The DOWs will deploy at or near the coast in the direct path of the storm. "From a head-on position," says NCAR affiliate scientist, Josh Wurman, "the DOW can collect unprecedented high-resolution data and rapid-scan Doppler radar data from inside the eye."
At close range the scans will observe fine-scale but potentially damaging storm features as small as 40 feet across, including wind streaks, gusts, and other structures. The DOWs are a collaborative effort between NCAR and the Boulder-based Center for Severe Weather Research. Wurman operates the vehicles through the CSWR, with support primarily from the National Science Foundation (NSF).
The newest of the radar systems, called the Rapid-DOW, sends out six radar beams simultaneously. By raking the sky six times faster than traditional single-beam radars, Rapid-DOW can visualize three-dimensional volumes in 5 to 10 seconds and observe boundary layer rolls, wind gusts, embedded tornadoes, and other phenomena as they evolve.
Back in Boulder, NCAR scientists are running the nation's future Weather Research and Forecast (WRF) model on NCAR's IBM Blue Sky supercomputer, testing the model's skill at predicting Isabel's intensity, structures, and track. Operating on a model grid with data points only 4 kilometers (2.5 miles) apart, Blue Sky hums with calculations all night as WRF zooms in on Isabel, bringing into focus the storm's internal structure, including eyewall and rain bands. The result is a high-precision, two-day forecast. In the morning, the model starts over to create a new five-day forecast using a 10-kilometer grid and updated conditions.
NSF, NCAR's primary sponsor, supported the development of both WRF and the DOWs at NCAR. The WRF model is a cooperative effort by NCAR and several federal agencies and military branches.
"Isabel has presented an exciting opportunity," says scientist Jordan Powers, a WRF development manager at NCAR. "Resolving a hurricane's fine-scale structures in real time with this next-generation weather model is breaking new ground for forecasters and researchers."
The DOWs are pushing technological limits of their own. "The DOWs have revolutionized the study of tornadoes and other violent and small-scale atmospheric phenomena," says Wurman. The large, spinning, brightly-colored radar dishes have intercepted the eyes of five hurricanes: Fran, Bonnie, Floyd, Georges, and Lili. Data from the retired DOW1 resulted in the discovery of entirely new phenomena in hurricanes, called intense boundary layer rolls, which contain the highest and most dangerous wind gusts.
Though Powers won't be using DOW data for WRF's forecasts this week, he and others may compare Wurman's real-world observations with the model results in the future.
"It's an exciting opportunity to improve our understanding of the finer-scale structure of one of nature's most powerful phenomena," says Cliff Jacobs, program director in NSF's division of atmospheric sciences, which funds NCAR. "Federal support for national centers and the university community allows the nexus of people, tools, and ideas to converge to gain new knowledge about hurricanes. "
On the Web:
WRF background: www.ucar.edu/communications/newsreleases/2003/wrf.html
WRF forecasts: http://rain.mmm.ucar.edu/mm5; select "120h 10km Hurr WRF" or "4km Trop WRF"
DOW: http://www.cswr.org/index.html
Hurricane Isabel update: www.nhc.noaa.gov
Visuals:
DOW Images:
http://216.241.44.49/2003-0914/dow2-cropped.jpg (DOW in action)
http://216.241.44.49/2003-0914/Barrel%20updraft%20and%20DOW.jpg (DOW near a storm)
http://216.241.44.49/2003-0914/dow.smallB&W.jpg (New Rapid-DOW with small tornado)
http://216.241.44.49/2003-0914/georges.1009.d3.gif (Inside the radar eye of Hurricane Georges)
http://216.241.44.49/2003-0914/georges.0846.d3.gif (Windstreaks, gusts inside Georges)
