This poem jumped out at me because of the way O' Brien uses sensory images to create a tangible experience of time passing. He describes fall / October "dropping down" into the world as a "bland return" to the previously flourishing summer landscapes. Paired together with more traditional, natural imagery of "used leaves" and "banks of clouds" the reader is left with a deeply unsettling image of how seasons changing can breed isolation as the year "takes itself apart".
I think your term "isolation" is an interesting one to describe how the image has one foot in the "inner realm." I wonder what other words we could use to describe it. What's with "heat around me" and no friends I WANTED. It's like isolation--but a special kind of isolation.