Members of Scripps’ Center For Western Weather and Water Extremes (CW3E) tour an Air Force C-130 ‘Hurricane Hunter’ aircraft at San Diego’s Brown Field. In this photo: Marty Ralph with the Air Force crew. ERIK JEPSEN/UC SAN DIEGO PUBLICATIONS

Dr. Alison Cobb of Scripps Institution of Oceanography in La Jolla is hunting atmospheric rivers with planes known as Hurricane Hunters.

More specifically, she is part of a scientific team analyzing data coming from instruments deployed by special Hurricane Hunter planes tracking atmospheric rivers. The hope is that learning more about these naturally occurring weather phenomena will make them more predictable.

“It’s just air that’s rich with moisture that moves with speed,” said Cobb, a postdoctoral scholar and research data analyst, of atmospheric rivers. “We study vapor transport through the depths of the atmosphere, these moving bands of moisture that, when they make landfall, drop a lot of rainfall or snowfall in places like the Western United States.”

Hurricane Hunter aircraft are mobilizing for an expanded 13-week period that began Jan. 5 to glean critical data for improving forecasts of atmospheric river storms over the Pacific Ocean. Such storms provide up to half of the U.S. West Coast’s annual precipitation and a majority of the flooding.

The flights are part of the Atmospheric River (AR) Reconnaissance program led by UC San Diego’s Center for Western Weather and Water Extremes at Scripps with support from the U.S. Army Corps of Engineers and California Department of Water Resources.

The program works in coordination with the National Oceanic and Atmospheric Administration’s (NOAA’s) Office of Marine and Aviation Operations and the U.S. Air Force Reserve 53rd Weather Reconnaissance Squadron “Hurricane Hunters” to execute data-collecting missions within these storms.

AR Reconnaissance includes dropondes, which are drifting buoys to collect and transmit data. “The dropondes have parachutes attached to them and are dropped from aircraft and take measurements for about 15 minutes, making observations every couple seconds,” Cobb said adding, “That way they can help with weather forecasting in real time. By putting these real observations into the weather forecasts, it improves present modeling while improving weather predictions in the future.”

Hurricane Hunter data has already proven to aid in weather forecasting.

“Some atmospheric rivers that happen every year, like the winter season in California, we’re able to predict on a longtime scale,” noted Cobb. “These rivers are dry through most of the year. They’re happening in many areas of the world. They’re important to combat drought as these rivers can be wide-ranging.”

“California experiences the greatest variability in precipitation in the country, with atmospheric river storms serving as the main driver,” said U.S. Rep. Ken Calvert (CA-42). “The AR Recon effort helps leverage our military and civilian assets to better manage that gap between drought and flooding events. Improved forecasts enhance clarity of timing, location, and severity of storms and provide great value across a range of applications from national defense to water management.”

“Research on atmospheric rivers from the Atmospheric River Reconnaissance program has helped us better predict, mitigate and optimize these weather events in California,” said U.S. Sen. Dianne Feinstein (D-CA). “Applying this data through Forecast-Informed Reservoir Operations means better flood protection and improved water storage to help lessen the effects of drought.”

Although meteorologists can see atmospheric rivers forming as much as eight days in advance, landfall forecasts can be hundreds of miles off target. AR Recon data improves forecasts of their intensity, allowing forecasters to more precisely determine potential benefits or hazards of atmospheric rivers.

“AR Recon has been a key monitoring element of the State’s Atmospheric River Research Program and is a great example of collaborative engagements that lead to improvements in precipitation prediction, providing multiple benefits to water managers seeking to understand climate change-caused weather extremes,” said Michael Anderson, state climatologist with the California Department of Water Resources.

Leading global weather models at NOAA and the National Weather Service, the U.S. Navy, and European agencies and others incorporate AR Recon data into their forecasts. In the northeast Pacific, AR Recon observations have improved precipitation forecasts over the western United States. They also provide a more accurate analysis of upstream atmospheric conditions before potential high-impact weather events develop over the central and eastern parts of the country.

“Real-time assimilation of AR Recon observations have made a significant impact, particularly for the precipitation forecasts along the west coast of the United States, with forecast improvements exceeding 20-30 percent in areas where heavy precipitation occurs due to land falling atmospheric rivers,” said Vijay Tallapragada, chief of modeling and data assimilation branch at NOAA’s Environmental Modeling Center.

Cobb agreed that Hurricane Hunter plane data has extensive scientific applications.

“It’s a huge collaborative effort that non only benefits research institutions, but also weather operational centers,” she said. “Over the past few years, we’ve seen real value in these observations, which have improved the way we look at weather forces.”