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

[Peter R.]

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.

--
Peter

[Jose]

> Imagine being VFR through typical New England haze of 7 miles

Now imagine the same thing in SoCal, which is where I learned to fly. I
think they have several definitions of "three miles", depending on the
day. :)

Jose
--
The price of freedom is... well... freedom.
for Email, make the obvious change in the address.

[Ben Hallert]

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.

Ben Hallert
PP-ASEL

[Jose]

> 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.

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

Jose
--
The price of freedom is... well... freedom.
for Email, make the obvious change in the address.

[Peter R.]

Ben Hallert > wrote:

<snip>
> 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.

Since the source of a pirep is a pilot, not an automated weather station,
and the main recipient of a pirep is a pilot, not an automated weather
station, visibility should be reported as an estimation in the pilot's
opinion much greater than that which is artificially restricted by
automation.

In any event, I did call Buffalo FSS late last night to ask the specialist
about this and in his opinion the Cleveland specialist was incorrect.
Report visibility in the distance we see, were his words.

Again, had I been a low time VFR pilot launching on a cross country, I
certainly would want to know about haze limiting visibility, for even 10
miles and haze will appear much lower as the sun draws closer to the
horizon.

--
Peter

[Roy Smith]

Peter R. > wrote:
>Again, had I been a low time VFR pilot launching on a cross country, I
>certainly would want to know about haze limiting visibility, for even 10
>miles and haze will appear much lower as the sun draws closer to the
>horizon.

This P6SM stuff is one of the (few) ways the ICAO weather reporting
system of TAF and METAR is inferior to our old SA/FA system. The old
FAs used to forecast visibility as 10, 15, 20, whatever was
appropriate. Now all that just gets folded into P6SM. For somebody
planning a VFR X/C (especially a student or inexperienced pilot),
there's a big difference between 6 miles and 20 (or even 10).

It's not like the computer models can't differentiate between them.
It doesn't even take any more characters to transmit. It's just plain
dumb that the information exists and is kept hidden.

[Icebound]

"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.

The short answer to the OP question is: YES!

This is not so much due to a "technical limitation", as it is due to
*history*.

The requirements forever (well, at least since the 1950's), have been that
.... no restriction to visibility is reported, whenever the visibility is
more than 6 statute miles... In other words, an observation may *not* read
7 miles in haze, or 7 miles in mist, etc. *Precipitation* may be reported
at visibilities greater than 6, but you do not report
non-precipitation-phenomena by itself. You would just report "visibility 7
statute miles", period.

Thus, a visibility above 6 statute miles, as per the technical requirement
of observing weather, is "not obstructed".

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. Thus, you kind of knew that
something was going on, should that station suddenly report "10", or "8",
even if he did *not* show the reason.

However, with the increasing advent of automated systems, you have lost that
extra human insight, because the technical requirement is met by saying....
"greater than 6" equals "not obstructed"..... so you might get "greater than
6" on a day when visibility is 50, and from the same station you get
"greater than 6", when visibility is 7.

In that sense, I *DO* say that it *is* a conspiracy of mediocrity. To
automate things, and to meet only the basic requirements of producing a
METAR... a lot of the stringent reporting practices of the 60's and 70's
seem to be slipping away.

[Peter R.]

Icebound > wrote:

> In that sense, I *DO* say that it *is* a conspiracy of mediocrity. To
> automate things, and to meet only the basic requirements of producing a
> METAR... a lot of the stringent reporting practices of the 60's and 70's
> seem to be slipping away.

Thanks, Ice. I appreciate your knowledgeable weather contributions to this
group.

--
Peter

[John Gaquin]

"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.

[Steven P. McNicoll]

"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..

[Steven P. McNicoll]

"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.

[Steven P. McNicoll]

"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.

[Steven P. McNicoll]

"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.

[Newps]

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.

[Steven P. McNicoll]

"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

[John Gaquin]

"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.

[Matt Barrow]

"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?)

[Steven P. McNicoll]

"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?