User Manual

GPS 500 Pilot’s Guide and Reference
12-21
SECTION 12
ADDITIONAL FEATURES
NEXRAD Intensity
Colors are used to identify the different NEXRAD echo intensities (reectivity) measured in dBZ (decibels of Z).
Reectivity (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 on the 500 Series units using colors
represented by the dBZ values listed in Table 12-6.
Display dBZ Rain
(inches/hour)
Snow
(inches/hour)
Source of NEXRAD Echo
GDL 49 GDL 69
Atmos
Cloud
Rain Snow Sleet Hail
<-10 .00 .00 √
-10 .00 .00 √ √
-5 .00 trace √ √
0 .00 trace - .05 √ √ Very Light
5 .00 trace - .10 √ √ Light
10 0 – trace .10 √ √ Light Light
15 .01 .1-.2 Light Light
20 .02 .2-.3 Light Light
25 .05 .3-.5 Light Light – Medium
30 .09 .4-.7 Light – Moderate Moderate
35 .24 .6-1.0 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 √ √
60 12.7 Extreme √
65 Extreme √
70 Large
75 Large
Table 12-6 NEXRAD Intensity Colors
NOTE: The information presented in this Pilot’s Guide regarding NEXRAD is not meant to be comprehensive.
The NOAA website (www.noaa.gov) contains complete and detailed information regarding NEXRAD weather
radar operation and theory.
190-00181-60 Rev. G