Even if clouds are to be the center of the interest in a painting, the viewer's eye must move around the entire frame, not just stop at the clouds. Here's how I accomplished this using a balanced composition and lines.
The textured surface in the cloud highlights helps create interest in the lightest portions of this image. The tiny shadows created by the raised areas of the highlights help create interest. The layering of color in the highlights makes those tiny shadows have different colors too. As the paint under the top layer (Pastel in this case but in oil painting too) peaks through the highlighted areas have more interest in a smaller space.
The darker areas of the clouds have violets in them. Not just any violet, but gray-violet. The grayed violet make the color weaker and go back while the brightest parts of the clouds come forward because they have the light yellow colors over the textured highlights. Yellow and violet are complementary and when placed beside one another, they vibrate. But because the violet is not pure value or saturated, but grayed, the space the two colors occupies is different, making one come forward and other go back. As the highlight on the horizon comes forward, the color shifts from a muted yellow green to one that is purer or more saturated, again, the color is moving the eye forward and back into the space. In this case, the eye is moving up to the clouds, the intended center of interest.
Sharp Edges VS Soft Edges
The other factor in making the clouds the center of interest is the use of sharp and soft edges. The highlights are sharp edges, as sharp as is possible with that much texture. The edges of the trees, the various shades and values of green in the foreground all are just lumps and suggested shapes. By controlling the edge sharpness I was able to control the center of interest more than if I had made everything blurry. If I made sharp edges on everything, then that would detract from the clouds and dilute my intended center of interest.
The above notan pen and ink with pencil sketches show how I played with design and line to move the eye. Note how the trees on the right are bending in a breeze and the trunks are not strait. This helps move the eye back into the piece and back toward the highlight of the clouds. The small clump of trees to the left have a darker patch that trails off to the right to move the eye up the trunks and around back to the right set of trees and back around -- there's a circular pattern going on in this design choice
What I learned
I had to bring the highlight down and slightly out of the frame to give a way to enter the piece. Blocking off this entry point might have blocked access if a viewer isn't coming to the piece from left to right. I think this is debatable. This is maybe more appropriately "what I still need to learn." There's a debate I still have about this. I've done so many pieces with the bottom blocked off in solid darks and criticism is that there is no way to enter the work. But history of art shows many paintings with dark bottoms and the circular motion of the design is enough. Hmmmm.