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Value Added Service Weather Products
VALUE ADDED SERVICE WEATHER PRODUCTS
The following is a discussion of weather products offered with the value
added VDL subscription service. Accessing and navigating these ser-
vices will be discussed in detail later in this section.
All basic and value-added products (except those identified as VDL only)
can also be obtained through a single fee-based XM subscription ser-
vice.
NEXRAD
Next Generation Radar (NEXRAD) is formally designated WSR-88D,
which stands for Weather Service Radar (Doppler) and was commis-
sioned in 1988.
FIS VDL provides NEXRAD base reflectivity and XM WX provides
NEXRAD composite reflectivity. Each NEXRAD ground radar site scan
is composed of separate beam scans at several elevation angles for
360 degrees around the site. Base reflectivity is the highest precipita-
tion echo (reflectivity) contained in the lowest NEXRAD radar elevation
angle scan (5 degrees). Composite reflectivity provides the highest
precipitation echoes within all of the elevation scan angles. The
NEXRAD base or composite reflectivity modes provide a display of
echo intensity depicted by colors. NEXRAD information is good for
identifying precipitation intensity.
This NEXRAD base reflectivity data product content consists of reflec-
tivity measured at the minimum scan angle of 0.5 degree elevation.
CAUTION: NEXRAD data must be used for strategic planning pur-
poses only. Due to inherent delays and relative age of the data
that can be experienced, NEXRAD data cannot be used for tactical
avoidance of weather.
NEXRAD reflectivity images
older than 75 minutes are dis-
carded and no longer dis-
played.
Figure 2-1 shows a typical
NEXRAD display. Political
boundaries, rivers, lakes, and
oceans are depicted in con-
junction with weather.
The display range may be
Figure 2-1
changed to zoom in on a spe-
cific area to get a more detailed weather picture, or zoom out to display
a wider range.
2-13
Rev 4 Aug/2007
KMD 250 Pilot's Guide
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