Perfect Storm

I've often heard the term "perfect storm" used in this sense (methaphorically, that is, not only to refer to meteorological conditions).

Perhaps SNAFU would be appropriate for this too. Although it is an acronym for Situation Normal All Fowled (explitive removed) Up, SNAFU is often used to describe a situation in which the convergeance of usually normal things have forced an unintended or unexpected consequence.

Stellar alignment, convergence and synergy come to mind.

The word "synchronicity" implies a meaningful coincidence.

http://en.wikipedia.org/wiki/Synchronicity

I think "synchronicity" implies something *too* meaningful, no? The original (to my mind wildly unscientific, but I'm sure I'd get arguments about this) meaning of the term referred to events that, while not *causally* linked, had some other, causal-*like* connection ("mystical connection" is the best I can come up with, but again this is from someone who's no fan of Jungian psychology; I'm sure there are those who would say that's a bad reading).

I don't think the term "perfect storm", "convergence" or "synergy" (or even "stellar alignment," as long as it's used with tongue in cheek) imply anything more than a genuine random coincidence of events that have an effect *as if* they'd been planned.

Perhaps too romanticized a word, but serendipity comes to mind as well, though I suppose there's an implication of fate or a "higher power" at work.

Perfect storm seems to fit the bill best.

A conspiracy of events?

What I thought of myself when I read this post was the expression, "self-fulfilling prophecy," a figure of speech meaning that a forecasted event occurs even despite when (and more specifically, because) people take action to try to avoid it.

This comes from the term "self-fulfillment," the concept that the revelation of a prediction about an event itself causes the said event to occur exactly as predicted. I sense that I may have skewed from your idea, though.

For your exact idea, "perfect storm" is a perfect expression. It also may be called a "butterfly effect" and is related to the philosophies called consequentialism and teleology.