Atmospheric river hits California. Here’s what that means.

As the US begins to recover from a week of turmoil, bad weather More storms are predicted as dozens have died.Ann atmospheric river began passing California on Tuesday, with another atmospheric river forecast later in the week.

Tuesday’s storm, which Matt Sitkowski, science editor of The Weather Channel, called a “impressive” example of the phenomenon, brought heavy rain and high-altitude snow to parts of the West Coast. In parts of central California, he’s already had over five inches of rain.

National Weather Service issued a flood warning Heavy rains hit much of the Bay Area Tuesday morning, causing flooding during the morning rush hour on several major highways, according to CBS San Francisco. Flood warnings have since been lifted.

A second atmospheric river is expected later this week and will continue into the weekend, Sitkowski said.

What are atmospheric rivers?

Atmospheric rivers can be life-threatening, but not all are dangerous. Most are actually beneficial, carrying rain and snow critical to water supplies, and according to the National Oceanic and Atmospheric Administration, rivers are a key feature of the global water cycle.

“Atmospheric rivers are long, narrow channels of atmospheric moisture that often extend from the tropics to high latitudes,” said Sitowski. “Those containing the largest amount of water vapor with little movement can lead to extreme flooding. This is somewhat analogous to a lake-effect snow band that hits the same place with snowfall.”

Like hurricanes, atmospheric rivers are measured in categories. The storm that hit California on Tuesday was predicted to be potentially as strong as a Category 4. The benefits of category 1 and 2 atmospheric rivers outweigh the potential hazards, and category 3 atmospheric rivers are balanced. Dangerous and useful. According to the U.S. Geological Survey, Category 4 atmospheric rivers are “mostly dangerous,” but they can also be beneficial. On the other hand, the most serious category 5 rivers are ‘primarily dangerous’.

On average, the West Coast receives 30% to 50% of its annual precipitation through atmospheric rivers, according to NOAA. An airy river called the Pineapple Express carries moisture from the Hawaiian region to the West Coast. According to NOAA, storm systems can bring up to five inches of rain or snow in a single day.