Paul Schmit
EF0
Thank you very much, Tim, for such a thoughtful response, it reads in such a wonderfully technical way that I'm tempted to ask for citations from the literature! I recall encountering these concepts regarding LM/RM motion relative to surface boundaries in Bluestein's 2007 review article, though the original work was apparently Bluestein and Weisman (2000). Do you have a preferred reference spelling out the protocol for extracting the LM/RM vectors from radiosonde data? I can see how excessive linear convergence along a boundary could compromise isolated updrafts from taking root early on in initiation. As for the thermal gradient comment you make, is this because a strong thermal gradient across a boundary at the surface indicates the thermal wind vector (i.e. low-level wind shear vector) is most likely oriented parallel to the boundary, implying that LM modes will tend to propagate into stable air while RM mode will tend to congeal into a line? Just making sure I've got the right physical mechanism in mind.
As for progressive vs. serial lines, it definitely seems that a bunch of congealing discrete RM modes with loads of downstream CAPE and SRH (shear vector mostly parallel to boundary) would interact far more cooperatively/coherently than a bunch of colliding LM/RM modes (shear vector mostly normal to the boundary), all other environmental variables being equal. So your discussion of serial/progressive systems seems to make good sense.
I did encounter some amazing stratiform lightning in west OK the night of 5/18 this year, and you're right, the CC lightning seemed to go from horizon to horizon, plus tons of beautiful CG, with only modest rain obscuring the view.
As for progressive vs. serial lines, it definitely seems that a bunch of congealing discrete RM modes with loads of downstream CAPE and SRH (shear vector mostly parallel to boundary) would interact far more cooperatively/coherently than a bunch of colliding LM/RM modes (shear vector mostly normal to the boundary), all other environmental variables being equal. So your discussion of serial/progressive systems seems to make good sense.
I did encounter some amazing stratiform lightning in west OK the night of 5/18 this year, and you're right, the CC lightning seemed to go from horizon to horizon, plus tons of beautiful CG, with only modest rain obscuring the view.
