The 4:00 PM forecast track has Hurricane Katrina aiming for Mobile Bay, which would be Apocalypse Lite — really bad, but an order of magnitude less bad than a direct hit on New Orleans. However, the Mobile scenario is on the “east end of the guidance envelope,” according to the discussion. We could easily see some further westward drift in the NHC’s predicted track at 10:00 PM and 4:00 AM. Bottom line, the forecast is very much in flux, and it’s far too early to know where this thing is headed.

If you stop and think about it for a moment, there’s something incredibly humbling about the situation we’re in right now, watching and waiting to see where Katrina goes. A week from now, the city of New Orleans — a great, industrialized city in the most powerful nation in the history of the world — might be annihilated, or it might be devastated but not destroyed, or it might be mildly damaged, or it might be perfectly fine. We have absolutely no control over, and a very limited ability to predict, which of these scenarios will occur. We are utterly at nature’s mercy.

Which scenario occurs — annihiliation, devastation, mild damage or no damage at all — will be determined, when you boil it down to the bare essentials, by the movements of countless air and water vapor molecules through the atmosphere over the Gulf of Mexico and elsewhere. The vagaries of atmospheric dynamics will determine the fates of thousands of human beings.

A miniscule variation in the upper-level pressure gradient right now could alter Katrina’s track enough that, 72 hours from now, it ends up 100 miles east or west of where it otherwise would have been. That is more than enough to differentiate life from death, city from no city. Indeed, as Charles Fenwick points out, even 30 miles here or there can separate a close call from a direct hit. “The difference between absolute disaster, major damage…or annoyance is within the margin of forecast error at 12 hours.” Right down to the bitter end, the air molecules control our fate. If Katrina gets close enough, a last-minute “wobble” could save, or doom, the Big Easy.

If you’re a religious person, I guess those atmospheric dynamics might seem a bit less random. But then, devastating natural disasters have happened before, and they’ll happen again, so I’m not sure how comforting the idea of the Guiding Hand of God is in this situation. I tend to say things like “pray that New Orleans is spared” because I’m really not sure what else to say or do; prayer is the only thing that even has the potential to work. Anyway, supposing there is a God or some sort of higher power (which I firmly believe) and supposing He makes a habit of intervening in our everyday lives (of which I am far less certain), the fact remains that His decisions are just as inscrutable as the molecules’ random movements, and thus it’s just as humbling regardless of whose mercy we’re at: nature’s or God’s. Either way, we do not control our own destinies nearly to the extent that we like to believe.

That might sound a bit depressing, but like Casey, I find it awe-inspiring, in a way. He said it in the context of the forces that shaped the Earth billions of years ago, but it applies here too: “I find our fragility both beautiful and humbling, daunting and inspiring. We’re here because this indifferent world of ours somehow worked out just right, but we’re simultaneously subordinate to these cycles of destruction and (when lucky) creation that are much larger than any one species.”