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By Anna Skinner
Associate News Editor
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A type of storm known as an atmospheric river is bringing repeated bouts of heavy rain, strong winds and severe thunderstorms across a large portion of the U.S. this week, sparking concerns and questions about what the storm is.
Why It Matters
Earlier this week, AccuWeather meteorologists warned of a 1-in-1,000-year flood posing threats to several states. An AccuWeather spokesperson told Newsweek that floods like this have a 0.1 percent chance of happening in any given year.
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Myriad weather alerts and warnings remain in place from eastern Texas northeast through Ohio on Thursday. Meteorologists are warning of floods, severe storms and strong winds.
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What To Know
On Wednesday, the storms fueled tornadoes and heavy rain across multiple states, killing at least one person, the Associated Press reported.
In an updated report, AccuWeather warned that the "rare tropical-origin atmospheric river" would continue unleashing heavy rain and causing significant floods from the southern Plains to the Ohio Valley.
What Is An Atmospheric River?
Atmospheric rivers are a "long, narrow region in the atmosphere—like rivers in the sky—that transport most of the water vapor outside of the tropics," according to the National Oceanic and Atmospheric Administration (NOAA).
Why Meteorologists Call It A Sky River?
Atmospheric rivers are known as "rivers in the sky" because the storms are laden with moisture.
NOAA said that a strong atmospheric river can transport water vapor equivalent to up to 15 times the average water flow at the mouth of the Mississippi River. The storms are typically between 250 and 375 miles wide.
How Atmospheric Rivers Trigger Major Flooding
Atmospheric rivers can cause repeated rounds of heavy rainfall. The storms can stall over a specific area, exposing it to long-duration heavy rain that can cause significant flooding.
For the storm currently hitting the U.S., some states were anticipating four months of rain in less than a week.
Where Atmospheric Rivers Hit The US Most
The storms brought by atmospheric rivers are known for their heavy snow, heavy rain and strong winds. They more commonly affect the West Coast, particularly during the winter months.
The Science Behind The 'Pineapple Express'
The NWS describes the "Pineapple Express" as a "strong atmospheric river that is capable of bringing moisture from the tropics near Hawaii over to the U.S. West Coast."
The current atmospheric river hitting the U.S. is not considered a Pineapple Express, AccuWeather senior meteorologist Tom Kines told Newsweek, because it is originating in the Caribbean.
What People Are Saying
AccuWeather senior meteorologist Tom Kines told Newsweek: "Usually these atmospheric rivers have their origins in the tropical regions. The West Coast of the United States is famous for these, but they affect other parts of the world as well."
Kines added that the current atmospheric river is heading "into the Gulf of Mexico where it interacts with a stationary front. That's where the trouble starts. It interacts with that front and [produces] a lot of rain and severe thunderstorms with that front sitting in the same area for the next few days. That's what's raising the threat for flooding, and in some cases, maybe catastrophic flooding."
National Weather Service office in Louisville, Kentucky, in a flood watch: "This is expected to be a high end event with life-threatening flooding. Major flash flooding and river flooding will be possible. Complete any flooding preparation today."
NWS Weather Prediction Center, on X, formerly Twitter: "Life-threatening, catastrophic, and potentially historic flash flood event continues across the Lower Ohio Valley and Mid-South."
What Happens Next
The storm will continue pummeling a 1,000-mile stretch of the Midwest and South through Saturday night. River flooding could persist into early next week.
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