Reset displayed year rainTotal at year end in Belchertown graph?

[pannetron]

Excuse the pictures if they're frowned upon.  The first shows current yearly rain total graph that does NOT reset at year end.  The second shows, in red, how I would like the rain total line to behave.  How can I do that in the Belchertown skin?  I want to keep the graph displaying 12 months, just want that rainTotal to reset at year end.

Thanks!