As we enter the hurricane season, it’s important to remember that such storms are not the only wind-driven catastrophes threatening communities, businesses and their insurers. Indeed, average annual aggregate losses from severe thunderstorms and the tornados they spawn are roughly comparable to average annual aggregate losses from hurricanes.
Case in point: At 9:45 p.m. on Friday, March 14, downtown Atlanta, Ga., experienced its first tornado since record-keeping began in the late 1800s. The storm, one of a series to hit the Southeast that weekend, touched down near Vine City, a neighborhood in west Atlanta, and then moved to the city center, where it knocked out power to 19,000 customers.
The storm also blew out skyscraper windows, ripped furniture from hotel rooms, and severely shook the packed Georgia Dome. It then slammed into another residential area directly east of downtown.
When it was all over, the twister had cut a path six miles long and 200 yards wide in some places.
Classified as an EF2 event on the Enhanced Fujita scale, it brought gusts up to 135 miles-per-hour. The severe thunderstorm system that spawned it also brought hail and torrential rains.
Within days of the event, an AIR survey team arrived to assess the damage. Based on published reports and a tornado track map prepared by the National Weather Service, the team targeted four regions of interest: the touchdown point in Vine City, Atlanta’s downtown, Cabbagetown and the Cotton Mills lofts, and the end point near Braeburn Circle.
The NWS tornado track included two “red zones,” or sections of heavy damage, separated by approximately one mile. This variation in damage is not untypical, as tornadoes usually undergo periods of weakening and reintensification along their path.
In the case of the Atlanta tornado, another factor was that the damage was enhanced in neighborhoods where the built environment was densest—that is, where more debris could be accumulated by the tornado, increasing its damage potential.
To fully understand the damage patterns that resulted, the AIR team surveyed not only structures in the tornado’s path, but also sites outside its perimeter.
The team began surveying damage at the touchdown point—a residential area west of the city’s business district. The area is dominated by one- and two-story single or multifamily homes with wood frame construction and asphalt shingle roofs. Most are old, and many are not well maintained.