My dilemma in deciding how to score this it that the subject of interest is the storm, i.e. most of the image, and those stormy skies also constitute the negative space. So the negative space does not add to subject, it "is" the subject. On further reflection I'll consider the band of crepuscular rays (which I like) as the subject.
A great sense of space and light here, but I so wish we had one building, or figure, or even a humble cow to act as the focus for all this empty. I find my self thinking "Is the sky offsetting the land? The trees? What?" Still it is a beautiful image, it only lacks that one element to be in ribbon land.