U.S. METAR Visibility incorrect at most airports

New in SU7 - Steam build

Many U.S. airports use visibility ‘10sm’ to mean Greater than 10, or unlimited.

Since haze has been corrected in FS as of this build, and this 10sm is being handled as a real value, haze is being depicted even when the real airport is unlimited vis.

Please consider logic in the sim to treat 10sm as Unlimited at U.S. airports. And values less than 10 as real values.

The problem with real METARS is that 10SM could mean “unlimited” or it could mean that the visibility is indeed exactly 10 miles - and 10 miles at the surface can be considerably less in flight.

I have done plenty of r/w flights here in the northeastern US on hot, humid summer days when the METAR at the airport is 10, and the inflight visibility is probably closer to 5. On the other hand, in fall or winter - especially after the passage of a cold front followed by a high pressure Canadian airmass, a 10SM METAR could easily equate to 70+ miles or more.


I understand that, but since the metar will consider 10 as strictly 10, it will be wrong more often than it is right in the current set up.

Since we have no way of knowing if 10 means 10, or if it means Unlimited, then it would be more frequently correct to assume unlimited. Otherwise every (or nearly every) U.S. field is going to have haze permanently.


Yeah this is a problem a fairly big US problem. I did a flight out of KOMA where I live tonight where the skies were clear blue in real life and there was a layer of haze on the ground with 10SM (meaning in the U.S. typically 10 miles+ or clear) on the metar.

Is that what it’s doing? Because it doesn’t seem like it at times for me. I’ve noted airports where the visibility is well below 10 while the METAR reports 10.

I’m not sure what it’s doing to be honest. My guess is the new “humidity” slider in the weather settings is directly tied to reported relative humidity and this produces haze/mist that only roughly coincides with visibility at the airport.

I’m 2 miles from the runway here and the METAR is reporting greater than 10 and I can’t see it. The sim isn’t just locking the visibility at something like 10, at least not always.

Hopefully they will use temperature/dewpoint spread from the METAR to determine relative humidity, which might help refine it. Of course, there can be significant haze in the absence of high humidity if the source is dust or air pollution. This new system will undoubtedly go through further development.

Could be.

All I know is that the effect looks great, but its being applied inappropriately and making a rather pleasant day look like muck.

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It’s making VFR flying dangerous actually. A couple of my flights were definitely IMC even though the METAR was 10SM.

PHLI was 10SM on the METAR and visually unlimited in the sim at and near the field, but a mile over it was way less than 10SM. I haven’t found rhyme or reason to it yet.

It sure does


I noticed it immediately after takeoff. This is on Series X. I took off near my house and saw a layer of mist/haze. Looked outside and it’s clear. I think it reads the METAR as visibility set to 10 miles. And can’t decide if it’s 10 or unlimited, so it produces a haze over the entire ground.

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Yeah I’m seeing the same thing.

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Guys, if you agree… VOTE

Only happens in U.S. airports?

I tried a few European airports but it appears Zurich, Paris are IRL socked in with fog. The other 2 I tried were Frankfurt and Nice and they looked suspiciously similar… metars show low cloud decks at Frankfurt and 6 miles visibility at Nice with no mention of fog or clouds. Inconclusive until the weather changes. but it looks like to me in Europe there are problems as well.

The haze is too excessive. I took off from Cabo San Lucas, Mexico earlier this afternoon and saw this:

At the time, the METAR for MMSL was showing 10SM visibility:

MMSL 182140Z 20008KT 10SM SKC 30/10 A2998

For an airport near the ocean in mid-late afternoon, it makes no sense to see a haze layer over land but not over the ocean. If anything, it would be the other way around.


The “10 SM in METAR = 10 SM in sim” bug was introduced in FS2000 and was fixed in FS2002. Seems we have a regression 20 years later.

Solution, same as always: Asobo team leaders need to provide better guidance to their developers. How METARs work is not new information – if you already know it.

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In all fairness tho, METARS also aren’t a great weather source… They are local conditions at the airport and are only valid for as far as the observer can see.

In order to get really accurate ‘weather’ (rather than ‘local conditions’) they’d need to average the Metar against the larger scale data from Meteoblue and sort out what the big picture really is. But if you have a METAR that says ‘x’, and you know the weather in the area is ‘y, z, w,’ its pretty easy to figure out why the Vis is 10, or if it might be actually unlimited.

Thats what they need to bake into the engine… Does 10sm sound real based on pressure and humidity and so on? Or is it 95F and 9% humidity and 30.05 altimeter (in which case its almost certainly unlimited).


Yeah I agree, at least with the first half of your post. That is why I have been saying all along that using METARs as a weather input is a bad idea, they should stick with their weather modeling and improve that instead. Looking at Meteoblue’s weather products at their webpage the necessary data is already there. Just use the visibility from the models to drive the visibility in the sim.

As for estimating visibility based on pressure and humidity, that does not work. That approach overlooks visibility restrictions due to haze, dust, smoke, and maritime aerosols, which in large parts of the world are the dominating visibility impairments most of the time.

Haze, smoke etc have encodings that should appear in the Metar if they are present, just like snow, etc.

Can’t speak to maritime aerosols, but there are lots of informational codes that can pop up in there and as long as they are properly interpreted by the sim, it’d work just fine.

In principle yes, but I think this part is the problem:

It is too complicated to try to implement a mechanism to properly interpret METARs to derive data that is not actually in the METARs, i.e., try to estimate actual visibility from a METAR that only has a lower limit on visibility. It is a fundamentally hard problem. With the limited resources that can be put into solving it I have little hope a good solution will be obtained.

Much better in my view to rely on Meteoblue weather data. That way we can leverage work done for other weather data consumers, which means more resources are available to address it.

I have had to deal with providing time-accurate nowcast or aftercast visibility data for specific locations professionally in a previous job, based on data similar to METAR data. It is a very complex thing to do, and we spent an awful lot of effort on it with rather unsatisfactory results. I do not think it is realistic for a flightsim to try to implement something like that on top of everything else it needs to do.

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