Rivers in the Sky: What are Atmospheric Rivers?

Atmospheric rivers have on the headlines as of January 2023 after causing widespread heavy rain and mountain snow in some parts of the US West Coast, especially California.

Meteorologists and weather forecasters often use the term to depict a weather phenomenon, which is massive enough to carry water vapor in long distances and cause precipitation in the form of either rain or snow.

In the past decades before the end of the 20th century, knowledge on weather forecasts, including torrential rain-causing phenomenon, relatively remained limited.

However, the early 1990s saw researchers Reginal Newell and Yong Zhu at the Massachusetts Institute of Technology (MIT) coining the term "atmospheric river" for the first time to describe the narrowness of moisture plumes in the sky.

What is an Atmospheric River?

(Photo : Photo by DAVID MCNEW/AFP via Getty Images)
In this aerial picture taken on January 14, 2023, the Salines River overflows its banks, inundating farms near Chualar, California, as a series of atmospheric river storms continues to cause widespread destruction across the state. - The latest in a damaging succession of storm systems blew into California on Saturday, bringing heavy flooding to already waterlogged regions and threatening snowfalls of up to six feet (two meters) in areas.

Atmospheric rivers are long, narrow regions in the atmospheric, comparable to rivers in the sky, that can transport majority of the water vapor outside the tropic region, according to the National Oceanic and Atmospheric Administration (NOAA).

This phenomenon carries columns of vapor which moves with the weather, carrying an amount of vapor approximately equivalent to the average water flow at the mouth of the Mississippi River, as cited by the NOAA.

When atmospheric rivers make landfall, they often release precipitation, as mentioned earlier.

The cloud band comes in a variety of shapes and sizes, wherein the ones with the largest amounts of water vapor and the strongest winds can generate extreme rainfall and floods.

One of the most notable example of a strong atmospheric river is called the Pineapple Express, which can bring moisture from the tropics near Hawaii and over to the US West Coast.

Also Read: Another Bout of Atmospheric River, Pair of Storms, Flooding Expected for California for the Weekend

What is a Pineapple Express?

One might ask if the Pineapple Express weather phenomenon comes from Hawaii, why is it calm and dry in the US island state?

According to Honolulu Civil Beat, Hawaii being at the one end of a 2,500-mile ribbon of moisture which directly struck California recently, causing riverine flooding and mudslides.

While California is on the way of a parade of atmospheric rivers of Pacific storm train, Hawaii remains from being inundated.

Another evidence explained the storm track in route to California in recent weeks pushed the ridge of a high pressure air that usually stays north of Hawaii, the Hawaii news website reported.

Related Weather Alerts

Prior and during an atmospheric river, there are several weather alerts that the National Weather Service (NWS) is issuing, which includes the following:

Hydrologic Outlook
River Statement or Special Weather Statement
Flood and Flash Flood Watch
Flood Warning
Flash Flood Warning
Flood Advisory
Flood or Flash Flood Statement

In the US, the most region affected by the tropical plume is the entire west coast of North America, including Southeast Alaska. The extreme weather events can disrupt travel and cause mudslides, as well as damage to life and property, according to the NWS.

Furthermore, the not ally atmospheric rivers are deadly and destructive; in fact, many are weak and can provide beneficial rain or high-elevation snow that is crucial to the country's water supply, the US weather agency added.