Tornadoes without NWS Warning

Abstract

During a 5-yr period of study from 2000 to 2004, slightly more than 26% of all reported tornadoes across the United States occurred without an NWS warning being issued. This study examines some of the reasons behind why no warnings were issued with these tornadoes, and what climatological, storm classification, and sociological factors may have played a role in the lack of warnings. This dataset of tornado records was sorted by F scale, geographically by region and weather forecast office (WFO), hour of the day, month of the year, tornado pathlength, tornado-to-radar distance, county population density, and number of tornadoes by day and order of occurrence.Results show that the tornadoes most likely to strike when the public is least likely to be aware were also those tornadoes with the greatest chance of not being warned. Singular tornado events (one tornado report per day within a WFO county warning area) and the first tornado report of the day were the most difficult scenarios on which to warn, with over half of all solitary tornado events not warned. Geographic areas that experienced a significant proportion of weak, solitary, and/or nocturnal tornadoes had a much higher ratio of missed warnings. In general, the stronger the tornado, as estimated from its F-scale rating and/or track length, the greater chance it was warned. However, the tornado distance from radar had a significant impact on tornado warning statistics. In addition, many weak tornadoes were not warned, and the overall ratio of missed tornado warnings to reported tornadoes actually increased over more densely populated regions, likely due to more complete postevent verification.

A climatology of tornadic activity over Greece based on historical records

“…The frequent occurrence of tornadoes associated with damage caused in the United States is of great concern (e.g. Wyatt, 1997, 1998;Bluestein, 1999;Forbes and Bluestein, 2001;Schaefer, 2004a, 2004b;Verbout et al, 2006;Clark, 2008;Brotzge and Erickson, 2010;Hall, 2011). Brooks and Doswell (2002) mention almost 20 000 deaths associated with over 3600 tornadoes that have occurred in the United States since 1680 AD.…”

Evolution of a Quasi-Linear Convective System Sampled by Phased Array Radar

“…In addition, QLCS tornadoes do not typically produce a descending velocity signature in radar data (Trapp et al 1999). Not surprisingly, it has been suggested that many unwarned tornadoes are associated with linear systems (Brotzge and Erickson 2010).…”

“…Since the public is less aware of severe weather warnings at night (e.g., Ashley et al 2008), this secondary peak in QLCS tornado occurrence presents a significant risk. Furthermore, many nocturnal tornadoes occur without official National Weather Service (NWS) warning, due, in part, to a lack of visual observations (Brotzge and Erickson 2010).…”

Weather Radar Network Benefit Model for Tornadoes

“…Tornado warnings issued by the National Weather Service (NWS) are part of a strategy to reduce casualties by providing people with a chance to shelter in advance (Simmons and Sutter 2011). Forecasters issuing these warnings utilize multiple data sources, with Doppler weather radar serving as the most essential component (Brotzge and Donner 2013). Indeed, the nationwide deployment of the Weather Surveillance Radar-1988 Doppler (WSR-88D) improved tornado warning statistics (Bieringer and Ray 1996) that led to an estimated casualty rate reduction of ;40% (Simmons and Sutter 2005).…”