Hurricanes damage is based solely on wind speed, but tornado damage is based on wind speed and suction caused by low pressure, says Horia Hangan, director of the Wind Engineering, Energy and Environment Research Institute (WindEEE) at the University of Western Ontario. "Tornadoes create pressure differentials on buildings and structures, which is perhaps what makes them so destructive," he says.

Hangan's team is conducting vortex research in the world's first twister test chamber—a $30-million, 130-ft-dia hexagonal-in-plan building, completed last year. The chamber's 106 fans have the power to produce tornadoes as strong as an EF-4.

"There's nothing like the [WindEEE Dome] anywhere," according to director Hangan.

WindEEE researchers test commercial and industrial buildings and plan to test critical structures under both horizontal—atmospheric boundary layer—wind and tornado winds to find differences in loading. The lab, which plans to have quantitative data by the end of the year, has a mission to advise new design criteria for commercial and residential standards and to find economical and robust ways to retrofit buildings.

Until more research is completed, and perhaps even after that, the best defense against fatalities is a shelter, sources agree. A recent trend is to collocate a community shelter in a building that has another primary purpose.