Pacific clues improve atmospheric river forecasts
Researchers have been actively trying to enhance atmospheric river forecasts by collecting targeted observations over the Pacific Ocean. Through the Atmospheric Rivers Reconnaissance (AR Recon) project, aircraft, buoys, and radiosondes gather real-time data on important atmospheric variables, which are then integrated into high-resolution weather models. This approach leads to measurable gains in forecast accuracy, improving readiness along the West Coast and supporting hydrologic planning across the country.
NOAA’s GOES-17 captured this atmospheric river stretching from the Pacific to California, an important and sometimes disastrous source of winter storms and water supply in the region Image credit: NOAA/GOES-17
For things to add up, we need to understand what atmospheric rivers really are.
Think of them as airborne highways of moisture. They are essentially long, narrow bands in the sky that move immense volumes of water. A single one can carry as much vapor as 25 Mississippi Rivers, making them major drivers of extreme rainfall and snowfall when they make landfall. The most intense atmospheric rivers can dump heavy rain and overwhelm landscapes, especially when they linger over sensitive watersheds already at risk of flooding.
Atmospheric rivers play an important role in the West Coast’s water supply. They bring much of the region’s winter moisture, helping to build up snowpacks that serve as a key source of water for agriculture and communities through the dry season.
For West Coast officials, getting ahead of these storms is essential. Not just for safety, but for managing reservoirs efficiently. Good forecasts help operators strike a balance between storing water and making room for incoming rain, reducing both risk and cost.
Speaking of the West Coast, the region experienced 56 atmospheric rivers making landfall in the 2024–2025 water year. This was an increase of five compared to previous years. Oregon and Northern California saw above-normal precipitation, while regions like Southern California received less than expected. Here is a regional breakdown of the atmospheric rivers from the Water Year 2025:
| State | Number of ARs |
| California | 79 (Northern: 43, Central: 24, Southern: 12) |
| Oregon | 47 |
| Washington | 41 |
The intensity of atmospheric rivers also increased, with 30% classified as strong or above, representing a 100% increase from 15%. This ever-growing unpredictability further fuels the need for well-refined mechanisms to manage atmospheric rivers.
How data from the Pacific is improving storm prediction
As storm after storm hit the West Coast last winter, a group of scientists turned their attention far out over the Pacific, where these powerful systems begin to form. Instead of waiting for the weather to reach land, they sent research planes and buoys into the open ocean to collect real-time data from areas that are usually blind spots in our forecasting systems.
Plugging that ocean data into forecast models made a noticeable difference, boosting short-range predictions by several days in some cases. This gave communities a head start to get ready for the upcoming bad weather. It’s a clear sign that to make sense of what arrives on our doorstep, we have to pay closer attention to what’s unfolding far offshore.
Christopher Davis, a scientist with the National Science Foundation’s National Center for Atmospheric Research (NCAR), has highlighted the fact that the targeted data collection is paying off. He explained that by gathering observations over the Pacific, scientists are able to improve forecasts of atmospheric rivers on the West Coast. Since these storms move east, the improved predictions also benefit the rest of the country.
Davis is one of the mission directors for Atmospheric Rivers Reconnaissance (AR Recon), a collaborative effort led by the Center for Western Weather and Water Extremes (CW3E) at UC San Diego’s Scripps Institution of Oceanography. AR Recon is backed by a coalition of major agencies, including the U.S. Army Corps of Engineers, California’s Department of Water Resources, the 53rd Weather Reconnaissance Squadron of the U.S. Air Force Reserve, and the National Oceanic and Atmospheric Administration’s (NOAA) Office of Marine and Aviation Operations.
Since its launch in 2016, the Atmospheric Rivers Reconnaissance program has worked to close critical gaps in storm forecasting by targeting the birthplaces of extreme weather over the Pacific. Its main objective is to give forecasters the tools to better track the intensity and path of atmospheric rivers.
This, in turn, allows emergency managers to respond sooner and reservoir operators to make more efficient water management decisions. Statistically, the AR Recon data improved three-day rainfall forecasts over California by up to 12% during the 2022 season.
Marty Ralph, the principal investigator of AR Recon, pointed out that the program helps fill a major blind spot over the Pacific. This spot is believed to be the point where these storms begin. It was noted that accurate forecasts depend on knowing a storm’s origin and movement, which is why gathering direct measurements early in their development is essential.
On the same tangent, Davis noted that each acre-foot of water in California holds big monetary value. Using accurate forecasts to guide reservoir operations could save the state millions each winter. At Lake Mendocino, where forecast-based management is already in place, this approach has cut annual costs by nearly USD 10 million, according to a 2021 report.
Davis further added that even without considering broader economic impacts, the ability to store additional water alone brings tens of millions in yearly value.
AR Recon is closing the forecast gap by looking offshore
AR Recon gathers critical data using specialized aircraft from the U.S. Air Force and NOAA, the same teams known for flying into hurricanes.
During each mission, planes release around 30 dropsondes, which are tube-shaped sensors in layman’s terms, designed to drift down by parachute while collecting real-time data on temperature, pressure, humidity, and wind. This information is instantly sent back to the aircraft and shared globally for use in forecast models. To expand on what the dropsondes capture, the aircraft also employ airborne radio occultation, a technique that tracks delays in GPS signals to reveal key atmospheric details like moisture levels and temperature.
Extending beyond aircraft missions, AR Recon expands its reach with pressure sensors added to NOAA’s ocean buoys, which already track sea surface temperatures and wave activity. As storms near the coast, the program also activates land-based stations that release weather balloons. These balloons rise to altitudes of over 35 052 m (115 000 feet), carrying radiosondes that collect detailed readings of the atmosphere. This practice is in line with the data gathered by dropsondes over the ocean.
To assess the value of specific observations, scientists use a method where they test forecasts with and without the new data. By running these parallel scenarios, they can see how much the added information shifts the forecast outcome. This approach helps them identify which regions are most worth targeting, refining their strategy for future data collection. In the field, they call this process “data denial.” It is also extremely important for the scientists to be hyper-specific with the locations they use for these observations.
While scientists prioritize tracking the most powerful atmospheric rivers that threaten West Coast regions, their work has ripple effects across the country. The storms don’t stop at the shoreline. Many evolve into major weather events further inland, from snow in the central U.S. to heavy rain in the Southeast. By compiling critical data from ocean buoys and high-altitude observations, researchers are not only improving regional forecasting but also reinforcing the accuracy of weather models nationwide.
References:
1 LOOKING TO THE PACIFIC, SCIENTISTS IMPROVE FORECASTS OF ATMOSPHERIC RIVERS – UCAR – April 17, 2025
2 The Atmospheric Rivers of Water Year 2025: April Summary – CW3E – April 22, 2025
My passions include trying my best to save a dying planet, be it through carpooling or by spreading awareness about it. Research comes naturally to me, complemented by a keen interest in writing and journalism. Guided by a curious mind and a drive to look beyond the surface, I strive to bring thoughtful attention and clarity to subjects across Earth, sciences, environment, and everything in between.
Trust and believe atmospheric rivers are nothing more than a heavy cloud seeding operation. That’s why they’re long narrow because it’s the way they spray with the planes in the upper atmosphere they just do it over the ocean so that way it accumulates even more water. They know exactly what they’re doing. It’s all designed and engineered this and these are no flukes. This is the greatest weapon in the world being utilized