What Are Atmospheric Rivers?

Atmospheric rivers can be both hazardous and beneficial, but before we get into that, you might wonder, what is an atmospheric river?

"An atmospheric river is just what it sounds like. It's really a river in the sky. But instead of running water, it's water vapor. And so there's these elongated plumes of water vapor in the atmosphere and when it interacts with the mountains or other topography, or sometimes even dynamics in the atmosphere and lifts up, it can produce large amounts of precipitation, which is both rain and snowfall." - Dr. Julie Kalansky

The impacts that we see from rain and snow can vary greatly depending on the intensity and duration of the storm. Because of this, the Center for Western Weather and Water Extremes created a scale for atmospheric rivers, ranging from AR 1s, which are primarily beneficial, to AR 5s, which are primarily hazardous.

For example, if we look at the 2023 water year, 38 atmospheric rivers moved into the West, and three of the stronger storms of the year were centered directly over the Central Coast. This is a big part of the reason that we saw well above average precipitation across the state. Unfortunately, because we picked up so much rainfall over such a short period of time, we did see major flooding in places like the Santa Cruz Mountains or Pajaro.

But there were also some benefits...
Thanks to the numerous atmospheric rivers during the 2023 water year, we went from 100% of the state being in drought to 0%. Additionally, because there was so much moisture in our fuels, we also had a very minimal wildfire year. Instead of burning 1.7 million acres, which is the five-year average, we burned around 320,000 with relatively few structures destroyed.
When it comes to whether the atmospheric rivers this year will be primarily hazardous or beneficial, we'll just have to wait and see, but it'll most likely be a mix of both.

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[BobUb]

nice explanation. Love that you allow complexity.

[robertforrest]

Really interesting info Holt. Here where I am we still call it the Pineapple Express... 😅

[flyingtoaster]

But should we be nervous that so much of Canada burned in 2023? And especially since that is the area that need the atmoshperic river(s)...?

[flyingtoaster]

PS/ why is meteorology framed in abstract national borders .. when the reality has to do with what we call North America?