'To howl' signifies grief caused by vastation.

In Ezekiel 32:18, this signifies grief on account of their damnation. (Apocalypse Explained 659[4])

In Micah 1:8, this signifies the grief of the angels and of the men of the church. (Apocalypse Explained 695[24])

In Matthew 13:42, this signifies the grief of sensuous men in their opposition to truths. (Apocalypse Revealed 435)

In Revelation 18:9, this signifies people in control in the church mourning from embarrassment at the loss of wealth. (Apocalypse Revealed 467)

(References: Apocalypse Explained 406)