I've been getting mysterious appearances of ZL-- showing up during
complicated weather lately and I finally pinned down the problem. When
I use the "Assign" feature in the Precip types step, I set
ZL, L, S to dominant (based on T) in order to get a light wintry mix
in my grids. When I do this, it assigns ZL to areas where my pops are
less than 15 percent. It does not do this for Snow, so therefore this
looks like a bug.
On another note, I notice that when I select ZL as a precip type to
initiate, the GUI has an option to not populate ZL-- for pops less
than 15 percent and this function works as designed (I usually tell it
to do L/ZL in lieu of R). Speaking of that GUI, can we please have an
option to use PoP as a delimiter for choosing L/ZL (instead of QPF)?
The QPF delimiter is not very useful since we have 6-hr QPF grids.