A Spatial and Temporal Review of National Weather Service Impact-Based Warning Tags

The National Weather Service implemented Impact Based Warnings (IBW) in parts of the United States starting in 2013 and expanded the program to include the entire country in 2017. Impact based warnings include tags to indicate the expected hail size and wind gust magnitude (and/or tornado intensity potential) intended to clearly communicate the expected weather hazards. The spatial and temporal distribution of these tags are analyzed to show the frequency of warnings for higher end severe weather events (defined as hail two inches in diameter or greater and wind gusts of 80 mph or greater) as well as the frequency of the considerable and catastrophic tornado tags. The correlation of higher end IBW tags to vulnerable populations are also explored through the use of geospatial datasets. Preliminary verification of these events using local storm reports are conducted to assess the accuracy of the tags.