5 facts about atmospheric rivers - the cause of this week's NorCal rain

Thanks to an atmospheric river, Northern California got some much needed rainfall this week.

An atmospheric river is a long narrow band of moisture that stretches thousands of miles across the Pacific. These series of rain storms can last up to 40 days.

When moisture transported by these storms hits the Sierra mountain range, it is forced up, cools and then condenses into generous amounts of rain or snow.

Here 5 interesting facts about atmospheric rivers:

  1. One well known type of atmospheric river is known as the "Pineapple Express." It brings moisture from the tropics near Hawaii to the Western U.S.
  2. They can transport up to 15 times the average flow of liquid water at the mouth of the Mississippi River
  3. They produce 30 percent to 50 percent of the average annual precipitation in the West Coast.
  4. In 1999, a single atmospheric river storm caused 15 deaths and $570 million in damage
  5. In 1861, rain arrived for 43 days bankrupting the state creating a mega flood - thousands died and 800,000 cattle drowned

As drought conditions for much of the state continue to be dire, the rainfall is a welcome change. This system will deliver lots of rainfall to Northern California through early Monday.


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