Hurricane Hunter flights gathering data on atmospheric rivers to improve weather forecasting led by Scripps scientists in La Jolla have resumed for the winter.

Atmospheric rivers are relatively long, narrow atmospheric regions, typically several thousand kilometers long and only a few hundred kilometers wide, that transport most of the water vapor outside of the tropics. They can carry a greater flux of water than Earth’s largest river, the Amazon, and have been increasing slightly in intensity over the past century.

When an atmospheric river hits mountains, such as California’s Sierra Nevada, it is forced even higher in the atmosphere where cooler temperatures condense its vapor, rapidly transforming it into huge amounts of rain or snow concentrated over one to three days.

To better understand and forecast atmospheric rivers, “Hurricane Hunter” aircraft from the U.S. Air Force Reserve 53rd Weather Reconnaissance Squadron began flights in November over the Pacific Ocean to last through March. It is part of the Atmospheric River Reconnaissance program, led by the Center for Western Weather and Water Extremes (CW3E) at UC San Diego’s Scripps Institution of Oceanography. The program represents a research and operations partnership between science and operational weather forecasting, which ensures that methods and their impacts are continually refined and improved over time.

El “AR Recon” program collects key data on the storms as they form over the Pacific Ocean, in order to improve forecasts of where they will hit landfall and how much precipitation they will bring.

“The AR Recon partnership is a great example of state, federal, and academic collaborative research using emerging technologies to improve California’s ability to manage water with increasing weather extremes,” said Michael Anderson, state climatologist with the California Department of Water Resources. “This critical research allows for new innovative strategies for water management in a changing climate.”

Scripps field research manager Anna Wilson and meteorologist Samuel Bartlett, both of CW3E, talked about the significance of Hurricane Hunter data collection.

“We aren’t using unmanned aircraft but aircraft from the Air Force and the National Oceanic and Atmospheric Administration (NOAA) that fly into hurricanes through the summer and fall,” Wilson said. “They drop instruments into the storms themselves that measure temperature, wind, humidity, and pressure from the atmospheric river all the way down to the ocean surface.”

Asked what information gathered from the Hurricane Hunters is expected to accomplish, Bartlett said: “Initially it is to gather data on atmospheric river systems for weather modeling for 10-day forecasts. Your weather forecast is only as good as how much data you have. We’re basically giving the weather model information on where atmospheric rivers are currently.”

“Or hope is to increase the knowledge of atmospheric rivers, what to expect with the storms, and to improve the accuracy for forecasting them,” concurred Wilson. “With the data we collect, we think we can make an impact on forecasting and improve outcomes. It’s also very important as we are getting more extreme atmospheric river storm conditions with climate change. Forecasting is really important to save lives and property.”

“Forecasting for atmospheric rivers is also important from a big-picture perspective, to study the amount of rainfall and potential flooding from these storms,” concluded Bartlett.

Seven atmospheric rivers classified as strong or greater dumped rain and snow on California during the 2022-2023 rainy season, lifting the majority of the state out of drought conditions while causing disastrous flooding. This duality of promise and peril typifies atmospheric rivers, which are ribbons of water vapor in the sky that can deliver massive amounts of precipitation and make accurate forecasting essential to both water managers and public safety officials.