Tropical cyclone Ivan’s tornado cluster in the Mid-Atlantic region of the United States on 17–18 September 2004

Abstract

This paper presents a case study of a cluster of tornadoes produced by tropical cyclone (TC) Ivan in the Mid-Atlantic region of the United States on 17–18 September 2004. Ivan produced 118 tornadoes between 15 and 18 September, but 57 of these occurred in a period of only 10 h on the last two days. The number of tornadoes that occurred in this event is anomalous when compared to regional tornado climatology and to other TC tornado events. Furthermore, a significantly large number of the tornadoes, when compared to other TC tornadoes, were rated strong according to the Fujita Scale, and they were anomalously long- and wide-tracked. Ivan was in a synoptically favorable environment when these tornadoes were produced, and the tornadoes occurred in a favorable local-scale environment near a front with spatially overlapping shear and buoyancy.