Assessing Real-Time Tornado Information Disseminated through NWS Products

Real-time confirmation of a tornado specified in National Weather Service (NWS) warnings and statements increases the perceived credibility and urgency of these critical warning messages to the end user, because it represents the greatest degree of certainty that the hazard exists. This timely tornado information disseminated in official NWS products and announced through multiple sources by private and public partners may help the public believe, personalize, and confirm the warning message, ultimately helping elicit an improved response to take shelter.

This study examines the frequency of NWS products that provide real-time information of ongoing tornadoes during a 5-yr period from 2007 through 2011 across the central contiguous United States, and is related to assembled tornado data of path length, duration, damage rating, spatial distribution, and time of day for each report. Overall, 40% of tornadoes were confirmed in real time. Increasing path length, duration, and intensity subsequently resulted in an increasing probability of real-time confirmation in NWS products prior to the tornado dissipating. Time of day was a factor - nighttime tornadoes were 20% less likely to receive real-time confirmation compared to daytime events. Additionally, increasing tornado forecast risk in products issued by the Storm Prediction Center produced an increasing likelihood of real-time confirmation. Analysis of these data reveals explicit cases and situations when tornadoes are more or less likely to be reported in real-time, providing some guidance when timely ground-truth information may or may not be available.