The December 2014 North American storm complex was a powerful

winter storm A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...

(referred to by some as California's "''Storm of the Decade''") that impacted the

West Coast of the United States The West Coast of the United States, also known as the Pacific Coast, Pacific states, and the western seaboard, is the coastline along which the Western United States meets the North Pacific Ocean. The term typically refers to the contiguous U.S ...

, beginning on the night of December 10, 2014, resulting in

snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...

, and

flood watch Flood alerts are issued by weather agencies to alert residents that flood conditions are a possibility. Types of flood alerts in the United States In the United States, a flash flood watch is issued by the National Weather Service (NWS) when wea ...

es. Fueled by the

Pineapple Express Pineapple Express is a non-technical term for a meteorological phenomenon characterized by a strong and persistent large-scale flow of warm moist air, and the associated heavy precipitation both in the waters immediately northeast of the Hawaii ...

, an

atmospheric river An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the atmosphere. Other names for this phenomenon are tropical plume, tropical connection, moisture plume, water vapor surge, and cloud band. Atmospheric river ...

originating in the tropical waters of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

adjacent to the

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...

, the storm was the strongest to affect

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

since January 2010. The system was also the single most intense storm to impact the West Coast, in terms of minimum low pressure, since a powerful winter storm in January 2008. The

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

classified the storm as a significant threat, and issued 15 warnings and advisories, including a

Blizzard Warning A blizzard warning ( SAME code: BZW) is a hazardous weather statement issued by Weather Forecast Offices (WFO) of the National Weather Service (NWS) in the United States, which indicates heavy snowfall accompanied by sustained winds or frequent gu ...

for the Northern

Sierra Nevada The Sierra Nevada () is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primarily ...

(the first issued in California since January 2008).

Meteorological synopsis

Late on November 30, 2014, a weak extratropical disturbance developed at the southern end of a cold front, to the northwest of

Midway Island Midway Atoll (colloquial: Midway Islands; haw, Kauihelani, translation=the backbone of heaven; haw, Pihemanu, translation=the loud din of birds, label=none) is a atoll in the North Pacific Ocean. Midway Atoll is an insular area of the Unit ...

, near the

International Date Line The International Date Line (IDL) is an internationally accepted demarcation on the surface of Earth, running between the South and North Poles and serving as the boundary between one calendar day and the next. It passes through the Pacific O ...

. During the next few days, the system slowly developed a circulation and began to organize, while moving westward, behind a system that was already impacting the West Coast. On December 2, the storm system weakened, as it interacted with a much more powerful

Aleutian low The Aleutian Low is a semi-permanent low-pressure system located near the Aleutian Islands in the Bering Sea during the Northern Hemisphere winter. It is a climatic feature centered near the Aleutian Islands measured based on mean sea-level press ...

over the

Gulf of Alaska The Gulf of Alaska (Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, ...

, which steered the system into the northeast Pacific. On December 3, the system slowly began to restrengthen. On December 4, the system stalled off the West Coast, to the south of

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, as a ridge of high pressure built up over the northeast Pacific. During the next several days, the system gradually absorbed other incoming storms and began to rapidly intensify, attaining a minimum low pressure of on December 9. As the high pressure system off the coast of California began to break down, the storm system began bearing down on the West Coast. On December 10, the system began to impact California, even though the system was slowly beginning to weaken. Due to the anticipated flooding and other impacts, many schools across California, particularly in

Northern Northern may refer to the following: Geography * North, a point in direction * Northern Europe, the northern part or region of Europe * Northern Highland, a region of Wisconsin, United States * Northern Province, Sri Lanka * Northern Range, a ra ...

and

Central California Central California is generally thought of as the middle third of the state, north of Southern California, which includes Los Angeles, and south of Northern California, which includes San Francisco. It includes the northern portion of the San J ...

, were closed in advance of the storm. On December 11, the system moved ashore in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, but then the storm's center of circulation degenerated, and the system's low pressure center split, with the new low pressure center becoming the dominant low off the coast of

Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...

, later on December 11. Several hours later, after moving northward, the low pressure center split into 2 again, when the storm began to move ashore in the West Coast. The massive winter storm dropped large amounts of rain across California, and the system also brought powerful winds to parts of the state. The ensuing downpour triggered flash floods and power outages across the state. After moving inland, on December 12, the dominant low moved eastward across southwestern Canada, before being absorbed by the new low pressure center over

Reno, Nevada Reno ( ) is a city in the northwest section of the U.S. state of Nevada, along the Nevada-California border, about north from Lake Tahoe, known as "The Biggest Little City in the World". Known for its casino and tourism industry, Reno is the ...

, although the storm weakened to a 1004 mbar system in the process. On the same day, the system spawned an EF0 tornado 5 miles from downtown

Los Angeles, California Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...

, which was the first tornado that Los Angeles had experienced in 10 years. On December 13, the system continued moving eastward, and finally left the West Coast region. On the same day, the storm's circulation split for the second time, with the main circulation heading southeastward over

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, as the system continued to weaken. During the next day, the storm's center of circulation moved northeastward over the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

, before reaching the

Central United States The Central United States is sometimes conceived as between the Eastern and Western as part of a three-region model, roughly coincident with the U.S. Census' definition of the Midwestern United States plus the western and central portions of ...

on December 14. On December 15, the storm moved into the

Midwest The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of ...

region and began to re-intensify, developing an organized center of circulation to the southwest of the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

. Late on December 15, the winter storm's outer rainbands began impacting the states in the

Eastern United States The Eastern United States, commonly referred to as the American East, Eastern America, or simply the East, is the region of the United States to the east of the Mississippi River. In some cases the term may refer to a smaller area or the East C ...

to the west of the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

. On December 16, the winter storm's center of circulation reached the Great lakes, and the system began dropping rain and snow in New England. The system also began to produce

lake-effect snow Lake-effect snow is produced during cooler atmospheric conditions when a cold air mass moves across long expanses of warmer lake water. The lower layer of air, heated up by the lake water, picks up water vapor from the lake and rises up through ...

in the

Great Lakes region The Great Lakes region of North America is a binational Canadian–American region that includes portions of the eight U.S. states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin along with the Canadian p ...

, and in parts of New England. On December 17, the system developed a secondary low over

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

, at the end of an

occluded front In meteorology, an occluded front is a type of weather front formed during cyclogenesis. The classical and usual view of an occluded front is that it initiates when a cold front overtakes a warm front near a cyclone, such that the warm air is separ ...

, even as the main circulation continued to slowly move eastward. Later on the same day, the system's main circulation briefly stalled just north of

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

, while the secondary low continued to develop offshore. That day, rain from the storm in

Brooklyn Brooklyn () is a borough of New York City, coextensive with Kings County, in the U.S. state of New York. Kings County is the most populous county in the State of New York, and the second-most densely populated county in the United States, be ...

, combined with a poor roof, lead to an

NBA The National Basketball Association (NBA) is a professional basketball league in North America. The league is composed of 30 teams (29 in the United States and 1 in Canada) and is one of the major professional sports leagues in the United St ...

game at

Barclays Center Barclays Center is a multi-purpose list of indoor arenas, indoor arena in the New York City Boroughs of New York City, borough of Brooklyn. The arena is home to the Brooklyn Nets of the National Basketball Association and the New York Liberty o ...

being delayed 30 minutes to clean up the mess. Late on December 17, the storm system's frontal band exited the New England, even as the secondary low became the dominant low in the system, to the east of

Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and north ...

. However, the main circulation continued to persist to the east of the Great Lakes, continuing to drop lake-effect snow across New England. On December 18, the secondary low fully absorbed the original low, and the system developed into a well-defined storm off the coast of New England, before moving over

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

. Soon afterwards, the system reached a central low pressure of , after emerging into the

Gulf of Saint Lawrence , image = Baie de la Tour.jpg , alt = , caption = Gulf of St. Lawrence from Anticosti National Park, Quebec , image_bathymetry = Golfe Saint-Laurent Depths fr.svg , alt_bathymetry = Bathymetry ...

, developing into a

nor'easter A nor'easter (also northeaster; see below), or an East Coast low is a synoptic-scale extratropical cyclone in the western North Atlantic Ocean. The name derives from the direction of the winds that blow from the northeast. The original use o ...

. Afterwards, the storm slowly began to weaken, as it slowly continued moving northeastward. On December 19, the winter storm left North America, as the system began to accelerate towards the northeast. On December 20, the system was named ''Freia'' by the

Free University of Berlin The Free University of Berlin (, often abbreviated as FU Berlin or simply FU) is a public research university in Berlin, Germany. It is consistently ranked among Germany's best universities, with particular strengths in political science and t ...

, while the storm system was situated to the south of

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141220.gif On December 21, Freia underwent explosive intensification and became a bomb cyclone, dropping 30 mbars within 34 hours, attaining a minimum low pressure of .http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141221.gif On December 22, Freia weakened to a 970 mbar system, but went on to impact

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its s ...

, as well as parts of

Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...

, before stalling just southeast of

.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141222.gif On December 23, Freia split into three systems, with the main storm weakening into a 980 mbar system to the southeast of

.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141223.gif On December 24, Freia moved slightly to the west and weakened to a 990 mbar system, while the other 2 fragments of the storm continued to accelerate eastward across

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

, and

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of B ...

. On December 25, Freia weakened to a 1005 mbar storm as it entered the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

, and began to approach

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...

.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141225.gif On December 26, Freia moved inland and began to accelerate southeastward, even as the storm weakened to a 1020 mbar system.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141226.gif On December 27, Freia slightly intensified to a 1010 mbar storm as it swept southeastward into the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...

.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141227.gif On December 28, Freia was absorbed by another

extratropical cyclone Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of ...

to the north.http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20141228.gif

Impact

Damage and casualties

On December 10, due to the anticipated impacts, including flooding an blackouts, many schools in California, especially Northern and Central California, were closed in advance of the storm. Winds reached near-hurricane strength, with gusts up to while up to of rainfall in 24 hours were expected over

starting on the night of Wednesday December 10, 2014. The massive storm system was also predicted by meteorologists to have somewhat of an effect on all 48

Contiguous states The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...

. The storm claimed two victims in

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

, killed by falling trees, and left 150,000 households without power across the

San Francisco Bay Area The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Go ...

. Severe power outages in San Francisco caused

Montgomery Street Station Montgomery refers to: People For people with the name Montgomery, see Montgomery (name) Places Belgium * Montgomery Square, Brussels * Montgomery metro station, Brussels Pakistan * Montgomery (town), British India, former name of Sahiwal, Punjab ...

(one of the busiest

BART Bart is a masculine given name, usually a diminutive of Bartholomew, sometimes of Barton, Bartolomeo, etc. Bart is a Dutch and Ashkenazi Jewish surname, and derives from the name ''Bartholomäus'', a German form of the biblical name ''Barthol ...

stations in the city) to close and produced a major downtime at the

Internet Archive The Internet Archive is an American digital library with the stated mission of "universal access to all knowledge". It provides free public access to collections of digitized materials, including websites, software applications/games, music, ...

. The

San Francisco Municipal Transportation Agency The San Francisco Municipal Transportation Agency (SFMTA or San Francisco MTA) is an agency created by consolidation of the San Francisco Municipal Railway (Muni), the Department of Parking and Traffic (DPT), and the Taxicab Commission. The agen ...

announced the entire cancellation of cable cars and ferry services. Public schools remained closed on Thursday, December 11 in

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

Berkeley Berkeley most often refers to: *Berkeley, California, a city in the United States **University of California, Berkeley, a public university in Berkeley, California * George Berkeley (1685–1753), Anglo-Irish philosopher Berkeley may also refer ...

Oakland Oakland is the largest city and the county seat of Alameda County, California, United States. A major West Coast port, Oakland is the largest city in the East Bay region of the San Francisco Bay Area, the third largest city overall in the Bay A ...

and other school districts in the Bay Area. Authorities at

San Francisco International Airport San Francisco International Airport is an international airport in an unincorporated area of San Mateo County, south of Downtown San Francisco. It has flights to points throughout North America and is a major gateway to Europe, the Middle E ...

were forced to cancel 236 flights, 40% of the day's total flights cancellations in the United States. In the late morning of December 11, a tree felled by a tremendous gust of wind severely damaged the Social Hall of St Theresa Catholic Church in South Lake Tahoe, CA (El Dorado County). On the night of Thursday, December 11, the storm continued pounding

, triggering mudslides, floods, and power outages across the state. At least 24 homes in Camarillo Springs were damaged by a rockslide while over 90,000 customers remained without power.

Tornadoes

On December 12, 2014, a weak

EF0 The Enhanced Fujita scale (abbreviated as EF-Scale) rates tornado intensity based on the severity of the damage they cause. It is used in some countries, including the United States, Canada, China, and Mongolia. The Enhanced Fujita scale repla ...

tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...

struck southern

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world' ...

, the first one to strike in the city in a decade. The tornado damaged at least five homes, and cut the power to over 1,000 homes. After the winter storm moved inland, the system spawned five more EF0 tornadoes across the states of

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...

, and

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...

, from December 14-15.

December 12 event

December 14 event

December 15 event

Effects on historic drought in California

The storm provided only limited, short-term relief for California's worst drought in 1,200 years.

Lake Shasta Shasta Lake, also popularly known as Lake Shasta, is a reservoir in Shasta County, California, United States. It began to store water in 1944 due to the impounding of the Sacramento River by Shasta Dam, the ninth tallest dam in the United State ...

, the state's largest water reservoir, saw an increase in capacity from 25% to 29% on December 11. A similar increase in water level was reported in

Lake Oroville Lake Oroville is a reservoir formed by the Oroville Dam impounding the Feather River, located in Butte County, northern California. The lake is situated northeast of the city of Oroville, within the Lake Oroville State Recreation Area, in the ...

. However, experts noted that due to the soil's extreme dryness and low groundwater levels, it would take significantly more rain–at least five more similar storms–to end the drought. During the week of December 15, two more winter storms were expected to move through California during the middle of the week; however, those systems were expected to be "tame" compared to the earlier monster storm. On December 18, an additional third winter storm dropped rain across parts of the West Coast, before being absorbed by a gigantic extratropical cyclone in the

, which was forecast to move ashore the Pacific Northwest by December 21. It was also revealed that by December 18, almost all of the Exceptional Drought in

had been reduced to Extreme Drought severity, as a result of the winter storms that brought rain to California during December. After the majority of the moisture from the Pacific Northwest storm moved ashore on December 21 and 22, that storm system was absorbed by another storm on December 24, which promptly moved ashore, which caused some rainfall in California that night and early on Christmas Day. The system moved into the interior United States by Christmas Day on December 25, even as a ridge of high pressure built up off the coast of California. On December 26, the system continued to head eastward across the United States.

Notes

References

{{DEFAULTSORT:North American winter storm, 2014, 12 2014,12 Storm,2014,12 Storm,2014,12 Winter storm,2014,12 Winter storm,2014,12 Winter storm,2014,12 2014-12 Articles containing video clips

Winter storm A winter storm is an event in which wind coincides with varieties of precipitation that only occur at freezing temperatures, such as snow, mixed snow and rain, or freezing rain. In temperate continental climates, these storms are not necessar ...

Meteorological synopsis

Impact

Damage and casualties

Tornadoes

December 12 event

December 14 event

December 15 event

Effects on historic drought in California

See also

Notes

References