Hazard field

The Convective Hazard Field depicts areas of aviation hazard due to convective storms.  The hazard field is based on WSR-88D National Radar Mosaics and National Lightning Detection Network (cloud-to-ground) data.  The following pages document the methodology used to calculate the Convective Hazard Field.

Quality Control - Thresholding radar data based on Echo Tops

The above image is the South-Central zoom of the national mosaic composed from the WSR-88D radars. Single click on this image to toggle between the radar and echo tops data.  

The echo tops data are used to threshold the Vertically Integrated Liquid Water (VIL) radar data.  The VIL data are provided in the NIDS WSR-88D product stream and are mapped to a national mosaic by UNISYS.  The VIL field is calculated by using an empirical formula to derive liquid water content from radar reflectivity at each elevation.  The data are then integrated with height to obtain VIL.  The VIL data provides information about the intensity of the storm throughout it's vertical extent as well as providing a proxy for vertical development.  

The first step in creating the hazard field is to eliminate radar data where the echo tops are less than 17,000 ft. This step removes ground and Anomalous Propagation (AP) clutter. AP clutter looks and moves like real weather but is an artifact of environmental conditions effecting the radar beam. In addition to clutter removal, thresholding on echo tops removes regions of VIL that are not convective. Regions of level 3 (yellow) and higher are considered an aviation hazard.

To see result of applying an echo tops filter click "Next".

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