Comets are non-sentient and have no will for good or evil. There is probably no such thing as "luck".
The real question is how God balances His foreknowledge and creative hand against the free will of each human being in such a manner that disasters work to God's will and to the good of his children even as they bring temporary grief to his own and damnation to those who have rebelled. God, in His wisdom and power, is indeed awesome in the truest sense of the word.
Reading about these world-wide catastrophes, can't help but wonder if they're not recounted biblically in the 7 year famine during Joseph's rise to power in Egypt, and the famine that occurred during the time of Elijah.
the Sumerian story of Flood, on which basis the Genesis Noachian Flood story is built
I get really tired of the claim that the Israelites stole these stories from other cultures. I have a theory about why all these similar stories exist--because the event really happened.
Before writing occurred, history was handed down as oral tradition. So, in the telling of the tale, minor changes would occur over time much like that game where a group of poeple start a saying at one end of a line and by the time it gets to the last person it no longer resembles the original statement.