Visibility is considered unrestricted if greater than 6 miles???

"Ben Hallert" wrote in message
oups.com...

It's not a conspiracy of mediocrity, it's due to a technical limitation
of the scatterometer technology used by ASOS's to determine visibility,
if I recall correctly. They can only really be accurate out to about 6
miles. A human with a Mark I Eyeball could pick a landmark furthre
away and provide a bigger distance, but for all intents and purposes,
the max visibility will be defined by the technical limitations of the
available data sources.

Of course, I might be dramatically incorrect, this was what I learned
from my instructor.


ASOS reports visibility up to ten miles.

"Jose" wrote in message
. com...

Then visibility should be reported as "greater than six" (which I have
heard)


You've heard "greater than six" or "greater than" reported? ASOS reports
visibility up to ten miles.

"John Gaquin" wrote in message
...

When I learned to fly in the Denver area, I got accustomed to wx reports
that included "clear and 70". The guys in the tower at Stapleton would
just look south. If they could see Pike's Peak, the vis was 70. Easy.
Infallible. No gizmo to break.


Being able to see an object 70 miles away does not mean the visibility is 70
miles. Prevailing visibility is what is reported, that's the greatest
distance that can be seen throughout at least half the horizon circle, not
necessarily continuous. If Pike's Peak could be seen but the furthest
object to the north west or east that could be seen is five miles away then
prevailing visibility is five miles, not 70.

John Gaquin wrote:

"Icebound" wrote in message

Now, in general, when you had manned systems, airports attempted to have
visibility markers out to *at least* 15 statute miles, and a report of 15
was the norm for "unrestricted" visibility.


When I learned to fly in the Denver area, I got accustomed to wx reports
that included "clear and 70". The guys in the tower at Stapleton would just
look south. If they could see Pike's Peak, the vis was 70. Easy.
Infallible. No gizmo to break.

Exactly, that's what we do here. We have five mountain ranges in view,
the closest being about 35 miles away and the farthest about 90. I
never realized how bad 10 mile visibility was until I had to fly in it
once when some forest fires in the western part of the state filled the
air with smoke. 100+ mile vis is standard here.

"B A R R Y" wrote in message
...

I've seen both in the same geographical area.

I always thought it depended upon the specific local equipment.


The Federal Meteorological Handbook indicates that 10 miles is the highest
reported value for automated systems. It also states that some automated
stations may not report the reportable visibility values of 6, 8, and 9
miles. See Table 12-1.

http://www.ofcm.gov/fmh-1/pdf/L-CH12.pdf

"Steven P. McNicoll" wrote in message
link.net...

"John Gaquin" wrote in message
...

When I learned to fly in the Denver area, I got accustomed to wx reports
that included "clear and 70". The guys in the tower at Stapleton would
just look south. If they could see Pike's Peak, the vis was 70. Easy.
Infallible. No gizmo to break.


Being able to see an object 70 miles away does not mean the visibility is
70
miles. Prevailing visibility is what is reported, that's the greatest
distance that can be seen throughout at least half the horizon circle, not
necessarily continuous. If Pike's Peak could be seen but the furthest
object to the north west or east that could be seen is five miles away
then prevailing visibility is five miles, not 70.

The reports were "clear and 70". The reporting basis as related to me by
the tower people at Stapleton was as I recounted above. I was there. If
you feel the need, forward your post to the Stapleton tower staff on duty in
1970.

"Newps" wrote in message
...
When I learned to fly in the Denver area, I got accustomed to wx reports
that included "clear and 70". The guys in the tower at Stapleton would
just look south. If they could see Pike's Peak, the vis was 70. Easy.
Infallible. No gizmo to break.

Exactly, that's what we do here. We have five mountain ranges in view,
the closest being about 35 miles away and the farthest about 90. I never
realized how bad 10 mile visibility was until I had to fly in it once when
some forest fires in the western part of the state filled the air with
smoke. 100+ mile vis is standard here.

And how far can you see at altitude? ;~)

(Something east coasters don't get to enjoy too much?)

"John Gaquin" wrote in message
. ..

The reports were "clear and 70".


I didn't dispute that.



The reporting basis as related to me by
the tower people at Stapleton was as I recounted above.


Well, now you know they were doing it incorrectly.



I was there.


Good for you.



If you feel the need, forward your post to the Stapleton tower staff on
duty
in 1970.


I don't feel that need, even if it was possible.

Just out of curiosity, why did you feel the need to be a dickhead?