In every natural disaster, there is an arc to the story, the narrative. Earthquakes open with surprise. Scientists can’t predict them with the precision of hurricanes, can’t track them on radar, can’t provide much if any warning. Buildings ― rooms ― start to sway sickeningly, dishes crash. That’s how you know.

Tsunamis are more predictable. There’s warning, as there was in Japan last week. Residents in the city of Sendai had eight to 10 minutes to scramble to higher ground.

Then water converges with two properties that bring maximum devastation: speed and weight. Waves slam at up to 500 mph, the cruising speed of a jetliner. A cubic foot of seawater weighs 64 pounds. What that math means on the ground in an island nation with 18,000 miles of coastline: people, villages, every human structure, gone.

Astonishing figure: Some 2,000 bodies have washed ashore. More are expected.

Another astonishing number: Perhaps 10,000 people ― more than half the population ― are missing from Minamisanriku, a northern coastal town.

Then there are those photos of devastated villages such as Saito ― no, not a village anymore, just a mud patch with shards of furniture, toys and other detritus churned aside by the tsunami. On Thursday, a thriving place with 250 people and 70 homes. On Friday, desolation.

Most disasters unfold in a few hours, a day or two, and then recede. There’s some comfort in that, in seeing the arc end.

But in Japan’s narrative, the denouement is elusive. This disaster story keeps building, growing worse, because of the third element: nuclear suspense.

We’ve all seen the movies, and know the terrifying “China Syndrome” scenario. A crippled nuclear plant, the possibility of a core meltdown that releases massive radiation into the air and water. Will this become that? We don’t know. We see ashen-faced utility execs, telling conflicting stories about the Fukushima reactors. We watch heroic plant workers who may be exposed to large amounts of radiation in a small amount of time, attempting to douse the dangers.

Then there’s Japanese Prime Minister Naoto Kan, in epic understatement, pronouncing the situation “worrisome.” His task: Keep the disaster from submerging the world’s third-largest economy.

Those of us who live in the shadow of six active nuclear plants, who live with tornadoes, who live near enough to the New Madrid earthquake fault ― we think about these things. We’ve survived blizzards, twisters, seiches, massive thunderstorms, lethal heat waves, a leaking Chicago River, a great conflagration and many lesser but still deadly ones. No part of this nation, this world, is spared the prospect of a natural event that becomes a megadisaster.

When they occur, fear spreads fast and far: A California emergency management official, 5,000 miles from the crippled reactors, reassures residents that should a meltdown occur, “it is highly unlikely that we would see any effects of it here.”

Highly unlikely. We’d forgive residents who aren’t completely reassured by that.

But that’s the truth. Things happen that aren’t ― can’t be? ― predicted. Every failsafe can fail.

Chicagoans don’t expect more than one disaster at the same time, depending on the season. Neither did the Japanese. Richard Meserve, a former Nuclear Regulatory Commission chairman, told The Wall Street Journal that the Japanese reactors experienced a “one-two punch of events beyond what anyone could expect or what was conceived.”

Exactly: Imagination falters. Anxiety fills the void. We watch, heartbroken. We send help. We await the next chapter.

And we hope for a swift end to the story’s arc.

(The Chicago Tribune, March 16)