Amos 3

1. Israel has disobeyed the LORD and turned away from Him.

2. The LORD set apart the descendants of Abraham to be His people, the only people in all the world that He treated in this way. Yet they turned away from Him.

This is why Israel deserves God's judgment: "Therefore, I will punish you for all your iniquities."

3-6. There is a series of questions here, all with no as an answer. The final question is: "If a calamity occurs in a city has not the LORD done it"

Presumably this refers to the destruction that will come to the cities of Israel. It is God's judgment upon Israel.

Does this apply to what happened to New Orleans from Hurricane Katrina, or to New York on 9/11? Or Hiroshima at the end of WW II? At any rate, it applies to the calamities that Amos foretells in chapters 1 and 2.

7. The LORD has told Amos ahead of time what He will do to these cities and it is customary for God to forewarn the prophets what He plans to do.

8. The forewarning is like the roaring of a lion. Death will come to the cities that the LORD plans go destroy and the prophets will speak out about it.