Solved fog model inconsistency
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@suhkoi69 said in fog model inconsistency:
@jayb said in fog model inconsistency:
So are you saying that in this case shown here, with LSOs barely being able to see the stern, a jet up high looking down will be able to see the carrier clear as day ?
According to my understanding, we need to know 2 criteria longitudinal visibilty and fog altitude …if the altitude fog is lower than the longitudinal visibility , then you are right , a jet up high looking down will be able to see the carrier clear as day
So, shallow (low altitude but perhaps widespread) fog can be see-through from a distance and/or up high. Not sure if this is a BMS construct or a real-life feature, although Mav-jp hinted to it being a thing in real-life.
A thick layer of fog (up to a high altitude) on the other hand should not be see-through from any vantage point, right ?
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@jayb said in fog model inconsistency:
@Mav-jp So are you saying that in this case shown here, with LSOs barely being able to see the stern, a jet up high looking down will be able to see the carrier clear as day ?
I get that the in-the-fog perspective is different from the above-the-fog perspective, but still.
it just depends on the fog depth
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@jayb said in fog model inconsistency:
A thick layer of fog (up to a high altitude) on the other hand should not be see-through from any vantage point, right ?
Right! If the vertical layer of the fog is thick enough, you should not be able to see the ground.
On the other hand, if the vertical layer is thin (like MIFG on METAR), you will be able to see the ground direct bellow you.I fly very often and this really happens
Greetings from Brazil!
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@luke777
yes, MIFG translates into mist / fog, meaning fog surrounded by mist or FG meaning fog surrounded by clear air. -
@Gustav_Guns said in fog model inconsistency:
meaning fog surrounded by clear air.
Yep, i remember a day when the airport was closed for VFR operations due to MIFG, but when i look up, the sky was CRYSTAL CLEAR and BLUE AS WATER!
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@Gustav_Guns said in fog model inconsistency:
@luke777
yes, MIFG translates into mist / fog, meaning fog surrounded by mist or FG meaning fog surrounded by clear air.MIFG means shallow fog (MI from the French word “mince”, which means thin; FG from FG)
Mist would be BR (again from a French word, “brume”)The official difference according ICAO is in the visibility:
Mist (BR) is used when visibility > 1km
Fog (FG) is used when visibility < 1km
Both BR and FG happen because of the presence of water droplets in the air, unlike haze - abbreviated as HZ - which happens when there are pollutants in the air (e.g. dust particles) -
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To @suhkoi69’s original pics. Yes, sometimes, but not always does it always looking like a layer. A bad and high mist (BR)/Haze(HZ)/less limiting fog(FG) can have the effect you are seeing, especially a warm front with its typical precipitation fog. The layers you seem to be talking about that block the view of the ground is usually radation fog that will pool in lower elevation areas locally under low level temperature inversions with low winds. These can look like clouds from above that will happen to be filling in these areas.
Yes it’s completely possible to have changes in visibility as @Seifer diagrams and @Mav-jp describe with an on top view (flight visibility). We teach civilian pilots that instrument approach minimums are actually flight visibility numbers and sometimes you may want to shoot the approach even if the ASOS/AWOS/ATIS is calling close but less that legal minimums because that visibility is ground visibility, you may actually be able to see down through it. But if that is the case, file a PIREP to both CYA and let others know flight visibility is better than the reported ground.
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This is a great visual of fog if you don’t mind the Instagram link. You can see a little of each of the things we are discussing here if you scroll through all of them: the coverage of low elevation with “islands of ground” with higher elevation, forward visibility through fog, and a mix of visibilities above the fog.
https://www.instagram.com/p/C0-e70eReF3/?igshid=MzRlODBiNWFlZA==
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Wait U4 for more information on this…
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@Snake122 Those are some great visuals. Although it seems like the only ground objects visible are the ones protruding through and above the fog layer. The low ground seems to be fully obscured by the fog even when viewed from above
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@jayb depends on the fog, your position, etc. Scroll through on the forth one that’s a still and watch the takeoff video towards the end where you can see the forward visibility continues to be a little more than expected instead of just hitting the fog not seeing anything forward. But this is more the radiation temperature inversions sea of fog than the wide spread warm front style precipitation fog that can be similar to close range wall of haze that BMS has.
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A test one could do in BMS is get on top of a layer of fog that allows you to see the ground from above, get down low inside of it and check if you can see the sky directly above you.
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@Snake122 Yeah, fog is not just fog, it can be very different. Different density, different elevation. So I suppose that sometimes it can be see-through from above, other times fog is too dense even for that slant view. Makes me wonder what determines how dense fog becomes. Ground vs air temp, local elevations perhaps