Redding is having a wet Christmas with atmospheric rivers expected to continue lashing Northern California.
By the time skies clear, those storms will dump half a foot to a foot of rain on parts of Shasta County between Dec. 19 and Dec. 26, according to the National Weather Service.
A week-long series of atmospheric rivers is hitting the Pacific Northwest, said Katrina Hand at the weather service’s Sacramento branch, causing flooding throughout the Sacramento Valley, the North Coast and all the way up to Canada.
Those atmospheric rivers aren’t just regular winter storms.
What is an atmospheric river?
Atmospheric rivers are a major factor in extreme rain and snowfall in the North State and throughout the West.
Scientists coined the term in 1994 to refer to ribbons of really strong water vapor that flow within 20,000 feet of the ground.
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The Sacramento Valley’s wet/dry weather extremes are in part due to one such atmospheric river that can flow through the Golden Gate at San Francisco and up the Sacramento Valley. It then plows into the mountains north of Redding, or pushes through Burney Gap, according to Climatologist Michael Anderson.
Normal atmospheric river flow ushers in Redding’s rainy season. Without it, the area in and around Shasta County would be very dry, because the mountains in three directions would block rainfall, Anderson said.
Atmospheric rivers function much like rivers on the surface but can carry even more water than the mighty Mississippi River. The water can travel for thousands of miles.
They’re responsible for more than 90% of the water vapor transported to the mid latitudes from the tropics, according to a blog Kai-Chih Tseng wrote for the National Oceanic and Atmospheric Administration. Atmospheric rivers occur around the world but occur most often along storm tracks near jet streams, Tseng wrote.
When studying atmospheric rivers, scientists look at systems more than 1,000 miles long, less than 620 miles wide and an average of 1.8 miles in depth. Studies show they typically last around 20 hours in an area over the coast.
USA TODAY’s N’dea Yancey-Bragg, Doyle Rice, Janet Loehrke, Ramon Padilla, Dinah Voyles Pulver contributed to this story.
Jessica Skropanic is a features reporter for the Record Searchlight/USA Today Network. She covers science, arts, social issues and news stories. Follow her on Twitter @RS_JSkropanic and on Facebook. Join Jessica on Record Searchlight Facebook groups Get Out! Nor Cal , Today in Shasta County and Shaping Redding’s Future. To support and sustain this work, please subscribe today. Thank you.
This article originally appeared on Redding Record Searchlight: Redding hit by atmospheric rivers. What to know about them
Reporting by Jessica Skropanic, Redding Record Searchlight / Redding Record Searchlight
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