The Tornado Outbreak across the North Florida Panhandle in association with Hurricane Ivan

Hurricane Ivan made landfall early on the morning of 16 September 2004 just west of Gulf Shores, Alabama as a category 3 hurricane on the Saffir-Simpson Hurricane Scale. Approximately 111 tornadoes were reported associated with Ivan across the southeast United States. Eight people were killed and 17 were injured by tornadoes. The most significant tornadoes occurred as hurricane Ivan approached the Florida Gulf coast on the afternoon and evening of 15 September.

The intense outer rain bands of Ivan produced numerous supercells over portions of the Florida Panhandle, Big Bend, southwest Georgia, and Gulf coastal waters. In turn, these supercells spawned dozens of tornadoes. An elderly man was killed by an F1 tornado, which touched down on Panama City beach and moved across a heavily populated area of Panama City. The tornado was caught on the WJHG-TV tower cam. A short time later, a second F1 tornado touched down in southeast Bay County killing one person when a wood frame house was destroyed. Later that evening, F0, F1 and F2 tornadoes touched down in Franklin, Liberty, Calhoun, and Jackson Counties; all spawned from the same parent supercell. Four people were killed when their mobile homes were destroyed near Blountstown, Florida.

Overall, there were 23 tornadoes reported across the National Weather Service (NWS) Tallahassee forecast area. The office issued 130 tornado warnings from the afternoon of 15 September until just after daybreak on 16 September.

The paper examines the convective cells within the rain bands of hurricane Ivan, which produced these tornadoes across the Florida Panhandle and southwest Georgia. The structure of the tornadic and non-tornadic supercells is examined for clues on how to better warn for these types of storms. We are currently in the process of examining nearly every mesocyclone identified by WSR-88D over land in the WFO Tallahassee County Warning Area. So far, all tornadoes reported were associated with nondescending type mesocyclones, which offer few advanced indications that a tornado is forming. The presentation will also focus on the short-term predictability of these dangerous storms, and examine the problem of how to reduce the false alarm rate, while still maintaining a high probability of detection.