GDL-49 and Levels of Radar Returns

"O. Sami Saydjari" wrote in message
...
In googling around a bit, I found the following:

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At: http://www.weatherzone.com.au/misc/g...y.jsp?letter=V

"Video Integrator and Processor, which contours radar reflectivity (in
dBZ) into six VIP levels:
• VIP 1 (Level 1, 18-30 dBZ) - Light precipitation
• VIP 2 (Level 2, 30-38 dBZ) - Light to moderate rain.
• VIP 3 (Level 3, 38-44 dBZ) - Moderate to heavy rain.
• VIP 4 (Level 4, 44-50 dBZ) - Heavy rain
• VIP 5 (Level 5, 50-57 dBZ) - Very heavy rain; hail possible.
• VIP 6 (Level 6, 57 dBZ) - Very heavy rain and hail; large hail
possible."

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At:
http://www.garmin.com/manuals/773_Ga...deAddendum.pdf

Ok, now, from the Nextrad intensity table on page 13 of the Garmin
"400/500 Series garmin Options Displays", I learned:

GREEN means 5-30 dBZ
YELLOW means 30-55 dBZ
RED means 55-75 dBZ

So...
Green is VIP Level 1
Yellow is VIP Levels 2,3,4
Red is VIP levels 5 and 6


Don't draw this conclusion unless you know exactly what the standards Garmin
is using and what the radar system is using and whether they are compatible
with the VIP levels that you are using. Nexrad seems to use different
scales depending of what mode it is in and additionally, there are at least
2 VIP scales (maybe more), one that has six levels and one that has 15
levels. It also seem to produce different dbz readings than an airborn
radar. There was a major airline accident in the SE (Georgia I think) where
an airliner flew into a 50+ dbz echo (on an airborn radar) and the airliner
was virtually destroyed by hail (the engines where broken up internally. I
doubt that this is what Garmin is displaying as a borderline yellow/red
echo. There is a good chance that you will not survive flying into a VIP 4
storm.

Mike
MU-2

"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?


By the way, when you flew through the "just level 4 stuff", how did you find the ride?

--
Cheers,
John Clonts
Temple, Texas
N7NZ

Surprisingly, the most I experienced was light turbulence. The landing
was uneventful. At the same time, I expect I was pretty lucky and
probably will actively avoid landing in these sorts of conditions in the
future.

My NEXTRAD showed "green" so I was unconcerned going in. It was only
from approach that I started hearing about level 4 and leve 5 stuff
around the airport. Had I known, I would have diverted north.

-Sami
N2057M, Piper Turbo Arrow III


John Clonts wrote:
"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?



By the way, when you flew through the "just level 4 stuff", how did you find the ride?

O. Sami Saydjari wrote:

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.

That's pretty funny because even the airlines ain't flying thru a level
four return on final.

Newps wrote:



O. Sami Saydjari wrote:

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.


That's pretty funny because even the airlines ain't flying thru a level
four return on final.


That is pretty odd. I am sure she said level 4. The rain seemed only
moderate to me and visibility seemed like it was 2-3 miles. Perhaps I
got lucky. How sure are you that airlines do not land in level 4? If
so, it seems that they would advise a light aircraft to divert or hold.

"O. Sami Saydjari" wrote:



That is pretty odd. I am sure she said level 4. The rain seemed only
moderate to me and visibility seemed like it was 2-3 miles. Perhaps I
got lucky. How sure are you that airlines do not land in level 4? If
so, it seems that they would advise a light aircraft to divert or hold.

ATC does not provide advice as to whether you should divert or hold because
of thunderstorms in the area.

"O. Sami Saydjari" wrote in message
...


Newps wrote:



O. Sami Saydjari wrote:

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.


That's pretty funny because even the airlines ain't flying thru a level
four return on final.


That is pretty odd. I am sure she said level 4. The rain seemed only
moderate to me and visibility seemed like it was 2-3 miles. Perhaps I got
lucky. How sure are you that airlines do not land in level 4? If so, it
seems that they would advise a light aircraft to divert or hold.

The approach controller may have been using the 15 level VIP scale where
level 4 is not severe. If you fly into the type of level 4 that Newps is
talking about, you might (probably) won't come the other side. The airport
would probably shut down with a "real" level 5 thunderstorm in the near
vicinity

Mike
MU-2

The approach controller may have been using the 15 level VIP scale where
level 4 is not severe. If you fly into the type of level 4 that Newps
is talking about, you might (probably) won't come the other side. The
airport would probably shut down with a "real" level 5 thunderstorm in
the near vicinity


What question would one ask to ascertain if it's "four out of 15" or
"four out of six"?

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.

"Jose" wrote in message
...

The approach controller may have been using the 15 level VIP scale where
level 4 is not severe. If you fly into the type of level 4 that Newps is
talking about, you might (probably) won't come the other side. The
airport would probably shut down with a "real" level 5 thunderstorm in the
near vicinity


What question would one ask to ascertain if it's "four out of 15" or "four
out of six"?

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.


He may not know know the answer but you could always ask: "Has anybody
successfully come out the other side?" :-)

As a practical matter he is going to start covering his rear on tape if it
looks like anyone is venturing into a level four (out of six) thunderstorm.
"Say intentions", "how many souls on board", "do you have airborn radar" are
all clues not to go in.

A level four is considered a "strong" thunderstorm, one step below "severe"
thunderstorms with large hail, very high winds and tornados.

Mike
MU-2

Newps wrote:

O. Sami Saydjari wrote:

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.

That's pretty funny because even the airlines ain't flying thru a level
four return on final.

Well, Eastern did at JFK in 1976 (OTA) and Delta did at DFW in 1985 (OTA).