An Environmental Study on Tornado Pathlength, Longevity, and Width

doi:10.1175/WAF-D-20-0230.1

An Environmental Study on Tornado Pathlength, Longevity, and Width

2021-08-01

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DOI：10.1175/WAF-D-20-0230.1

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A dataset maintained by the Storm Prediction Center (SPC) of 6300 tornado events from 2009 to 2015, consisting of radar-identified convective modes and near-storm environmental information obtained from Rapid Update Cycle and Rapid Refresh model analysis grids, has been augmented with additional radar information related to the low-level mesocyclones associated with tornado longevity, pathlength, and width. All EF2-EF5 tornadoes [as measured on the enhanced Fujita (EF) scale], in addition to randomly selected EF0-EF1 tornadoes, were extracted from the SPC dataset, which yielded 1268 events for inclusion in the current study. Analysis of those data revealed similar values of the effective-layer significant tornado parameter for the longest-lived (60+ min) tornadic circulations, longest-tracked (>= 68 km) tornadoes, and widest tornadoes (>= 1.2 km). However, the widest tornadoes occurring west of -94 degrees longitude were associated with larger mean-layer convective available potential energy, storm-top divergence, and low-level rotational velocity. Furthermore, wide tornadoes occurred when low-level winds were out of the southeast, resulting in large low-level hodograph curvature and near-surface horizontal vorticity that was more purely streamwise when compared with long-lived and long-tracked events. On the other hand, tornado pathlength and longevity were maximized with eastward-migrating synoptic-scale cyclones associated with strong southwesterly wind profiles through much of the troposphere, fast storm motions, large values of bulk wind difference and storm-relative helicity, and lower buoyancy.

Keyword:

Extreme events

Mesocyclones

Storm environments

Supercells

Tornadoes

Forecasting

Forecasting techniques

Mesoscale forecasting

Nowcasting

Operational forecasting

An Environmental Study on Tornado Pathlength, Longevity, and Width

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