Defining a ceiling... Uhhh?

[Timbuff10]

I was always taught that a ceiling was defined as the lowest layer of clouds that were broken or overcast. Well, today I actually looked it up and discovered that a ceiling also includes obscuration.

From the FARs:
"Ceiling means the height above the earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as “broken”, “overcast”, or “obscuration”, and not classified as “thin” or “partial”. "

Ok, I learned something new... Then I look in the AIM and find this:
"Obscurations are reported when the sky is partially obscured by a ground-based phenomena by indicating the amount of obscuration as FEW, SCT, BKN followed by three zeros (000). In remarks, the obscuring phenomenon precedes the amount of obscuration and three zeros. "

So anyway, I have seen BKN and OVC on Metars but am I reading this right that if the ceiling exists due to an obscuration, you have to know that FEW @ 000 equals a ceiling or will the metar actually say something like OBS or OBC or whatever the abbreviation is for obscuration?

They way I understand it, technically FEW and SCT could equal a ceiling if they are low enough? That can't be right though or the definition would say so, right?

Seems like Obscurations would be more of a visibility thing rather than a distance between clouds and sfc.

 

[flyguy]

Seems like Obscurations would be more of a visibility thing rather than a distance between clouds and sfc.

Correct - if it is an obscuration that is lowering the ceiling, the ceiling will be reported as the vertical visibility into the obscuration. For example: There is an overcast layer of clouds at 8000 ft, a broken layer at 3000 ft, and the METAR reports VV008. The celiling would be 800 ft, even though the lowest layer of overcast or broken is 3000.

 

[Timbuff10]

Yeah, it just seems weird though... When you are in the cloud then we should refer to it as visibility and if you are not in the cloud then the talk should be how far away it is.

I think this is one of those things that I somewhat learned as a private pilot and then never really looked back at it through the rest of the ratings even though there was so much more to it.

 

[dakovich]

Yeah, it just seems weird though... When you are in the cloud then we should refer to it as visibility and if you are not in the cloud then the talk should be how far away it is

yup. obscuration basically being anything blocking or obstructing our view upward toward the sky. so, any surface based obscuration/obstruction (ie. fog), will be defined by VV or visibility. fog being a ground based cloud. if the obscuration happens to be a cloud above the surface then we just list the concentration of that obstruction...broken/overcast....and we also list how far above the ground that obscuration/obstruction is above the ground.

 

[Mavmb]

Scattered and few are not for determining if you need an alternate. Only a broken or overcast layer requires an alternate when using the 1,2,3 rule.