"Each day during the Spring Experiment that was conducted from mid-April through early June, CAPS scientists applied emerging scientific methods to design a 10-member 'ensemble' of forecasts from the Weather Research and Forecasting, or WRF, software model", explained Dr. Ming Xue, director of CAPS. "Each member had a 4-kilometer horizontal resolution and covered almost the entire continental U.S. Unlike a single-model forecast, this ensemble not only predicted when and where particular weather might occur, but also the likelihood of its occurrence."

"Ensembles have been employed by larger-scale weather models before, but they've never been focused on the few-kilometer scales where individual storms actually occur", Dr. Xue continued. "The ensemble approach is exceptionally demanding when it comes to computational power and can only be accomplished on a high-performance, scalable system such as the Cray XT-based system at PSC."

Every day during the course of the experiment, terabytes (trillions of bytes) of data were generated, archived and transferred from PSC to Norman, Oklahoma, for use in forecasts, evaluations and future analysis and research. The HWT facility in Norman is strategically located in the recently built National Weather Center between the operational forecast areas of the NOAA Storm Prediction Center (SPC) and the NOAA National Weather Service Norman Forecast Office. These two offices, together with the NOAA National Severe Storms Laboratory (NSSL), led the experiment during the time of year when severe storm activity typically peaks in the region.