Visibility is considered unrestricted if greater than 6 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.

"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.

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.

"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?)

"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.

"Peter R." wrote in message
...

Flying from Buffalo, NY, to Reading, PA, this afternoon, I call up
Cleveland Flight Watch to report a weather pirep.

"Visibility is restricted in haze to about one five miles," I include.

"45 Whisky," the voice responds, "visibility is considered unrestricted if
it is greater than six miles so I am going to put unrestricted."

"Huh?" I let slip out, "Really?"

"Yes, really," he answers.

If this is indeed true, I have been doing it wrong for almost 1,000 hours
now. Too late tonight for me to go digging through the AIM, but is this
really true?

Imagine being VFR through typical New England haze of 7 miles and being
told by Fligh****ch that pireps all over the region are reporting
unrestricted visibility.

That just doesn't seem right.


It isn't right. Perhaps you misunderstood him or perhaps he didn't explain
it well. If visibility is 7 miles or more the restriction to visibility is
not included in the report. If haze is reducing the visibility to 6 miles,
for example, the visibility is reported as 6 miles in haze If haze is
reducing the visibility to 7 miles the visibility is reported as 7 miles
with no mention of what is limiting visibility..