HID issues with tropical rain

[tjlang]

@bdolan44 and @pfhein - I was noticing during the notebook development that there is a gap in the tropical rain logic in heavy echo. For example, compare the tropical results here:

To the original C-band blended code here:

Some results are missing and the R is being set to 0 (I changed this from your original -9999 values in #42), but echo is still significant.

This appears to be caused by an over-abundance of identified hail at low levels:

Just wanted to bring this to your attention. We may need to look at the tropical C-band HID.

[bdolan44]

I'm aware of this overabundance of hail at C-band. For now, I can add a catch in the tropical rain logic that tries to use R-Kdp if hail is identified.