The prospect of more misery in a season that has already brought flooding, debris flows and power outages to parts of the state is growing by the day.
Rescuers searched for people trapped in homes or cars over the weekend. The levees failed near the river.
Much of the water used in California is supplied by winter rain and snow. When atmospheric rivers are particularly severe, they can do more harm than good, delivering too much water, too quickly, for the state to handle.
Michael Anderson, California's state climatologist, said that so far this winter's storms have been mostly in line with past ones. We are seeing a lot of big storms this year.
The storms have a narrow shape and carry a lot of water.
They form when winds over the Pacific bring warm, moist air from the tropics to the west coast. When this ribbon of water hits the Sierra Nevada and other mountains, it is forced upward and turns its water into rain and snow.
Climate scientists differentiate atmospheric rivers from other storms by the amount of water they carry. A five-point scale is used to rank atmospheric rivers.Climate Forward There’s an ongoing crisis — and tons of news. Our newsletter keeps you up to date.
Humans continue to burn fossil fuels and heat the atmosphere. The storms in California are more likely to be intense and wet. The number of atmospheric rivers that sweep through California each year and how long they last could be affected by global warming. They haven't come to a conclusion on these questions.
In a warmer atmosphere, there is more potential for it to hold water vapor. That exerts a great deal of influence.
It is important for California's weather and water supplies. The biggest floods are caused by them. The cycles of dry and wet are driven by them. They cause a lot of the state's levee breeches.
A single atmospheric river can wash away hillsides and highways. The damage is increased when several storms sweep in a matter of days or weeks.
The soils might not be able to absorb any more rain. One storm could cause rivers and streams to flood. In the high mountains, rain could cause the snow to melt and cause flooding. It is possible that emergency services could be stretched to breaking point.
It is more difficult for infrastructure to channel all that water into the ground or into a reserve when there are storms in a row.
If the storms space themselves out a week or two apart, we have time for water to move through the system.
In the winter of 1861-62, floods caused by a pile-on of wet weather swept away homes and farms, turning valleys into lakes. Scientists say the risk of a repeat of those floods is going up.
According to a study published last year, California has a 1-in-50 chance each year of experiencing a storm of comparable intensity. The odds have doubled because of climate change.
It is not known how global warming will affect the likelihood of atmospheric rivers crashing into California. Half or more of the atmospheric rivers that affected the state were part of a rapid parade of storms, according to a study done last year.
The warmer atmosphere has made it possible for California to prepare for more catastrophic rain events in the future.
He said it would act to juice up, even if that were the only thing that was happening.