Pineapple Express
Encyclopedia
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
and extending to any location along the Pacific coast of North America. A Pineapple Express is an example of an atmospheric river
Atmospheric river
An atmospheric river is a narrow corridor or filament of concentrated moisture in the atmosphere. Atmospheric rivers consist of narrow bands of enhanced water vapor transport, typically along the boundaries between large areas of divergent surface air flow, including some frontal zones in...
, which is a more general term for such narrow corridors of enhanced water vapor transport at mid-latitudes around the world.
Causes and effects
A Pineapple Express is driven by a strong, southern branch of the Polar jetstreamJetStream
JetStream and Mobile JetStream are two former brand names used by Telecom New Zealand to market its retail and resale ADSL-based fixed line and CDMA2000-based 3G wireless Internet access offerings respectively...
and is usually marked by the presence of a surface frontal
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
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
Madden-Julian oscillation
The Madden–Julian oscillation ' is the largest element of the intraseasonal variability in the tropical atmosphere. It is a large-scale coupling between atmospheric circulation and tropical deep convection...
, 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
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
causes some of the most torrential rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
s 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
Chinook wind
Chinook winds , often called chinooks, commonly refers to foehn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest.Chinook is claimed...
or simply "a Chinook", a term which is also synonymous on the Coast with the Pineapple Express.
Extreme cases
Many 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 1964Christmas flood of 1964
The Christmas flood of 1964 was a major flood that took place in the Pacific Northwest of the United States between December 18, 1964 and January 7, 1965, spanning the Christmas holiday.Considered a 100-year flood,...
and the Willamette Valley Flood of 1996
Willamette Valley Flood of 1996
The Willamette Valley Flood of 1996 was part of a larger series of floods in the Pacific Northwest of the United States which took place between late January and mid-February, 1996. It was Oregon's largest flood event in terms of fatalities and monetary damage during the 1990s...
.
2005
A Pineapple Express battered Southern CaliforniaSouthern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
from January 7 through January 11, 2005. This storm was the largest to hit Southern California since the El Niño of 1998. The storm caused mud slides and flooding, with one desert location just north of Morongo Valley receiving about 9 inches (22.9 cm) of rain, and some locations on south and southwest-facing mountain slopes receiving spectacular totals: San Marcos Pass
San Marcos Pass
San Marcos Pass is a mountain pass in the Santa Ynez Mountains in California.It is traversed by State Route 154. The pass connects Los Olivos and the Santa Ynez Valley with Santa Barbara, California...
, in Santa Barbara County, received 24.57 inches (62.4 cm), and Opid's Camp in the San Gabriel Mountains
San Gabriel Mountains
The San Gabriel Mountains Range is located in northern Los Angeles County and western San Bernardino County, California, United States. The mountain range lies between the Los Angeles Basin and the Mojave Desert, with Interstate 5 to the west and Interstate 15 to the east...
of 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.
2010
In 2010, a Pineapple Express system ravaged much of California from December 17 through December 22, bringing with it as much as 2 feet (61 cm) of rain to the San Gabriel Mountains and over 13 feet (4 m) of snow in the Sierra Nevada. Although the entire state was affected, the Southern California counties of San Bernardino, Orange, 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.Alaska, 2006
The unusually intense rainstorms that hit south-central Alaska in October 2006 were termed "Pineapple Express" rains locally.Puget Sound, 2006
Puget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
region from Olympia, Washington
Olympia, Washington
Olympia is the capital city of the U.S. state of Washington and the county seat of Thurston County. It was incorporated on January 28, 1859. The population was 46,478 at the 2010 census...
to Vancouver, BC received several inches of rain per day in November 2006 from a series of successive 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 full capacity due to 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 Lee's Camp in the Coast Range, while the normally arid and sheltered Interior of British Columbia received heavy coastal-style rains.
Northern California, 1952
The San Francisco Bay AreaSan Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
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 Area.
The same storms brought a blizzard of heavy, wet snow to the Sierra Nevada Mountains, notoriously stranding the streamliner City of San Francisco
City of San Francisco
The City of San Francisco was a streamlined passenger train operated jointly by the Chicago and North Western Railway, the Southern Pacific Railroad, and the Union Pacific Railroad...
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
Sacramento Valley
The Sacramento Valley is the portion of the California Central Valley that lies to the north of the San Joaquin-Sacramento Delta in the U.S. state of California. It encompasses all or parts of ten counties.-Geography:...
around Yuba City
Yuba City, California
Yuba City is a Northern California city, founded in 1849. It is the county seat of Sutter County, California, United States. The population was 64,925 at the 2010 census....
.
External links
- Pineapple Express from a website of the Mount Washington ObservatoryMount Washington ObservatoryThe Mount Washington Observatory is a private, non-profit scientific and educational institution organized under the laws of the state of New Hampshire. The weather observation station is located on the summit of Mount Washington in New Hampshire...
- Satellite photo of the Pineapple Express from a University of OregonUniversity of Oregon-Colleges and schools:The University of Oregon is organized into eight schools and colleges—six professional schools and colleges, an Arts and Sciences College and an Honors College.- School of Architecture and Allied Arts :...
website - Animation of the Pineapple Express by NASA