Yahweh continues speaking to the people of Jerusalem.
Yahweh speaks of himself by name to express the certainty of what he is declaring. Translate as in Isaiah 30:1. AT: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: rc://en/ta/man/translate/figs-123person)
Yahweh speaks of the things that he does and how he thinks as being far superior to or higher than what people do and think, just like the sky is much higher than the earth. (See: rc://en/ta/man/translate/figs-metaphor)