Dendritic Growth Zone and Skew T's

[hm8]

So I'm having trouble fully understanding what the DGZ is and how to read it on a skew t map. I understand that dendrites grow best around -15 C and that this will lead to better snow ratios, but I'm not sure how to see if the DGZ will be "deep" or whatever on a skew t.

Any help?

[OHweather]

From what I understand, and someone can correct me/add to this if I'm wrong, dendrites generally grow between the temperatures of -10C and -20C. Therefor, when one is looking at a skew-t, to determine how deep the dendrite growth zone is you look at what level the atmosphere becomes colder than -10C for the bottom of the DGZ, and look at where the atmosphere becomes colder than -20C for the top of the DGZ.

Take this example from say, Cleveland:

The temperature is projected to fall below -10C at about the 900mb on the above skew-t, and below -20C at just above the 700mb level. I highlighted the -10C line with a bold yellow line, the -20C line with a bold red line, and the blue circle represents the DGZ on the above skew-t. That would make the dendrite growth zone about 200mb thick, which is deep. From what I have observed, anything deeper than 100mb is considered deep, but someone can correct me on that if I'm wrong.

Now, ratios depend on a bunch of other issues. For instance, you can have a 300mb deep DGZ but no moisture within that zone...that would mean dendrites would most likely not form in that column of air. Lift into the dendrite growth zone is also important to good snow growth, although I'm not great at reading the amount of lift present on a skew-t. Not having lift or moisture reach the snow growth zone can cause freezing drizzle to be the precip type even if the entire column is below freezing. Of course, you can have a deep dendrite growth zone but average or even below average ratios if the boundary layer is near or above freezing, causing the snow to start melting and become "wet".

[hm8]

Awesome, makes sense. Thanks!