Too much shear?

[Marshall Stoner]

Great post and I agree with it except for this part. I don't necessarily think you need forcing on the mesoscale, at least, on the meso-alpha or meso-beta scale. Forcing on the meso-gamma, maybe. I was told years ago that a good relationship between maximum updraft height and width is that the maximum potential height is approximately 1.5 times the width of the updraft, which is consistent with your statement. Applying that rule literally, if you can get an updraft around 5 km in diameter, you can generally get it about to the tropopause. I would argue that's more of a storm-scale feature rather than mesoscale.

Thank you! I guess I use the term "mesoscale" somewhat colloquially which is technically incorrect. My real question is what impact vertical shear has on this ratio. I'm also interested less in the height achieved than the ability to organize into a supercell. Of course that adds a lot more variables (like low-level helicity) and it becomes more difficult to account for all the quantitative parameters needed to derive a rule of thumb.

An updraft can easily reach the tropopause and still fail to organize into a supercell. Accounts from chasers demonstrate this. With extreme shear lots of towers will shoot up only to produce a spattering of rain drops and a long thin orphan anvil. Supercell initiation usually happens when you get a fatter more powerful burst that overshoots the tropopause. In some cases that never happens for whatever reason. It could be lack of instability, but I think it can also be lack of something else, like an extra push. There are situations where high shear and lower instability still produce tornadic supercells - particularly winter outbreaks. Something makes it possible some times and not others.

I don't have familiarity with the research literature on the subject. I have a MS degree in atmospheric science but my research was in tropical meteorology, not severe convective storms. I just enjoy theorizing based on my own intuition and experience. I'm smart enough to get away with it a lot of the time. If you have access to papers in this area I'd be interested.