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9 Answers

Cloud Heights. AGL or MSL?

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Student Pilot

Can you help clarify when to interpret heights of clouds in weather reports as AGL or MSL? I'm confused by this, and can't get a good handle on any sort of documentation that breaks down VFR minimums, ATIS, metars, TAFs, etc. as being AGL or MSL. 

Thanks in advance.....

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9 Answers

  1. Josh Martin on Aug 08, 2010

    In weather reports, clouds are always given in AGL. So if a METAR says OVC010 then that is overcast at 1,000 feet AGL (VFR minimum). This is beneficial for IFR pilots as you can easily see how low the weather is and what approach is needed with just a glance at the METAR or just a listen to the ATIS/AWOS/ASOS. If it reports a ceiling of 200 then that is right at minimums for most ILS’s. If this were given in MSL it would require a little more thought.

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  2. Bob Weeldreyer on Sep 02, 2010

    In addition to Josh’s information the Area Forecast (FA) plays by a different set of rules. All altitudes in the FA will be in MSL values because of the size of the coverage area as well as the changing elevations. One nice thing about the FA though is that in the precautionary statement it reminds you that non-MSL heights are denoted as CIG or AGL.

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  3. Steven Wilson on Aug 31, 2011

    What does AGL stand for?
    Thank you.

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  4. Paul Tocknell on Aug 31, 2011

    AGL stands for “Above Ground Level”. This is a good way to measure cloud heights and obstacles in reference to the surface.

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  5. Christopher g Ackerley on Oct 20, 2013

    I note that agl is above ground level having trained with Lufthansa. In the 80s the thing that baffles me is why they changed from simple millibar to HP and the one. Thing always bugged me is that tho I know what dew point is they

    Agl is above ground level having said that its not a direct science as the threshold elevation at egccman is 258ft though I think this is taken to account interestingly when we had 24L 06L 24R 06R it was 249ft this is down to the earth magnetic poles strop. Off!! Ex Lh cargo pilot. 80s 727fr@ B787CHRISACk

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  6. Christopher g Ackerley on Oct 20, 2013

    .someone asked me what utc meant it is indeed as obviously universal Time coordination hope this helps @B787CHRISACk

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  7. Mach on Jan 05, 2014

    You know what requires a huge amount of thought because of the way cloud heights are reported? Determining whether a flight can be conducted under VFR. If the airport I’m going to reports OVC025, and there’s a 3,000 ft mountain in front of it, it sounds like the mountain peak will be in the clouds and therefore the flight must be IFR (or I must find a way around the mountain). You must look up the airport’s elevation on the sectional chart to discover if the airport is at an elevation of 2,000 feet, which would put the clouds at 4500 MSL, leaving 1500 feet between the mountain peak and the cloud ceiling, or if it’s at only 800 feet, which would put the mountain top well into the clouds.

    It gets even more laborous when you try to put together a bunch of METAR reports from airports in a mountainous area. You might have a cloud deck at 4,000 feet MSL across the region, but on the METARs it looks like the ceilings are all over the place, and you have to look up each airport individually and add the elevations to the reported ceilings to see the truth.

    But I guess the airlines matter more than VFR pilots, because they have the most money.

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  8. MartyD on Apr 02, 2014

    Does a TAF play by the FA rules or the local reports (METARS)?

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  9. MartyD on Apr 02, 2014

    Cloud Bases? Does a TAF that lists that first base layer play by the FA rules (MSL unless otherwise noted) or by reported weather rules (METARS, say) which are in AGL?

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