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Overview / Storm Meteorology and Background / Records and Totals / Impacts of Storm |
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Overview A series of storms in late December 2004 through mid-January 2005 affected areas from coastal California all the way to the east coast, with the major impacts from the Front Range westward. The damage in parts of the Southwest will run into the tens of millions of dollars. More than 20 people were killed in the combination of rain and snow that impacted an enormous region with record precipitation amounts. Moisture-laden storm systems began moving off the Pacific Ocean affecting southern California from December 27th through January 13th. The rain and snow triggered flooding and mudslides and disrupted travel for much of the region. Below is a synopsis of the conditions that produced this historic precipitation event, as well as some lists of rain and snow records and a preliminary description of the major impacts. |
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Meteorology |
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As can be seen in the animated image to the left, a spinning low pressure system moved onshore from the eastern Pacific on January 7th to impact California and finally as far as the east coast later the same week. This was the second consecutive week of major storms for California. The consistent track of these storms can be blamed on a feature of the climate system colloquially known as the 'Pineapple Express'. This refers to a sub-tropical jet stream that brings moisture-laden air directly from the tropics, over the Hawaiian Islands and onto the west coast of the U.S. The moisture brought by the Pacific jet is also further squeezed out against the high topography of coastal California, in this case producing rain amounts of 5-10 inches over a large area of the state in just a few days. In the Sierra Nevada mountains the moisture was delivered as snow with over 10 feet falling across the Lake Tahoe region between December 27th and January 3rd. Nevada, Arizona and Utah also received heavy snowfall from the storms. |
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The animated image to the right (click for animation) shows accumulated 6-hourly radar estimates of total precipitation from January 7th-13th. The progression of the storm across the nation is evident on the 12th and 13th as well as its eventual exit off the east coast on the 13th and 14th. Rainfall amounts for California and other regions are described below along with impacts of the storms.
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At the beginning of 2005, the Pacific Ocean displayed signs of being in a weak El Niņo episode. A composite pattern of previous El Niņos suggests that a typical El Niņo-related precipitation pattern over the United States in winter is drier than average conditions in the Pacific Northwest and more-than-average rain and snow in the Southwest and southern California. Despite the similarity between the late December-January 2004/2005 pattern and the El Niņo composite for the West, El Niņo does not appear to be the primary contributing factor for these heavy precipitation events. According to NOAA's Climate Prediction Center, a feature of the climate system known as the Madden-Julian Oscillation or MJO, often associated with accelerating and augmenting a developing El Niņo, may have provided more moisture to the California storms. As can be seen in the image to the left showing the Pacific jet stream undercutting the high pressure ridge to its north in the Gulf of Alaska, moisture was able to be funnelled directly from the deep tropics and onshore into southern California. This pattern of the Pacific jet was influenced by the eastward movement of the MJO (and associated convection) from the western Pacific into the central Pacific and helped fuel the California storms.
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Records and Totals
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Impacts
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Useful Links
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Questions?
| For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division: |
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Climate Services Division NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4876 phone: 828-271-4800 email: questions@ncdc.noaa.gov |
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For further information on the historical climate perspective presented in this report, contact: |
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David Levinson NOAA/National Climatic Data Center 151 Patton Avenue Asheville, NC 28801-5001 fax: 828-271-4328 email: David.Levinson@noaa.gov |
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