UW News

November 29, 2001

Unraveling the secret of Pacific Northwest storms

News and Information

The Pacific Northwest’s fabled rainy season typically starts in November. This year Cliff Mass is counting on the storms to give up some of their secrets and help researchers develop more precise forecasts for precipitation and flooding.

Mass will team with other UW researchers and those from a number of regional and national institutions to gather detailed precipitation information over a 35-mile segment of the Cascade Mountains in west-central Oregon.

From now through Dec. 22, research aircraft will crisscross the area between Mount Jefferson and North Sister Mountain in the second phase of a project designed to improve computer models that meteorologists use in weather forecasting. The models have been used in recent years to devise more finely tuned forecasts, but it has become apparent there are problems with the way the models deal with clouds and precipitation, Mass said.

“It’s a serious problem that we haven’t been able to fix because we lack sufficient data about what’s happening in the real world,” he said.

The first phase of the project was conducted earlier this year along the Washington coast around Westport, gathering data as Pacific storms came ashore.

In the second phase, researchers will examine what happens as the clouds drop their moisture over the mountains. The region selected for the research, around Santiam Pass, appears to be ideal because the terrain is fairly simple, air traffic is light and the area is dependably wet during the winter. The area receives an average of 0.4 inch of precipitation a day between Nov. 10 and Jan. 25.

“The mountains are a wonderful laboratory because their influence on weather systems is so predictable,” Mass said. “You know it’s going to be wet on one side and dry on the other. That allows us to position critical observing systems where they can do the most good.”

In addition to the UW, the work is being conducted by the National Weather Service, the Navy, the National Center for Atmospheric Research, the Pacific Northwest National Laboratory, the University of Utah, the National Oceanic and Atmospheric Administration and the State University of New York at Stony Brook.

UW atmospheric scientist Peter Hobbs will lead researchers collecting a variety of measurements from aboard a Convair 580 research aircraft, called Husky One, which Mass characterized as “probably the best platform in the world for studying cloud physics.”

In addition, NOAA will provide a P-3 Hurricane Hunter aircraft with power Doppler radar units, and scientists will use surface-based radar and other equipment to glean information from the winter storms.

“We have an impressive collection of assets coming in,” Mass said. “With the knowledge we gain from this experiment, we hope to substantially improve the precipitation forecasts made by computer models, which will bring higher-quality warnings of heavy rain and flooding.”

The work is being paid for primarily with a grant from the National Science Foundation. The National Weather Service and the U.S. Department of Energy provided additional funding. Details about the project can be found at http://improve.atmos.washington.edu/.