Tornado intensity estimated from damage path dimensions.

James B Elsner,Thomas H Jagger,Ian J Elsner,Duccio Rocchini

doi:10.1371/journal.pone.0107571

James B Elsner, Thomas H Jagger + Show 2 more

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https://doi.org/10.1371/journal.pone.0107571

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Journal: PloS one	Publication Date: Sep 17, 2014
Citations: 35	License type: CC BY 4.0

Affiliation: Florida State University, University of Florida

Abstract

The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s−1 for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width.

Highlights

A tornado is a violently rotating column of air capable of producing catastrophic damage where it comes in contact with the ground
The EF scale is consistent with the original F scale but it includes additional damage indictors and it expands on the degree of damage
Tornado Damage Path Relationships The U.S Storm Prediction Center (SPC) maintains the most up-to-date and readily available record of tornadoes in the United States compiled from National Weather Service (NWS) Storm Data publications and reviewed by the U.S National Climate Data Center [12]

Summary

Introduction

A tornado is a violently rotating column of air capable of producing catastrophic damage where it comes in contact with the ground. The short duration and unpredictable nature of tornadoes together with extreme velocities make it difficult to obtain direct measurements of wind speeds within the vortex. Post storm surveys of the destruction in the wake of a tornado allow engineers to rate the damage on a scale from zero to five. The damage scale was related physically to the tornado wind speed [4,5]. Today wind speed is phenomenologically related to the observed damage [6]. The EF rating assigned to tornadoes in the historical record is the highest damage category found within the damage path [8]. Studies have addressed the need for more reliable measures of tornado winds and the potential discrepancies between wind speeds estimated by radar and damage ratings [9]

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