The Weather Notebook: Weather in Chaos

Weather in Chaos
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Dave Thurlow, Host

We can predict when the sun will rise and set. We know when Haley's comet will next streak across the night sky. So, why can't we forecast the weather with greater reliability -- three, five, ten days out into the future? Hi, I'm Dave Thurlow and this is The Weather Notebook.

Cray Y-MP Supercomputer NCAR Digital Media Catalog
Well, the answer is chaos. Not the common dictionary definition of chaos as 'utter confusion or disorder,' but chaos as scientists use it in the sense of complex, non-linear, aperiodic systems or phenomena. Think of smoke opening into tendrils as it rises from a cigarette; think of pale cream clouding a cup of black coffee. Weather happens in a similar way: there's pattern, there's a reliable limit to the range of variations, but there is never an exact duplication of conditions from one day -- or one front -- to the next.

Weather is volatile, turbulent, fluid, impossible to pin down. Even with a huge computers chunking instantaneously through mountains of pristine data, invisible error spores will pop up and mushroom so appallingly as to render any given forecast all but worthless after a week. Which is not to diminish the achievement of atmospheric scientists in our time. In half a Century, they've taken weather forecasting from the dark ages of hand-drawn maps to the brave new world of automated observations driving computer forecast models.

But the consensus in the field is that no matter how good our technology gets, the behavior of the atmosphere ten days from now will forever elude our powers of prediction. It's humbling, yet somehow also inspiring, to see science deflected by something so vast, so mysterious, so inexhaustibly chaotic as weather.

Today's contributing writer is David Laskin. The Weather Notebook is underwritten by Subaru with major support provided by the National Science Foundation.