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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
To see result of applying an echo tops filter