Pre-Frontal Troughs

[Kyle Brittain]

What is going on in the mid/upper troposphere to induce their development? On the surface, and in severe plains outbreaks, a form of prefrontal trough is often manifest as the dryline, but this isn't the result of anything going on aloft so much as the convergence that occurs along the boundary. But can you have a prefrontal trough that isn't a dryline? For instance, a simple convergence line of say SWly to SEly winds in the warm sector (perhaps induced by the trough). Such a feature must be a surface reflection of something going on aloft in this case? And if so, what clues are there to be able to forecast its development?

I know that they can be favoured zones of CI, and that they can often produce discrete modes due to their angle relative to upper winds, before the cold front comes and sweeps it away (along which there can be some linear MCS).

 

[NealRasmussen]

And you can have pre-frontal sfc troughs in front of drylines.

To my thinking, it's a wrinkle in the boundary layer. Lifting a table cloth from the center of the table causes wrinkles. Somewhat akin to the Wilson and Compton chamber. Periodic stress axis?
https://en.wikipedia.org/wiki/Cloud_chamber#Invention

Of course I can't find the picture now, but the cloud chamber that inspired the physics folks produced a nice star-fish pattern. Outward extending radial lines which cloud would form. I forget if 6 or 8 arms/axis. But it looked familiar storm-wise. More... geometric than this one
http://www.nucleonica.com/wiki/images/thumb/5/5f/Cloud1.png/250px-Cloud1.png

 

[Shane Eagan]

If you're up for reading, this Schultz paper is a pretty good overview of the mechanisms behind pre-frontal troughs along with a review of the relevant literature: http://www.cimms.ou.edu/~schultz/pubs/schultz05.pdf