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Gap Winds of Juan de Fuca
Thu Oct 21, 2004
Listen in RealAudio 
Gap winds are topographically influenced winds blowing through spaces in higher
terrain. The term was first applied to winds blowing through the Strait of Juan de Fuca,
in the Pacific Northwest. Hi, I’m Bryan Yeaton, and this is The Weather Notebook.
The Strait of Juan de Fuca separates northwestern Washington from British
Columbia’s Vancouver Island; it is a slash through the mountain range that forms the
island’s backbone and Washington’s Olympic Peninsula. Its narrow, steep topography
presents a barrier to winds flowing both from the Pacific Ocean and off the continent.
As a result, winds often dramatically increase in speed when squeezed through the
gap and change their direction to follow the strait’s axis.
As the day heats under a strong sun, the wind flowing from the cool ocean to hot land
increases in speed. Some air rises over the summits, but in the Strait of Juan de Fuca,
the sea breeze squeezes right through the gap. These winds can have major impacts
on local marine traffic, not only commercial and naval vessels moving out of Seattle
and Vancouver, but also for the many pleasure craft plying the waters. When
gap-influences combine with a strong sea breeze, a placid summer afternoon on the
water can quickly become a harrowing experience, combining the high winds with
rough seas.
Gap winds can build significantly in just a few hours, at times reaching 50 knots. They
can easily surprise boaters because they arise quickly out of seemingly benign
weather conditions; and they can be very localized: in one spot you can have small-craft
warnings, or even gale warnings while surrounding waters have little wind at
all.
Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook
gets support from the National Science Foundation and Subaru of America. Find any of
our past shows online at www.weathernotebook.org.
Today's Links
Gap Winds:
http://www.suite101.com/article.cfm/13646/107207
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