Ok I don't know why the pic is sideways, but check this out on the side of my neighbor garage. We have three that we have found so far this year around the house. Hopefully this isn't bad news for the upcoming winter but that's what I have heard.
It's been several years now but mowed all year long under a pine tree in the yard, finally about the first week of September my neighbor was over and said wow that's a huge hornet nest. I said where??? It was hanging from the lowest branch, when I would pass under it my head couldn't have been...
I have two hornets nests above my houste this year in the same tree. Fortunately I do not have a war with them and the yellow jackets going on. Good luck with that one. Because of the height it would probably be best to try to locate the yellow jackets and go that route of killing them first...