Warning Frequency Variation Among National Weather Service Weather Forecast Offices

The purpose of this research is to spatially define storm-based warning frequency for National Weather Service (NWS) Weather Forecast Offices (WFOs) in the contiguous United States. County based severe thunderstorm and tornado warnings issued from 1996 to 2006 and storm-based polygon issued from 2008 to 2010 were spatially joined to a national grid based on the United States Geological Survey 1:2400 quadrangle series. This geospatial method results in a count of the number of warnings issued for each grid cell during the time period studied. The grid cell counts were then averaged to produce annual and monthly means. These data were then statistically correlated with LandScan ambient population data and NEXRAD radar coverage. Results indicate that warning frequency does not reflect severe weather climatology. In some instances warning rates vary drastically between WFOs located in the same general area and with similar climatic conditions. Correlation results show that WFO warning frequency is not necessarily related to population distribution or radar coverage within NWS County Warning Areas. Overall results indicate that individual offices have varying culture and policies when it comes to covering severe weather and end users receive different level of service. This conclusion is not necessarily a negative, as it is expected that the local offices are intimately aware of the needs and expectations of the population in their area and warn accordingly. This local knowledge is potentially a vital part of building community resilience to extreme weather events.