Garmin GDU™ 37X Pilot’s Guide 190-01054-00 Rev. E106Hazard AvoidanceOverviewGPS NavigationFlight PlanningHazard AvoidanceAdditional FeaturesAppendicesIndexComposite data from all the NEXRAD radar sites in the United States is shown. Thisdata is composed of the maximum reflectivity from the individual radar sweeps. Thedisplay of the information is color-coded to indicate the weather severity level.The display of radar coverage is always active when NEXRAD is selected. Areaswhere NEXRAD radar coverage is not currently available or is not being collected areindicated in grayish-purple (Weather (WX) Page Only). Radar capability exists in theseareas, but it is not active or is off-line.neXraD abnorMalitiesThere are possible abnormalities regarding displayed NEXRAD images. Some, butnot all, of those include:• Ground clutter• Strobes and spurious radar data• Sun strobes, when the radar antenna points directly at the sun• Military aircraft deploy metallic dust (chaff) which can cause alterations in radarscans• Interference from buildings or mountains, which may cause shadowsneXraD liMitationsCertain limitations exist regarding the NEXRAD radar displays. Some, but not all, arelisted for the user’s awareness:• NEXRAD base reflectivity does not provide sufficient information to determinecloud layers or precipitation characteristics (hail vs. rain). For example, it is notpossible to distinguish between wet snow, wet hail, and rain.• NEXRAD base reflectivity is sampled at the minimum antenna elevation angle. Anindividual NEXRAD site cannot depict high altitude storms at close ranges, andhas no information about storms directly over the site.• Radar coverage only extends to 55°N.• Any precipitation displayed between 52°N and 55°N is unknown.
