Proposed Conceptual Taxonomy for Proper Identification and Classification of Tornado Events

Ernest Agee Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana

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Erin Jones Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana

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Abstract

A practical approach is recommended for identifying and archiving tornado events, based on the use of definitions that label all vortices as either type I, II, or III tornadoes. This methodology will provide a more meaningful tornado climatology in Storm Data, which separates and classifies all vortices associated in any manner with cumuliform clouds. Tornadoes produced within the mesocyclone of discrete supercell storms, with strong local updrafts (SLUs), will be classified as type I tornadoes. Frequently, these type I tornadoes result from the interaction of the SLU with strong rear-flank downdrafts (RFDs), or with shear vortices in the PBL. Tornadoes produced in association with quasi-linear convective systems (QLCS) will be classified as type II tornadoes (including cold pool, rear-inflow jets, bookend, and mesovortex events along the line). All other vortex types (including landspouts, waterspouts, gustnadoes, cold air vortices, and tornadoes not associated with mesocyclones or QLCS) will be labeled as type III tornadoes. A general discussion is provided that further clarifies the differences and categorization of these three classifications (which encompass 15 tornado species), along with a recommendation that NOAA adopt this taxonomy in operational and data archiving practices. Radar analysis and field observations, combined with storm-scale meteorological expertise, should allow for the official “typing” of tornado reports by NOAA personnel. Establishment of such a climatological database in Storm Data may be of value in assessing the effects (if any) of twenty-first-century global warming on U.S. tornado trends.

Corresponding author address: Ernest M. Agee, Dept. of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907-2051. Email: eagee@purdue.edu

Abstract

A practical approach is recommended for identifying and archiving tornado events, based on the use of definitions that label all vortices as either type I, II, or III tornadoes. This methodology will provide a more meaningful tornado climatology in Storm Data, which separates and classifies all vortices associated in any manner with cumuliform clouds. Tornadoes produced within the mesocyclone of discrete supercell storms, with strong local updrafts (SLUs), will be classified as type I tornadoes. Frequently, these type I tornadoes result from the interaction of the SLU with strong rear-flank downdrafts (RFDs), or with shear vortices in the PBL. Tornadoes produced in association with quasi-linear convective systems (QLCS) will be classified as type II tornadoes (including cold pool, rear-inflow jets, bookend, and mesovortex events along the line). All other vortex types (including landspouts, waterspouts, gustnadoes, cold air vortices, and tornadoes not associated with mesocyclones or QLCS) will be labeled as type III tornadoes. A general discussion is provided that further clarifies the differences and categorization of these three classifications (which encompass 15 tornado species), along with a recommendation that NOAA adopt this taxonomy in operational and data archiving practices. Radar analysis and field observations, combined with storm-scale meteorological expertise, should allow for the official “typing” of tornado reports by NOAA personnel. Establishment of such a climatological database in Storm Data may be of value in assessing the effects (if any) of twenty-first-century global warming on U.S. tornado trends.

Corresponding author address: Ernest M. Agee, Dept. of Earth and Atmospheric Sciences, Purdue University, 550 Stadium Mall Dr., West Lafayette, IN 47907-2051. Email: eagee@purdue.edu

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