In western Canada, northern Europe, New Zealand and southern South America, atmospheric rivers occur on 30 to 35 days per year, Waliser said.
Though beneficial for water supplies in the western USA, these events can wreak havoc on travel, bring deadly mudslides and cause catastrophic damage to life and property, the National Oceanic and Atmospheric Administration said.
One well-known nickname for an atmospheric river is the “Pineapple Express,” which occurs when the source of the moisture is near Hawaii. A single strong atmospheric river can transport up to 15 times the water vapor compared with the average flow of water at the mouth of the Mississippi River, according to NOAA’s Earth System Research Laboratory.
This winter has been especially active for atmospheric rivers in the West, said meteorologist Jeff Zimmerman of the National Weather Service. As many as 10 separate rivers have been identified. On average, Northern California gets five to seven atmospheric rivers per wet season, the weather service said
The onslaught has knocked out the five-year drought in Northern California. Much of the Sierra Nevada saw its rainiest and snowiest October-February period on record, the weather service said.