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.

Keywords:

• Tropical cyclone Ivan 2004
• tropical cyclones
• tornado cluster
• North American Regional Reanalysis

Acknowledgements

The authors wish to thank Roger Edwards and one anonymous reviewer for their comments and suggestions that improved the quality of this study.

Notes

1. SBCAPE is shown here rather than the MLCAPE provided by NARR because it is better represented by this reanalysis product (Gensini et al., 2014).