Characteristics of a tornado outbreak associated with the remnants of Tropical Storm Bill

On the night of July 1, 2003 the remnants of Tropical Storm Bill crossed portions of the southeastern United States. As these remnants tracked across northern Georgia and western South Carolina, they produced a tornado outbreak in eastern Georgia and southeastern South Carolina. Post-storm surveys verified 5 F1 tornadoes and 3 F2 tornadoes across eastern Georgia and southeastern South Carolina, making it the largest tornado outbreak in that area since Hurricane Earl took a similar track in 1998.

The tornadoes occurred in an atmosphere that was highly sheared, with large values of helicity, but only modest values of CAPE - a favored environment for tropical cyclone tornado outbreaks. In addition the outbreak area was in the northeast quadrant of the advancing remnant low pressure area, enhancing the potential for tornado development. Like many documented tropical cyclone tornado outbreaks, this event was characterized by several mini supercells, small shallow mesocyclones, and a surface boundary which helped increase horizontal vorticity and strengthen the low-level mesocyclones.

The paper will review this tornado outbreak, with an assessment of its synoptic and mesoscale environment within the scope of current and historical research of tornadic events associated with tropical cyclones. The presence of a mid-level dry air intrusion will also be examined, with a determination of whether it played a significant role in the magnitude and severity of the outbreak.