Nexrad Limitations; Xm Weather Metars - Garmin GNC 420AW Pilot's Manual

Part Two: Section 2
XM Weather
XM Weather Label and NEXRAD Source
U.S.
XM Weather Label and NEXRAD Source
Canada
NOTE: The only weather product available for Canada
is Canadian NEXRAD.
16

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 H