Pineapple Express is a non-technical term for a meteorological
phenomenon characterized by a strong and persistent flow of
atmospheric moisture and associated with heavy precipitation from the
waters adjacent to the
Hawaiian Islands and extending to any location
along the Pacific coast of North America. A
Pineapple Express is an
example of an atmospheric river, which is a more general term for such
narrow corridors of enhanced water vapor transport at mid-latitudes
around the world. The
Pineapple Express storms make landfall in
Washington, Oregon and
Northern California from October to April. Then
Southern California storms are
Pineapple Express storms make
landfall in late November to March.
1 Causes and effects
2 Extreme cases
2.1 West coast, 1862
2.2 Northern California, 1952
2.3 Southern California, 2005
2.4 Alaska, 2006
2.5 Pacific Northwest, 2006
2.6 Southern California, December 2010
2.7 California, December 2014
2.8 West Coast, 2017
3 See also
5 External links
Causes and effects
Madden–Julian oscillation can induce a Pineapple Express.
Pineapple Express is driven by a strong, southern branch of the
polar jet stream and is marked by the presence of a surface frontal
boundary which is typically either slow or stationary, with waves of
low pressure traveling along its axis. Each of these low-pressure
systems brings enhanced rainfall.
The conditions are often created by the Madden–Julian oscillation,
an equatorial rainfall pattern which feeds its moisture into this
pattern. They are also present during an
El Niño episode.
The composition of moisture-laden air, atmospheric dynamics, and
orographic enhancement resulting from the passage of this air over the
mountain ranges of the western coast of North America causes some of
the most torrential rains to occur in the region. Pineapple Express
systems typically generate heavy snowfall in the mountains and
Interior Plateau, which often melts rapidly because of the warming
effect of the system. After being drained of their moisture, the
tropical air masses reach the inland prairies as a
Chinook wind or
simply "a Chinook", a term which is also synonymous in the Pacific
Northwest with the Pineapple Express.
Pineapple Express events follow or occur simultaneously with
major arctic troughs in the northwestern United States, often leading
to major snow-melt flooding with warm, tropical rains falling on
frozen, snow laden ground. Examples of this are the Christmas flood
of 1964, Willamette Valley Flood of 1996, New Year's Day Flood of
1997, January 2006 Flood in Northern California,Great Coastal
2007, January 2009 Flood in Washington, and January 2012 Flood in
West coast, 1862
Early in 1862, extreme storms riding the Pineapple Express
battered the west coast for 45 days. In addition to a sudden snow
melt, some places received an estimated 8.5 feet (2.6 m) of
rain, leading to the worst flooding in recorded history of
California, Oregon, and Nevada, known as the Great Flood of 1862. Both
the Sacramento and San Joaquin valleys flooded, and there was
extensive flooding and mudslides throughout the region.
Northern California, 1952
San Francisco Bay Area
San Francisco Bay Area is another locale along the Pacific Coast
which is occasionally affected by a Pineapple Express. When it visits,
the heavy, persistent rainfall typically causes flooding of local
streams as well as urban flooding. In the decades before about 1980,
the local term for a
Pineapple Express was "Hawaiian Storm". During
the second week of January, 1952, a series of "Hawaiian" storms swept
into Northern California, causing widespread flooding around the Bay
The same storms brought a blizzard of heavy, wet snow to the Sierra
Nevada Mountains, notoriously stranding the train City of San
Francisco on January 13. The greatest flooding in Northern California
since the 1800s occurred in 1955 as a result of a series of Hawaiian
storms, with the greatest damage in the
Sacramento Valley around Yuba
Southern California, 2005
Unusually high precipitation caused an ephemeral lake to occur in the
Badwater Basin of Death Valley National Park, 2005.
Pineapple Express battered
Southern California from January 7
through January 11, 2005. This storm was the largest to hit Southern
California since the storms that hit during the 1997–98 El Niño
event. The storm caused mud slides and flooding, with one desert
location just north of
Morongo Valley receiving about 9 inches
(230 mm) of rain, and some locations on south and
southwest-facing mountain slopes receiving spectacular totals: San
Marcos Pass, in Santa Barbara County, received 24.57 inches
(624 mm), and Opids Camp (AKA Camp Hi-Hill) in the San Gabriel
Los Angeles County
Los Angeles County was deluged with 31.61 inches
(80.3 cm) of rain in the five-day period. In some areas the
storm was followed by over a month of near-continuous rain.
The unusually intense rainstorms that hit south-central Alaska in
October 2006 were termed "Pineapple Express" rains locally.
Pacific Northwest, 2006
November 2006 flood, Granite Falls on the Stillaguamish River,
Puget Sound region from
Olympia, Washington to Vancouver, BC
received several inches of rain per day in November 2006 from a series
Pineapple Express storms that caused massive flooding in
all major regional rivers and mudslides which closed the mountain
passes. These storms included heavy winds which are not usually
associated with the phenomenon. Regional dams opened their spillways
to 100% as they had reached capacity because of rain and snowmelt.
Officials referred to the storm system as "the worst in a decade" on
November 8, 2006. Portions of Oregon were also affected, including
over 14 inches (350 mm) in one day at Lees Camp in the Coast
Range, while the normally arid and sheltered Interior of British
Columbia received heavy coastal-style rains.
Southern California, December 2010
In December 2010, a
Pineapple Express system ravaged
December 15 through December 22, bringing with it as much as 2 feet
(61 cm) of rain to the
San Gabriel Mountains
San Gabriel Mountains and over 13 feet
(4.0 m) of snow in the Sierra Nevada. Although the entire state
was affected, the
Southern California counties of San Bernardino,
Orange, Riverside, San Diego, and Los Angeles bore the brunt of the
system of storms, as coastal and hillside areas were impacted by
mudslides and major flooding.
California, December 2014
In December 2014, a powerful winter storm fueled by a Pineapple
Express hit Northern California, resulting in snow, wind, and flood
watches. A blizzard warning was issued by the National Weather
Service for the Northern Sierra Nevada for the first time in
California since October 2009 and January 2008. The storm caused
power outage for more than 50,000 people. It was expected to be
the most powerful storm to impact
California since the January 2010
California winter storms. A rare tornado touched down in Los
Angeles on December 12.
West Coast, 2017
Main article: 2017
Pineapple Express storms brought flooding and
mudslides to California, particularly the San Francisco Bay Area,
destroying homes and closing numerous roads, including State Route 17,
State Route 35, State Route 37, Interstate 80, State Route 12, State
Route 1, State Route 84, State Route 9 and State Route 152.
The storm brought major snow to the Sierra Nevada and San Gabriel
Mountains. A state record was recorded with places on the Sierra
reaching up to 800 inches of snow. The storm also brought significant
flooding to the Los Angeles area and most of Southern California
killing about 3 people.
Pacific Organized Track System
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Wikimedia Commons has media related to Pineapple Express.
Pineapple Express from a website of the Mount Washington Observatory
Satellite photo of the
Pineapple Express from a University of Oregon
Animation of the Pineapp