Garmin GXM 30A - Manual (Page 38)

3 GXM 30A XM Radio Smart Antenna Owner’s Manual
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NEXRAD Intensity
Colors are used to identify the different
NEXRAD echo intensities (reflectivity)
measured in dBZ. (decibels of Z).
“Reflectivity” (designated by the letter Z) is
the amount of transmitted power returned to
the radar receiver. The dBZ values increase
as returned signal strength increases.
Precipitation intensity is displayed using
colors represented by the dBZ values listed
in the table to the right.
Display
Rain
Display
Snow
dBZ
Rain
(inches/hour)
Snow
(inches/hour)
Remarks
Rain Snow
<-10 .00” .00”
-10 .00” .00”
-5 .00” trace
0 .00” trace - .05” Very Light
5 .00” trace - .10” Light
10 0” - trace .01” Light Light
15 .01” .1 - .2” Light Light
20 .02” .2 - .3” Light Light
25 .05” .3 - .5” Light Light - Moderate
30 .09” .5 - .7” Light - Moderate Moderate
35 .24” .7 - 1.0” Moderate Heavy
40 .48” 1” + or sleet Heavy Heavy
45 1.25” 1” + or sleet Heavy Heavy
50 2.5” sleet Intense
55 5.7” sleet Extreme
55+ 12.7” Extreme
The information presented in this manual is not
meant to be comprehensive. The NOAA web
site contains complete and detailed information
regarding NEXRAD weather radar operation
and theory. You can visit them at
www.noaa.gov.