What are Atmospheric Rivers? Jan 11, 2017

The heavy precipitation in California is largely in part to what’s known as an atmospheric river. These periodic surges of moisture help bring 30-50% of the West Coast’s rain every year. But what are they?

Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. These columns of vapor move with the weather, carrying an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.

Although atmospheric rivers come in many shapes and sizes, those that contain the largest amounts of water vapor and the strongest winds can create extreme rainfall and floods, often by stalling over watersheds vulnerable to flooding. These events can disrupt travel, induce mudslides and cause catastrophic damage to life and property. A well-known example is the “Pineapple Express,” a strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast.

Not all atmospheric rivers cause damage; most are weak systems that often provide beneficial rain or snow that is crucial to the water supply. Atmospheric rivers are a key feature in the global water cycle and are closely tied to both water supply and flood risks — particularly in the western United States.

While atmospheric rivers are responsible for great quantities of rain that can produce flooding, they also contribute to beneficial increases in snowpack. A series of atmospheric rivers fueled the strong winter storms that battered the U.S. West Coast from western Washington to southern California from Dec. 10–22, 2010, producing 11 to 25 inches of rain in certain areas. These rivers also contributed to the snowpack in the Sierras, which received 75 percent of its annual snow by Dec. 22, the first full day of winter.

NOAA research uses satellite, radar, aircraft and other observations, as well as major numerical weather model improvements, to better understand atmospheric rivers and their importance to both weather and climate.

Scientific research yields important data that helps NOAA’s National Weather Service forecasters issue warnings for potential heavy rain and flooding in areas prone to the impacts of atmospheric rivers as many as five to seven days in advance.

To learn more about atmospheric rivers, please visit: http://www.esrl.noaa.gov/psd/atmrivers/.

Leave a comment

Your email address will not be published. Required fields are marked *


Blizzard conditions are possible from Wyoming to Minnesota Thursday and Friday with heavy snow and strong winds -… https://t.co/Mm1S7BVnjr

1 hour ago by WeatherNation

Heavy rain is falling across Florida today, but these horses are trying to make the best of the soggy ground by run… https://t.co/fuo3KIo9av

2 hours ago by WeatherNation

Heavy rain and snow continues across the West, but there is an end in sight for most areas -… https://t.co/xckrRH3ejF

3 hours ago by WeatherNation

Beijing, China saw its first winter #Snowfall Tuesday which brought and end to the winter snowfall drought. https://t.co/znmyn8ka27

4 hours ago by WeatherNation

11 Images That Show the Human Side of San Jose California Flooding & Evacuation: https://t.co/W0M1l0mrXY https://t.co/yolYhc4SZM

5 hours ago by WeatherNation

#Severe #Weather likely w/ the possibility of #tornadoes on Friday for portions of #Indiana and #Ohio. #INwx #OHwx https://t.co/3JToWXx3ne

6 hours ago by WeatherNation

On today's @WeatherNation Bolt: Flooding and evacuations continue in CA, African flooding & Chinese snow LIVE… https://t.co/A0NVDJTyDz

6 hours ago by WeatherNation

Severe thunderstorms and tornadoes are possible Friday in the Southern Great Lakes and Ohio Valley -… https://t.co/Fcx1ScrPGM

7 hours ago by WeatherNation

The #snow was falling this morning at Big Sky Resort in Montana. #MTwx @bigskyresort https://t.co/4HvPwrpJtR https://t.co/Zx2Z79xoxr

8 hours ago by WeatherNation

Winter is coming! But is it here to stay? Details: https://t.co/XAnm1akXXy

9 hours ago by WeatherNation

Dramatic footage as a group of young people fell through the ice on a pond in Central Park on Monday. They were res… https://t.co/LQOCRmkwDN

10 hours ago by WeatherNation

At least 3 more days of #record warmth is in the forecast throughout the Lower 48. Here's a peek at who will be in… https://t.co/LCBvaQCC3H

11 hours ago by WeatherNation

A new study links a springtime weather pattern and #pollution from Asia to unhealthy #ozone levels in the US. https://t.co/Tmvf1FRioW

12 hours ago by WeatherNation

Dark clouds rolled through Murray, UT yesterday. Chances of rain/ snow mixes will be possible the rest of the week… https://t.co/QlTkOM79PQ

13 hours ago by WeatherNation

Does it feel warm to you? Record heat continues across much of the Eastern U.S. Here are the records we've broken s… https://t.co/0DLnNCMMZb

13 hours ago by WeatherNation

Many California rivers and dams are running high. The Anderson Lake spillway to be implemented for the first time i… https://t.co/DUaXH9zwZ1

15 hours ago by WeatherNation

More record highs for many on Tuesday, and it's not even close to done yet: https://t.co/JZu2l6szDp https://t.co/3wDK90zvks

17 hours ago by WeatherNation

Amazing sunset in northwest #Arkansas Monday night. Photo: Joel Haskins https://t.co/dTdJHkvvVG

18 hours ago by WeatherNation

Watch as a tornado moved through this San Antonio, #Texas​ neighborhood within seconds Sunday evening. Video: Willi… https://t.co/TDB6lJucQf

19 hours ago by WeatherNation
Follow Us