Mast on second level and grounding question

I'm not easily able to run a ground wire from the location of my mast to the grounding rod where the electric power comes to the house (second level of 1.5 story house - there is only a single room at this level and the walls don't extend out to the border of the home). So I will have to run the mast grounding wire a bit along the shingles to a new grounding rod. I will also ground the Lightening arrester to the same wire and rod.

Am I at extreme risk by not having that second grounding rod connected to the one that is by the electrical box?

I'm using #8 solid copper (bare) for the grounding wire, and want to reduce the path from the mast to the new rod to be as direct as possible.

Just in case I wasn't clear, I will try to attach http://ift.tt/1ilfPgI a photo of the area