SAN DIEGO COUNTY, Calif. — Over the last decade, weather experts have more frequently turned to a relatively new term to explain powerful storms from the Pacific Ocean that can drop inches of rain across the state resulting in floods, mudslides, and beach erosion. That term is called, an "Atmospheric River."
CBS 8 wanted to know more about atmospheric rivers, what they are, how they work, and why they can be so potent.
To do so, we turned to the Center for Western Weather and Water Extremes (CW3E) at the Scripps Institution of Oceanography for answers on the weather phenomenon that can wreak havoc across California.
What is an 'Atmospheric River'?
An atmospheric river is a long band of water vapor that can stretch for thousands of miles, hundreds of miles wide, over the Pacific Ocean.
The weather events have been known to bring major flooding to San Diego and the region, destroying homes, and entire communities, as well as wiping out hillsides and coastal bluffs.
Julie Kalansky PhD is the deputy director at the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography. Kalansky and her team specialize in atmospheric rivers and the forces behind them.
Kalansky likens the weather events to a stream of water vapor that flows over the Pacific Ocean.
"The name, 'atmospheric river' is very fitting," says Kalansky. "It's literally a river in the sky. Instead of water in a stream, it's water vapor in an elongated flume. It travels over the ocean, and when it intersects with our mountains, it rises and can produce large amounts of precipitation, both rain and snow."
The Pineapple Express
The Pineapple Express is a narrow region of atmospheric moisture that builds up in the tropical Pacific according to NOAA. The well-known example of a strong atmospheric river gets its name because the moisture builds up in the tropical Pacific around Hawaii and can wallop the U.S. and Canada's West Coasts with heavy rainfall and snow.
Prevailing winds cross over warm bands of tropical water vapor to form this "river," which travels across the Pacific as part of the global conveyor belt. When it reaches the West Coast, the Pineapple Express can dump as much as five inches of rain on California in one day.
Are atmospheric rivers a new thing?
While the term, 'atmospheric river' is relatively new, Kalansky says they have always existed, just not studied as much as more widely known weather phenomena such as tornadoes and hurricanes.
That, says Kalansky, is where the Center for Western Weather and Water Extremes comes in.
"There could have been more attention and effort into better understanding atmospheric rivers, said Kalansky. "It didn't come about until the late 1990s. Even then, there wasn't much focus or research until recently, with our center. It's an important endeavor, and is needed to help forecast them and their strength."