For many years, National Weather Service warnings such as tornado and severe thunderstorm have been issued for entire counties at one time. Recent software enhancements, however, now allow NWS forecast offices to issue warnings using free-form graphical outlines. These outlines are translated to counties for the use of legacy dissemination systems such as the NOAA Weather Radio. However, the use of these outlines, or polygons, provide much more information to the public about the location and direction of movement of the severe weather. This new use of polygons to define weather location is an important enhancement for the NWS and lends itself well to be used in Geographic Information Systems.

A mechanism has been devised to capture this polygon information off of the text warnings issued by NWS and database the information. These polygons are then converted in near-real-time into shapefiles that can then be read into GIS applications such as ESRI's ArcView, ArcGIS, and Internet GIS applications such as ArcIMS. This paper describes the process that creates these shapefiles and shows sample output from the 2003 storm season.