REALITY...EXCEPT FOR
EXCESSIVE MOISTURE POOLED ALONG THE FRONT. USING MORE REALISTIC
DEWPOINTS IN THE NAM-ETA SOUNDINGS YIELDS LITTLE IF ANY INSTABILITY
SATURDAY...SO FORECAST WILL REMAIN DRY.
EVEN THE AIRMASS OVER THE GULF OF MEXICO IS RELATIVELY DRY...WITH
DEWPOINTS AS LOW AS MIDDLE 50S IN THE CENTRAL GULF. TROPICAL
MOISTURE IS CONFINED TO THE CARRIBEAN AND NEAR THE YUCATAN.[/b]
