Thanks for your input Matt and Jeff. I am certainly an amateur when it comes to forecasting and value having my crude understanding of the atmosphere nudged in the right direction by those actually educated in it.
How about in the dry air on and just west of the dryline? That convection originates in the EML doesn't it? It would root to the surface in the moist air east of the dryline right? In this case the extremely stout capping inversion would keep it elevated wouldn't it? Earlier runs showed some convection firing in the dry Texas panhandle air. I assumed this was occurring with elevated instability in the EML that was more moist than the dry boundary layer. I see some potential near Wichita for supercells and even a tornado or two provided a linear storm mode doesn't dominate. I was under the impression that the convection further south originating over the dry desert air would never become rooted to the surface due to strong capping though.
MODS: I apologize if this doesn't belong in this thread. Move it if appropriate.
I don't think this would happen. The air mass at and west of the dryline would be very warm and deeply mixed. Therefore, it would be almost unheard of to have elevated instability, and any convection that developed in the cT air mass would be surface based. If that convection managed to cross the dryline (which I've never really witnessed myself before but I don't see why it can't happen) there's a good chance the storm would die since it would get choked off by the capping inversion over the mT air mass. However, if the storm was well-established with a wide and very strong updraft, the corresponding surface convergence and momentum of the updraft air below the LFC may be enough to force parcels to overcome their CIN and keep the storm going. However, the storm would still be surface-based then, since, as I described in my previous post, it is highly unlikely that with an EML in place, elevated parcels would be more unstable.
I should probably clarify the statements I made in my previous post. In the mT air east of the dryline, you certainly can have elevated parcels that are part of the capping inversion just below the EML base that possess CAPE. However, those parcels will pretty much always have less CAPE and more CIN than surface based parcels. It seems natural to think that the most likely parcel to reach its LFC and spawn convection will be the most unstable one (most CAPE, least CIN). That favors the surface-based parcel over any elevated parcels in almost every situation, at least during the day. In the evening, convergence at the nose of a LLJ or some sort of low-mid-level frontogenesis may provide an elevated trigger. To illustrate this, I've put together a sample analysis of a typical sounding taken from an mT air mass capped off by an EML from recently:
I've also marked three interesting parcel paths. The mixed-layer parcel representative of PBL/surface conditions is in black. It is the most unstable as it has the most CAPE. The blue one represents the next parcel immediately above the top of the mixed-layer. Granted, I'm doing this entirely visually (not using numerical data, so there may be small errors), but it appears the theta-e of that parcel is slightly lower than that of the parcel coming from the PBL (it is following a cooler moist-adiabat). The very next parcel above that in green obviously has much less CAPE. It's hard to visually compare the amount of CIN between the three parcels since they have different LCLs and LFCs, but it very well seems like the blue parcel just above the top of the mixed layer has a little less CIN than does the mixed-layer parcel. However, if you count the amount of additional resistance to upward motion by buoyant forces in the layer between the origination of each parcel and it's LCL, the CIN difference really shrinks between those parcels. Also note that those parcels are very close to each other vertically, and under strong daytime heating, it's pretty likely that the blue parcel would eventually mix into the PBL and become part of it anyway. You can see how even a slight vertical distance above the blue parcel, the green parcel has far less CAPE and probably just as much, if not more, CIN than the parcels below. You could imagine the parcel path for the parcel immediately above that one and see how quickly the level of instability drops off.
What the above shows is that there really is very little "elevated instability" when an EML overlays an mT air mass. Not to mention, if one of those parcels that is sitting just above the top of the PBL were to activate before a surface-based parcel, once an updraft became established (i.e., with convergence at and below its originating level), there wouldn't be much additional CIN for a mixed-layer (black) or surface-based parcel to have to work through to also activate. Most likely the forcing provided by the established updraft would be sufficient for those lower parcels to activate, and you'd have a surface-based storm in no time even if the very first parcels may have been slightly elevated.
The only cure is next week's mouth-watering setup. This lackluster pattern of late will break, and probably break big.
