A storm one meteorologist is calling “a once-in-10-year-event” is headed to California as we speak, all thanks to a phenomenon called an atmospheric river. Slated to hit California on Saturday with inches of rain and feet of snow, previous atmospheric river events have caused hundreds of millions of dollars in damage.
There’s no guarantee that the upcoming series of storms will result in similar destruction, but the forecast doesn’t look good. Much of the San Francisco area is already in a flash flood watch and Northern California is expected to receive upwards of 12 inches of rain and between 10-20 feet of snow (head over here for more on the forecast).
The warmer series of storms that will pummel California on Saturday, Sunday, Tuesday, and Wednesday is forecasted to deliver enough precipitation to flood rivers and seriously disrupt travel. Using data from the National Oceanic and Atmospheric Administration’s (NOAA) website on atmospheric rivers in California, here are four other winter storms that caused serious destruction.
What is an atmospheric river?
All of this precipitation is caused by an atmospheric river (AR), a narrow band of moisture that can transport huge amounts of water vapor towards the West Coast. Think of an atmospheric river as a fire hose that funnels moisture from the tropical Pacific towards California.
Atmospheric rivers come in many different shapes and sizes. Most of them are weak, don’t cause damage, and simply provide beneficial rain or snow that is crucial to California water supply. But when a strong AR builds and then stalls on land—as is predicted to happen this weekend and early next week—these events can cause mud slides, floods, and “catastrophic damage to life and property.” According to NOAA, 30-50 percent of the annual precipitation in the west coast states occurs in just a few AR Events.
1986 Northern and Central California
When this series of storms hit California from February 11-24 in 1986, scientists recorded huge rain totals. Bucks Lake in the Feather River Basin recorded almost 50 inches of rain, while Calistoga in Napa County measured 29 inches of rain.
The Napa River crested over 30 feet, flooding its banks at the 100-year mark. Thirteen people died in the storms, 50,000 others were displaced by the flooding, and the state recorded $400 million in damages to property and infrastructure.
1996/1997 Northern California
The atmospheric event that began on December 29, 1996 didn’t end until January 4, 1997, and it caused one of the most devastating floods in California history. Most of Northern California measured more than 24 inches of rain, and the warm nature of the storm meant that rain fell at high elevations onto saturated snowpack.
This exacerbated runoff and river flooding, and scientists measured record peak river flows on the San Joauin, Sacramento, Feather, Cosumnes, and Toulumne Rivers. Over 250 square miles of California were inundated by flood waters, causing 2 fatalities and injuring 50 people. Multiple levees along the Sacramento and San Joaquin Rivers broke due to the combination of high runoff from melting snow and heavy rainfall.
In total, the series of storms caused $1.6 billion in damages—$176 million worth in Yosemite National Park alone—destroying 20,000 homes and 1,500 businesses. The state declared a state of disaster in 43 counties, and over 120,000 people were displaced by the flooding.
2005 Southern California
From January 7-11, 2005, Southern California and specifically the city of Los Angeles received between 10-20 inches of rain. The Ventura, Santa Ynez, and Santa Clara Rivers all crested and flooded. Fourteen people died in the event, with several hundred others displaced by flooding.
The worst destruction was a major mudslide at La Conchita in Ventura County, which destroyed 15 homes and killed 10 people. In total, the entire Atmospheric River event caused between $200-$300 million in damages.
2005/2006 Northern California
This quick-moving atmospheric river event started on December 29 and brought more than 20 inches of rain throughout the Sierra Nevada. Urban areas like San Francisco recorded 24-hour rainfall totals of 5 inches on December 31 alone.
There was major flooding in the Napa and Russian River basins, with 10 counties declaring federal disaster areas. Over 1,000 homes were flooded in Napa, costing over $300 million in damages.