Not only is the "vapor" or "water canopy" (as we JWs called it in the 1980s) not representative of the original reading of the ancient Hebrew view of the universe (demonstrated in the chart I uploaded on my last post on this thread), the whole idea that "it never rained on earth until Noah built the ark" and that "the flood was historical" are further Watchtower nonsense that has no support from Biblical scholars, including the majority of those in so-called Christendom.
The idea that the "expanse" or "firmament" was some envelope of water that was later punctured to create the flood and allow the "waters above the expanse (firmament)" to flood the earth in Noah's day would have meant that all of outer space would have flooded down on earth. We wouldn't be here if that was true.
Remember, according to the chart, the cosmological model of the ancient Hebrews did not include a vacuum of space. The vacuum of space was just an ever-extending sea of water in their eyes. The "heaven" where God lives is above this "outer space" of waters. That is why you often read things in the Scriptures such as:
"The Lord sits enthroned over the floodwaters; the Lord sits enthroned—king forever!"--Psalm 29:10.
Even with the latest revision, the New World Translation is still very stilted and the translators apparently didn't care to make the text read as easily as they could (to likely perpetuate the "vapor canopy" belief). NWT has Genesis 1:6 as "'Let there be an expanse between the waters, and let there be a division between the waters and the waters.' Then God went on to make the expanse and divided the waters beneath the expanse from the waters above the expanse. God called the expanse Heaven." Confusing, no?
The Common English Bible on the other hand renders it: "'Let there be a dome in the middle of the waters to separate the waters from each other.” God made the dome and separated the waters under the dome from the waters above the dome. And it happened in that way. God named the dome Sky."
The dome was meant to allow the space for air and life to exist for earth under the vast cosmos of waters that the ancients believed space was filled with. Most eastern cultures even believed water contained all the elements for life and that life was actually drawn from the great cosmos of seas.
This is why 2 Peter 3:5 states: "Heaven and earth were formed long ago out of water and by means of water. And it was through these that the world of that time was flooded and destroyed."
There is circumstantial evidence that because the ancient Mesopotamian cultures were subject to floods that a common flood legend circulated among them. It appears that each claimed the story as original to their own particular ethnic group, and the Hebrews were no different. Subject to a series of doublets, it is quite evident that the Noah story in the Hebrew text developed from a series of redactions that occurred over time.
But it was after the Babylonian exile that the story appears to have become set as we have it today. While it is unclear if the Hebrew's "Noah" figure was a literal man who survived one of the great Mesopotamian floods with his family and a few farm animals (and scholars believe the original story, whichever culture it actually came from, is as simple as that), the Babylonians had a twist that was borrowed and altered the Jewish tale the most.
The official Roman Catholic Bible in the U.S., the NABRE, states the following in a footnote in Genesis 6 about the flood: "The biblical story ultimately draws upon an ancient Mesopotamian tradition of a great flood, preserved in the Sumerian flood story, the eleventh tablet of the Gilgamesh Epic, and (embedded in a longer creation story) the Atrahasis Epic."
The scholarly view is that the Jews recognized the Babylonian tale as their own "Noah" story, and once Babylon fell and they returned to their land, the Jews incorporated the Babylonian details to poke fun at the now defunct Babylonian gods (who were viewed as defeated with the Jewish return to the Fertile Crescent). The details that atheists (and yes, many believing theists too) often point out are impossible to justify (the building of the ark, its size, the idea that two of each animal were saved within, etc.) are the details from the heathen tales added by the Jews to their own after the return from Babylon.
Why would they do this? The theory goes that the idea that the Babylonians would worship gods responsible for destroying the earth by flood (why worship a god who will kill you at whim?) was ridiculous to the Jews. These points got woven into the story to include not only some universality but as a response to these ideas, and with a different ending to make a religious point. In the Jewish story (unlike the others) their God is "sorry" or "regrets" the idea of flooding the world. God promises never to do it again, and even gives the sign of his "bow" hung up in the heavens (showing he will never strike humanity with "arrows") as a promise. Noah and his family, representative of all humanity now, then give God worship in response. The flood story is no longer so much a story of a literal flood therefore as it is a demonstration of the differences between the Hebrew God and that of the Gentiles. The Jewish God is not the kind that destroys like heathen gods. The Hebrew God saves, makes promises to, and cares for creation.
While it appears the Jews and early Christians saw some historical significance to the story, it is difficult to say exact what that could be. Even the comments about it by Jesus and Peter are brief and in connection with a moral lesson in eschatology, employing apocalyptic language in all cases. Though the allegorical view (mixed with a chance of history) won out among Jews and Christians over the generations, the Second Awakening in the United States gave birth to a new "Dark Ages" among the new religious movements, Adventism (the father of JW religion) being one of them.
With this came the literal reading among these new movements that no rain came down on earth until after the flood (since no rain is mentioned in the Bible until then). Rejecting thousands of years of previous theology, the Jehovah's Witnesses are too self-centered in their being "the only true channel" of interpretation to test their exegetical conclusions with both history and critical scholarship.
That makes sense in the face that Jehovah's Witnesses are so uneducated that they believe the word "critical" in this sense means disapproving instead of "analytical" as it is in reference to a method of study.