Rod Machado's column in the latest AOPA Pilot covers the subject very well.

Gerry

"O. Sami Saydjari" wrote in message
...
As I was coming into Grand Rapids (KGRR) yesterday, the controller
announced that there was a "level 5" return (or perhaps she said "cell")
on final to runway 8, so I was vectored to 35 where there were mostly
"just level 4" stuff. So, forgive my ignorance, but where are these
levels defined? I assume they have to do with what sort of radar return
they get off a cloud and therefore has to do with rain intensity. Does a
level 5 return imply that a thunderstorm is likely to be generating it?

Also, I have a GDL-49 Satellite Data Link Transceiver linked to my Garmin
430 display. I understand (and now have seen) that these things just are
not adequate to locate big cells. Rather, they show large areas of
showers. Are these based on satellite imagery, or from aggregated ground
station data or what?

Also, how to the radar levels (1 thru 6?) relate to the colors shown on a
GDL-49 display on a Garmin 430? Does red equal level 5 or level 6? I
think only have red, yellow and green...so it seems there are not enough
colors to show 6 levels.

-Sami, N2057M, Piper Turbo Arrow III