The display is an image representation of the Nexrad radar reflectivity
overlayed with cloud tops and centroid movement. The Nexrad Radar Coded
Message (RCM) product originates as an automated text message generated
at each NWS radar site and transmitted over the AFOS communications
network. The RCM reflectivity data has spatial resolution of about 12 km
and is updated every 30 minutes. The RCM was intended as a replacement
for the Manually Digitized Radar (MDR) product which has been used for
years as the input to the NWS Radar Summary graphic available over fax
and other circuits. The raw RCM has considerable false echoes, so it is
hourly by the Aviation Weather Center (AWC) before being formatted as an
MDR in the autoROB product transmitted over AFOS. The autoROB is now
used as the input for the NWS Radar Summary chart. The editing of the
RCM at the AWC is an automated process that checks the RCM for
meteorological validity when compared to current satellite images,
synoptic conditions, neighboring radar sites, and lightning.
The displayed image is the edited reflectivity. The RCM includes the max
top for each radar's area of coverage. The other tops shown on the
display are derived from the satellite images at the centers of
convective activity. Movements shown are the radar centroid movements as
generated by the Nexrad processor.
The images are updated twice hourly and are posted at HH:15 and HH:45.