He said: "Yahweh will roar from Zion, And utter his voice from Jerusalem; And the pastures of the shepherds will mourn, And the top of Carmel will wither."
In  Joel 3:16, Jehovah is represented as roaring on behalf of Israel, but in the stern denunciations of Amos, he is represented as roaring against Israel.  It was calculated to strike terror into the hearts of the wicked and lead them to repentance.