Our East Coast Fall

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Foliage along Alaskan Way

Seems like everyday for at least a month when I’ve walked out my door, I’ve been struck by spectacular fall foliage -- the kinds of red, golds and oranges I remember from my years in the Midwest and on the East Coast, and have never really gotten over missing. I’ve had to wonder: Am I imagining this? After 16 years in Seattle, have I finally gotten acclimated to our subtler hues, which I’m now finding remarkable? Turns out, my eyes are not deceiving me. The University of Washington’s Department of Atmospheric Sciences has noticed the atypically gorgeous colors as well, which have been a subject of chatter at its weekly weather meetings.

“It’s the nicest fall I can remember, and I’ve been here 21 years,” says Dale Durran, chair of the department.

The reason is our unusually dry and cloudless weather this fall (kind of makes up for our crappy early summer). The brightest foliage colors come when the nights are cool and the days are warm, explains Mark Stoelinga, an Atmospheric Sciences professor. This “diurnal effect” stimulates the chemical process that turns leaf color. Clouds hamper this effect because they act like a blanket at night, stopping heat from radiating upwards, and a barrier during the day, preventing the sun from permeating downwards. And we usually have a lot of clouds come September and October, although blessedly not this year (today being an exception).

Dry weather is also conducive to the chemical changes that produce foliage color. Also, Stoelinga says, "rain can knock the leaves off the trees and they make things more miserable generally so that you don’t realize the colors. All you see are wet, rotting leaves on the ground.” The early season windstorms we typically have, but not this year, also steal the leaves from the trees.

Enjoy it while you can. No long-term atmospheric changes have taken place to ensure repeat performances. “You can’t attribute this to global warming,” Durran says. At least for now, though, the weather professors are staring out their windows toward leafy Portage Bay, soaking it all in.

 
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