Extreme Weather of the Pacific
Northwest
Cliff Mass
University of
Washington

The extreme side of
Northwest weather
• The strongest non-tropical cyclones in the nation, with with the wind speeds of category 2 or 3 hurricanes.
• The greatest annual rainfalls in the continental
U.S.
• World-record snowfalls in our mountains
• Billion dollar floods
• The greatest avalanche losses in the continental
U.S.
• Localized hurricane-force winds
• and many more …

• My attempt to write a comprehensive introduction to
Northwest weather suitable for the layman.
• Includes everything from the big storms and local weather features, to climate, weather prediction and how to read the skies.
• Full of color illustrations and photos.

Thanks
• To UW Press for publishing it and the Stroum
Foundation for partially underwriting it.
• Beth Tully for her excellent work on the figures.
• Editor Mary Ribesky and Book Designer
Ashley Saleeba…among many at UW Press.
• My wife Caroline and sons Aaron and Nathan for their good natured tolerance of the project.

Washington: -48F, 118F
Oregon: -54F, 119F

The records are all east of the Cascades
On December 30, 1968 both Mazama and
Winthrop, WA dropped to -48F—the state record.
Why there?

Winthrop and Mazama are in a deep valley of the north
Cascades

The Cascades shield the valley from the warm air of the Pacific
Snow promotes cooling
Lack of clouds helps cool

Seneca and Ukiah, in the highlands of eastern Oregon, are also in a high, relatively, cloud free valley, east of the
Cascade crest.
They dropped to -54F!

The warmest temperatures are also found in eastern
Washington—but in the summer, of course.
Ice Harbor Dam: 118F
Pendleton: 119
Why are they hot?
• Isolated from cool Pacific
• Arid landscape
• Low elevation

The Banana Belt of the Southern
Oregon Coast

Brookings holds the temperature records for the Pacific Northwest every month from November through March
• Monday, December 29, 2008—75
• February 27, 1985—reached 81F, the highest temperature ever record in that month in Oregon!

Why Brookings?
Downstream from high coastal mountains

Air warms as it sinks down terrain

Extreme Northwest Precipitation

Greatest Annual Precipitation in the Continental U.S.

Annual
Precipitation
Largest Precipitation Gradients

SW Olympic Slopes-Hoh Rain Forest: 150-170 inches yr -1

Sequim: Haven for Retirees
15 inches a year— similar to LA!

Why a rain shadow?
and down the mountains!

Greatest Annual Snowfall Totals in the
World!
The Mt. Baker Ski Area in northwestern Washington
State reported 1,140 inches of snowfall for the 1998-99 snowfall season

Extreme Local Winds
February 13
1979: The
Hood Canal
Storm
Winds over 110 mph destroyed the Hood Canal Bridge
Cost to replace: over 100 million dollars

February
13
1979:
The
Hood
Canal
Storm

Inauguration
Day
Storm
January 29,
1993

The Most Extreme Northwest Windstorm: The
Columbus Day Windstorm of 12 October 1962

Max Winds
(mph)
Columbus Day
Storm 1962

Columbus Day 1962: At Cape Blanco there were
150 mph with gusts to 179! Strongest winds on bluffs and windward slopes of coastal orography

While record-breaking rain fell over the mountains of SW Washington- 20 inches over a little more of day.
Massive flooding along the Chehalis River

Landslides: which led to the retirement of the current lands commissioner

• The overwhelming majority of atmospheric
will became MUCH larger during the next decade.
• The Northwest will probably experience slower warming than much of the Northern Hemisphere, due to the nearby Pacific.

UW Press
Release Date:
November 2008 http://www.atmos.washington.edu/~cliff/weath erbook.html

Enumclaw, Washington
“Place of evil spirits”

Largest
Precipitation
Gradients

.
Sequim: roughly 15 inches per year.
Similar to Los Angeles

The Northwest Has a Mediterranean Climate

The Northwest Gets Fewer
Thunderstorms Than Almost
Anywhere in the U.S.