Assessing the Accuracy of Tornado Watches across the Contiguous United States from 2007-2015

Gutter Bf,Brown Me

doi:10.4172/2167-0587.s6-001

Abstract

During 2007-2015, a total of 2,359 tornado watches were issued by the Storm Prediction Center and 10,840 tornadoes were confirmed. The highest concentration of tornado watches occurred in Mississippi, Alabama, Louisiana, and Arkansas. Tornado watches are issued when conditions are favorable for the development of severe thunderstorms and tornadoes over a larger-scale region. This study analyzed the accuracy of tornado watches for the nine year period of 2007-2015. In addition to accuracy, fatalities, lead times and valid watch times were calculated for each tornado watch. 58.80% of the tornado watches had at least one tornado inside the tornado watch and 27.43% had at least one tornado outside the tornado watch. Of the 10,840 tornadoes, 56.70% were inside a tornado watch, 9.69% were outside a tornado watch, and 33.62% occurred when there was no tornado watch in effect. The average valid time for a tornado watch was 6 hours and 50 minutes and the average lead time for a tornado was 2 hours and 8 minutes. Tornado watches are designed to alert the public to the potential threat to life and property, a mission of the National Weather Service. This study demonstrates the difficulty of accurately forecasting tornadoes, both spatially and temporally, as well as the significance of preparedness and mitigation strategies. It should be noted that the accuracy of tornado watches were analyzed, not the effectiveness of tornado watches.

Highlights

A tornado is defined as “a rotating column of air, in contact with the surface, and often visible as a funnel cloud and/or circulating debris/ dust at the ground” [1]
Tornado watches are issued by the SPC in Norman, Oklahoma “when conditions are favorable for the development of severe thunderstorms and tornadoes over a larger-scale region” [4]
During 2007-2015, a total of 2,359 tornado watches were issued by the SPC with 10,840 confirmed tornadoes for the same period. 2008 had the greatest number of tornadoes, tornado watches, and Particularly Dangerous Situation (PDS) tornado watches with 1,694, 405, and 22, respectively (Table 1)

Summary

Introduction

A tornado is defined as “a rotating column of air, in contact with the surface, and often visible as a funnel cloud and/or circulating debris/ dust at the ground” [1]. The United States experiences over 1,100 tornadoes per year [2]. The stated goal of the Storm Prediction Center (SPC) is to have a tornado watch issued two hours prior to the first tornado [3]. Tornado watches are issued by the SPC in Norman, Oklahoma “when conditions are favorable for the development of severe thunderstorms and tornadoes over a larger-scale region” [4]. A watch is defined by the area inside a parallelogram. Tornado warnings are issued by the local National Weather Service office (NWS) “when there is evidence based on radar or a reliable spotter report that a tornado is imminent or occurring” [4]

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