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 the wind speeds of some equivalent to
category 1 or 2 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 …
The Book
• 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.
• 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.
Northwest
Temperature
Extremes
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
northeast
Cascades
The Cascades shield the valley from the
warm air of the Pacific
Snow promotes cooling
Lack of clouds helps cool
Wintertime low clouds in eastern Washington
Seneca and Ukiah, in the highlands of eastern Oregon, are
also in high, relatively, cloud free low spots, east of the
Cascade crest.
They have dropped to -54F!
The warmest
temperatures are also
found in eastern
Washington—but in the
summer, of course.
Ice Harbor Dam: 118F
Pendleton: 119F
Why are they so hot?
•Isolated from the cool Pacific
•Arid landscape
•Low elevation
The Banana Belt of the Southern
Oregon Coast
Brookings
Brookings holds the temperature
records for the Pacific Northwest
every month from November
through March
• February 27, 1985—reached 81F, the
highest temperature ever record in that
month in Oregon!
• Recent warm example: Monday, November
29, 2008—75
February 27, 1985
Maximum Temperatures
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.
Largest Precipitation Gradients
Annual
Precipitation
SW Olympic Slopes-Hoh Rain Forest: 150-170 inches yr-1
Sequim: Haven for Retirees
15 inches a year—
similar to LA!
Why suchWhy
large
contrasts?
a rain
shadow?Air moving up
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
The most costly
extreme weather of
the Northwest:
Flooding
Most are associated with the
“Pineapple Express”
A relatively narrow current of warm, moist air from the
subtropics…often starting near or just north of Hawaii.
a.k.a.
Atmospheric
rivers
A Recent Devastating Pineapple Express:
November 6-7, 2006
Dark Green: about 20 inches
Mount Rainier National Park
18 inches in 36 hr (Nov 8, 2006)
Mt.
Rainier
damage
December 2-3, 2007
15-20 inches
of rain
Dec. 3, 2007
20 inches in two
days over coastal
terrain of SW
Washington
The results:
massive
landslides
and river
flooding
As storm with political
implications….
Doug Sutherland
Sometimes damaging NW rains are very localized:
December 13, 2006: The Madison Valley Storm
Nearly 1 inch in an hour
Thunderstorms and narrow
valleys
Heppner, Oregon
June 14, 1903
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
The Hood Canal Storm
February
13
1979:
The
Hood
Canal
Storm
Enumclaw, Washington
“Place of evil spirits”
Enumclaw and nearby foothills locations
can experience severe
windstorms…while calm winds occur a
dozen miles away
Winds over 118 mph
December 24, 1983
December 24, 1983
Why Enumclaw?
Enumclaw Windstorm Pressure
Pattern
December 28,
1990
December 24, 1983
Fraser River Gap Windstorms
December 28, 1990
Fraser River NE Gap Flow
Gusts
above 90
mph
Max Winds, 28 Dec. 1990
December 28, 1990
The region’s
most extreme
Inauguration
weather is
Day
Storm
associated
January 29,
1993
with large low
pressure areas
from off the
Pacific
1993 Inauguration Day Storm
Inauguration Day Storm
Sea Level Pressure analysis
Northwest Cyclones
• Our storms are midlatitude cyclones…areas
of intense low pressure that derive their
energy from the the north-south variation of
temperature in the midlatitudes.
• In contrast: tropical cyclones…like
hurricanes… get their energy from the
warm sea surface of the tropics.
1000 miles
1000 miles
Hurricane Ivan
Our storms are bigger than theirs!
Trees—our force multiplier
Wimpy Tropical Palms
The Most Extreme Northwest Windstorm: The
Columbus Day Windstorm of 12 October 1962
Max Winds
(mph)
Columbus Day
Storm 1962
Probably the
most intense
non-tropical
cyclone to hit
the continental
U.S. in a
century
Columbus Day 1962: At Cape Blanco there were
150 mph with gusts to 179. Strongest winds on
bluffs and windward slopes of coastal orography
The Great
Coastal Gale
of December
3-4, 2007
A very unusual windstorm
Hurricane-force winds
sustained for nearly 24-h
Flooding over the coastal
mountains
Northern Oregon coast
Near Route 26 in Oregon
4 AM
Dec 3
2007
Is Northwest weather getting
more extreme?
• Will global warming cause more floods and
storms?
• Will storms get more intense?
Certainly, there has
been a lot of such
talk in the media
and elsewhere
From “when it rains it pours”
…but heavy rains are becoming less frequent in Oregon.
Windstorm Trends
…and interestingly, the number of major
windstorms is decreasing in Oregon.
Source: Brigit Dotson, UW M.S. Thesis
Initial High Resolution Climate Simulations
Why Simple
Arguments Could
Fail
• A number of theoretical, modeling, and
observational studies have suggested that the jet
stream may move northward under global
warming.
• Strong storms and heavy rainfall (pineapple
express situations) tend to follow the jet stream.
• It is possible that the “action” could move north of
us under GW, with less major storms.
Bottom Line
• The atmospheric sciences community is not
yet sure whether global warming will
produce a change in extreme weather
frequency or intensity over the Northwest.
• This is an area of active research and we
should know a lot more in five years.
• Until then, be wary of simplistic, dire
predictions.
The End
Mercer Island: Hanukah Eve Storm