Nexrad Abnormalities; Nexrad Limitations; Nexrad Intensity - Garmin G500 Pilot's Manual

4.10.1

NEXRAD Abnormalities

There are possible abnormalities regarding displayed NEXRAD images. Some,
but not all, causes of abnormal displayed information include:
• Ground Clutter
• Strobes and spurious radar data
• Sun strobes, when the radar antenna points directly at the sun
• Military aircraft deploy metallic dust which can cause alterations in radar scans
• Interference from buildings or mountains, which may cause shadows
• Scheduled maintenance may put a radar off-line
4.10.2

NEXRAD Limitations

Certain limitations exist regarding the NEXRAD radar displays. Some, but
not all, are listed for the user' s awareness:
• The Regional NEXRAD "pixels" are 1.5 minutes (1.5 nautical miles
= 2.78 km) wide by 1 minute (1 nautical miles = 1.852 km) tall. The
CONUS NEXRAD "pixels" are 7.5 minutes (7.5 nautical miles = 13.89
km) wide by 5 minutes (5 nautical miles = 9.26 km) wide. Above 60
degrees of latitude the Regional NEXRAD "pixels" are 3 minutes/nautical
miles. CONUS NEXRAD is not available above 60 degrees of latitude.
The intensity level reflected by the pixel will be the highest level sampled
within the area covered by each pixel.
NOTE: Where it is noted that NOTAM data is available, it is possible only
a subset of the data is available and that more NOTAM reports may arrive
in future updates. Updates occur approximately every ten minutes.
4.10.3

NEXRAD Intensity

Colors are used to identify the different NEXRAD echo intensities (reflectivity)
measured in dBZ (decibels of Z). "Reflectivity" is the amount of transmitted power
returned to the radar receiver. Reflectivity (designated by the letter Z) covers a
wide range of signals (from very weak to very strong). So, a more convenient
number for calculations and comparison, a decibel (or logarithmic) scale (dBZ),
is used. The dBZ values increase as the strength of the signal returned to the
radar increases.
190-00601-02 Rev. J Garmin G500/G600 Pilot's Guide
TOC Cover
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