To display the NEXRAD Intensity Legend:
1.
While viewing the XM Weather page, press the
MENU key to display the Page Menu.
Turn the large or small knob to select "Display
2.
legend?"
Press ENT to display the NEXRAD Intensity
3.
Legend.
4.
Turn the large or small knob to scroll through
the full table. Press CLR to return to the normal
view.
NEXRAD Abnormalities
There are possible abnormalities regarding dis-
played 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
NEXRAD Limitations
Certain limitations exist regarding the NEXRAD
radar displays. Some, but not all, are listed for the
user' s awareness:
• NEXRAD base reflectivity does not provide suf-
ficient information to determine cloud layers or
precipitation characteristics (hail vs. rain, etc).
• NEXRAD base reflectivity is sampled at the
minimum antenna elevation angle. An indi-
vidual NEXRAD site cannot depict high altitude
storms at close ranges, and has no information
about storms directly over the site.
• Neither NEXRAD weather data nor the age of
the NEXRAD weather data are displayed at a
zoom range of less than 10 NM. The resolu-
tion of displayed NEXRAD data is 2 kilometers.
Therefore, when zoomed in on the display,
each square block is 2 kilometers. The intensity
level reflected by the square will be the high-
est level sampled within the 2 kilometer square
area.
XM Weather METARs
XM Weather METARs (Meteorological Aerodrome
Reports) are available on the XM Weather page. When
enabled (that is, when "METAR" is shown in the upper
left corner of the page), airports with METAR infor-
mation above a certain severity level are marked with
colored flags on the display. Refer to the XM Weather
legend for a description of the color code. The update
rate is every 12 minutes.
190-00356-30 Rev C
Part Two: Section 2
XM Weather
15
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