page_title: January 2010 North American winter storms
section_title: Meteorological History
hierarchical_section_title: January 2010 North American winter storms / Meteorological History
caption_attribution_description: English: Satellite image of the sixth of the January 2010 North American winter storms (the fifth storm to affect California), at peak intensity, just prior to landfall in California on January 21. This storm was the last storm of the group to affect California, and it also broke multiple minimum pressure records across California and Oregon, and it was the most powerful winter storm to strike the Southwestern United States in 140 years.
context_page_description: The January 2010 North American winter storms were a group of seven powerful winter storms that affected Canada and the Contiguous United States, particularly California. The storms developed from the combination of a strong El Niño episode, a powerful jet stream, and an atmospheric river that opened from the West Pacific Ocean into the Western Seaboard. The storms shattered multiple records across the Western United States, with the sixth storm breaking records for the lowest recorded air pressure in multiple parts of California, which was also the most powerful winter storm to strike the Southwestern United States in 140 years. The fourth, fifth, and sixth storms spawned several tornadoes across California and Arizona, with at least 6 tornadoes reported in California and another tornado reported in Arizona; the storms also spawned multiple waterspouts off the coast of California. The storms dumped record amounts of rain and snow in the Western United States, and also brought hurricane-force winds to the U.S. West Coast, causing flooding and wind damage, as well as triggering blackouts across California that cut the power to more than 1.3 million customers.
context_section_description: From January 14 to 15, 2010, six extratropical disturbances developed over the north Pacific, within a large trough of low pressure, from the waters south of the Aleutian Islands to the east coast of Japan. Strengthened by an atmospheric river, a powerful jet stream with winds reaching 230 mph (370 km/h), and the most powerful El Niño event (the fourth-strongest one on record) since 1997–98, the storms quickly developed while accelerating eastward. On the afternoon of January 16, the first storm reached the Pacific Northwest. On the same day, a seventh, small cyclone developed to the northwest of the first storm, which looped northwestward into the Gulf of Alaska for a few days, before dissipating on January 19. The first storm moved ashore British Columbia on the afternoon of January 17, impacting the Pacific Northwest, before dissipating early on the next day, ending the first wave of storms. 
  On the afternoon of January 17, the second storm, the first of five powerful storms to impact California, reached the West Coast of the United States, beginning a week of heavy rainfall and powerful gale-force winds. The storm was steered northeastward by a blocking ridge of high pressure over the Central United States, and made landfall on British Columbia on January 18, before dissipating late that day. As the second storm moved inland, the third storm arrived at the U.S. West Coast on January 18, bombing out and reaching a peak intensity of 964 millibars (28.5 inHg) at 18:00 UTC (10:00 a.m. PST) that day. Afterward, the third storm weakened and stalled of the coast of the Pacific Northwest while the fourth storm approached, which reached the U.S. West Coast on January 19. The fourth storm began a small tornado outbreak in California on January 19, which would last until January 21, and the fourth storm also spawned four waterspouts off the coast of Southern California. On the afternoon of January 19, the National Weather Service issued two tornado warnings for San Diego County within hours of each other. The third storm absorbed the fourth storm on January 20, restrengthening somewhat in the process. The third storm then moved into the Gulf of Alaska for another few days, before dissipating on January 23.
  On January 20, the fifth storm, the fourth storm to affect California, reached the West Coast of the U.S., beginning the third and final wave of storms. The storm intensified as it neared the coast of Oregon, reaching a peak intensity of 970 millibars (29 inHg) as it approached the coast of Northern California. The fifth storm then moved northward and weakened, stalling over the northeast Pacific for another several days, before being absorbed into another approaching extratropical cyclone late on January 24.
  On January 21, the sixth storm (the fifth and final storm to affect California) reached the West Coast of the U.S. The storm rapidly intensified as it approached California, reaching a peak intensity of 973 millibars (28.7 inHg) that afternoon, just prior to making landfall on California near San Francisco. This made the storm the most powerful winter storm to strike the Southwestern United States in 140 years. The storm also tapped into the Pineapple Express, boosting the amount of moisture in the storm. The storm broke low pressure records across California and Oregon as it moved inland, with a minimum pressure of 978 millibars (28.9 inHg) recorded in Eureka, California, and a minimum pressure of 987 millibars (29.1 inHg) recorded in San Diego County. The storm also produced an EF-0 tornado in Ventura, California, as well as numerous waterspouts across Southern California. The powerful winter storm weakened as it moved inland, but continued to affect California until January 23. The ridge of high pressure previously stationed over the Central U.S. had broken down by then, allowing the powerful storm to move eastward across the mainland United States, with the storm expanding in size as it moved eastward. The sixth storm reached the Eastern United States on January 24, bringing rain and snow to the region. Over the next
caption: Satellite image of the sixth storm (the fifth storm to affect California) at peak intensity on January 21, shortly before landfall
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