Custom-built radar gave stormchasers the closest look ever at a major tornado
AMHERST, Mass.-- Tornado researchers at the University of Massachusetts, who produced the highest-resolution data ever available on a tornado during the "monster" storm that ripped through Oklahoma on May 3, will present their findings next week at the 29th International Conference on Radar Meteorology in Montreal, Canada. The meeting, sponsored by the American Meteorological Society, takes place July 12-16. Calvin T. Swift and Andrew Pazmany of the University of Massachusetts, along with Howard Bluestein of the University of Oklahoma, will present the results of the research, which is funded by the National Science Foundation.
Pazmany, an electrical engineer and research faculty member with the University's highly-regarded Microwave Remote Sensing Laboratory (MIRSL), has traveled to Oklahoma for three consecutive tornado seasons, which run roughly from April through June in the Midwest, to chase tornadoes along with colleagues at the University of Oklahoma. The May 3 storm offered him his first opportunity to see a twister close-up, as it dropped several tornadoes, one within a half-mile of the radar truck.
Pazmany records the storms with a videocamera and a specialized, truck-mounted radar unit, which he designed and built. He scans the narrow-beam radar across the tornadoes, and radar signals bounce off raindrops and flying debris, enabling scientists to track the movement of parcels of wind -- some of it blowing more than 300 miles an hour. The resulting images reveal to researchers the complex structure of a tornado.
Researchers are trying to determine what meteorological conditions enable a supercell, a large rotating thunderstorm, to drop a tornado funnel -- particularly a dangerous one. By determining what conditions must exist for the formation of an especially fierce tornado, researchers hope to develop accurate predictions of when and where such a tornado may touch down, giving people time to evacuate. Pazmany notes that "some large, organized supercells develop strong rotation, a structure similar to tornadoes, but never drop a funnel -- and no one knows why."
The specialized radar transmits at a higher frequency than the Doppler radar seen in television weather reports, Pazmany explained. It focuses in on storms with an ultra-narrow radar beam, which allows measurements of the highest wind speeds in the tornado's walls, he said. The resulting radar images reveal a shape similar to hurricanes, but on a 100-times smaller scale.
Note: Andrew Pazmany can be reached at 413-545-3495 or pazmany@mirsl.ecs.umass.edu on July 8-9; and at 1-800-441-1414, July 12-15. Images and additional data are available at http://abyss.ecs.umass.edu/tornado