Live Weather pressure does not match METAR at high altitude airport

[DementedCorn327]

ISSUE DESCRIPTION

Description of the issue:
Pressure in METAR is different than the one injected into the sim and difference seems larger based on the airport altitude

EDIT: others values coming from the METAR (temperature/wind/visibility) should also be checked since discrepancies can also be observed comparing information coming in the weather debug windows vs METAR.

Provide specific location or coordinates: see below the 4 airport picked-up as example based on their altitude

Provide time and date of the observed weather issue:

[PC Only] Did you remove all your community mods/add-ons? If yes, are you still experiencing the issue? yes

FREQUENCY OF ISSUE

How often does this occur for you (Example: Just once, every time on sim load, intermittently)? every time

REPRODUCTION STEPS

Please list clear steps you took in order to help our test team reproduce the same issue:

1. spawn at different airports with different altitudes, Live Weather enabled
2. compare the indicated pressure in the aircraft avionics with the pressure reported in the METAR, they don’t match (neither with past METAR pressure).

• KJFK (12 ft): Metar=30.05, sim=30.09. Difference = +0.04 in
• KDEN (5366 ft): Metar=30.11, sim=29.88. Difference = -0.23 in
• MMMX (7293 ft): Metar=30.39, sim=29.94. Difference = -0.45 in
• SLLP (13215 ft): Metar=30.65, sim=30.21. Difference= -0.44 in

YOUR SETTINGS

If the issue still occurs with no mods and add-ons, please continue to report your issue. If not, please move this post to the User Support Hub.

What peripherals are you using, if relevant:

[PC Only] Are you using Developer Mode or have you made any changes to it?

[PC, MSFS 2020 Only] Are you using DX11 or DX12?

[PC Only] What GPU (Graphics Card) do you use?

[PC Only] What other relevant PC specs can you share?

MEDIA

KJFK, difference = +0.04 in:

KDEN, difference = -0.23 in

MMMX, difference = -0.45 in

SLLP, difference= -0.44 in

[END OF FIRST USER REPORT]

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For anyone who wants to contribute on this issue, Click on the button below to use this template:

Do you have the same issue if you follow the OP’s steps to reproduce it?
•

Provide extra information to complete the original description of the issue:
•

If relevant, provide additional screenshots/video:
•

[CharlieFox00]

Interesting. The ratio is different for all four, so not sure what’s making it in there. There are other background calculations that account for ambient pressure, density altitude, etc, but none of those should push back to the altimeter setting. Maybe one of those things accidentally got let loose to feed back, or perhaps something else on the ingest is fouling the data?

Nice find!

[DementedCorn327]

Another test at MMMX, this time comparing pressure/temperature/visibility that come from the METAR, none of the values match with what comes in the weather debug window:

Metar pressure = 30.30 in, in sim = 30.00 in
Metar temperature = 21 C, in sim = 16.5 C
Metar visibility = 5.21 NM (9260 m), in sim = 15500 m

If a discrepancy is confirmed for pressure it could go beyond than just that value but also applies to the others values coming from the Metar (temperature/visibility/wind).

[Downscc]

Do you have the same issue if you follow the OP’s steps to reproduce it?
•

Provide extra information to complete the original description of the issue:
•

If relevant, provide additional screenshots/video:
• I had the similar numbers at KDEN yesterday 11/1900z, METAR 30.10 but in sim baro 29.83. The elevation on the ramp was correct for the in sim baro setting. This until I completed a preflight at the gate when all of a sudden the altimeter jumped to an incorrect elevation until the in sim baro was set again this time to 30.10. It’s as if some event unknown to me corrected the baro setting.

[TechyCentipede6]

Do you have the same issue if you follow the OP’s steps to reproduce it?

• YES, whenever I spawned on any airport with high elevation, e.g. KDEN, KTUS, KSLC. Press , (comma) key on keyboard to set altimeter from the sim. The value is different from the baro ref on the real METAR

Provide extra information to complete the original description of the issue:
• The value is different from the baro ref on the real METAR, always less than the real one

If relevant, provide additional screenshots/video:
• none

[Fornax4188]

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ISSUE DESCRIPTION

Description of the issue:
Totally wrong QNH/Altimeter at KDEN, live time, live WX- time 0020Z 3july.
Altimeter irl is 30.03, while in-sim it is 29.76.
At KSLC, not too far away, altimeter is correct (29.93).
Might be related to historical WX mixup, but with this discrepancy that seems too wrong.

WX/pressure in Europe was correct at EGCC an hour earlier.

Build 1.5.13.0

[CharlieFox00]

Something you can check - on the ground, using the in-sim (wrong) setting, what does it show for field elevation (and note where you are when you check that)?

And SLC is pretty far away (340nm) - the two cities can be and usually are affected by completely different weather patterns at any given time, especially with the Rockies between. I’d cross-check altimeters much closer - KAPA, KBJC, KFMM, KFNL, KGXY, KBKF, KEIK, or KCFO.

[DementedCorn327]

Seems something is going wrong for me too:

Live Weather
Spawning at KDEN RWY 08, C172 G1000, pressure is 29.76.
Field elevation is correct at RWY 08 threshold: 5364 ft.

Metar says 30.02:

Weather debug says 29.76:

If I click on B to get MSL pressure, Baro is set to STD (29.92):

If 29.76 gives the correct field elevation, could 30.03 that comes in the Metar be wrong ?
Clicking B should not set the pressure to STD.

[Fornax4188]

Yeah, I checked field elevation, and the irl live 30.03 was totally wrong.
29.76 gave me correct field elevation.

Checked DEN irl-Metar from different sources, all said 30.03.

Btw, I have bound ‘B’ to set local QNH(don’t remember set name you can bind it to), not 29.92/1013,2/STD, and it also set 29.76.

[CharlieFox00]

Weird. I wonder if one of the airports around there is giving 29.76 and is overriding KDEN. Or something else wrong in the ingest. Do any of the in-game ATIS or AWOS broadcasts around there say 29.76?

[DementedCorn327]

ATIS provides the same info than the pressure injected into the sim 29.80:

METAR reports 30.05

Windy.com reports 30.05:

FS2020 is injecting the correct pressure 30.04, so it seems something is wrong in FS2024.

[DementedCorn327]

After further tests, I would tend to say there an issue with airport in altitude, so not specific to KDEN neither SU3.

Live Weather. Pressure & temperature displayed on the G1000 are incorrect, they are not the ones from the METAR. Maybe some incorrect formulas are applied.
Nevertheless, terrain altitude displayed on the G1000 is the correct one.

KDEN (5,434 ft)

MMMX (7,320 ft)

SLLP (13,325 ft)

[CharlieFox00]

Oh weird! Yeah, that’s a problem. Wonder if there’s an algorithm that’s factoring in. Obviously altimeter settings are corrected to sea-level pressure, and both the ambient pressure and the sea-level pressure (QNE) are being calculated, per the debug tool.

Nice troubleshooting!

[TechyCentipede6]

Do you have the same issue if you follow the OP’s steps to reproduce it?

• YES, whenever I spawned on any airport with high elevation, e.g. KDEN, KTUS, KSLC. Press , (comma) key on keyboard to set altimeter from the sim. The value is different from the baro ref on the real METAR

Provide extra information to complete the original description of the issue:
• The value is different from the baro ref on the real METAR, always less than the real one

If relevant, provide additional screenshots/video:
• none

Is this server side issue or SU3 issue?

[HCDW135689]

Especially when i am flying over 10000ft,the QNH simulation is completely unacceptable!!!

Now i open the DEVELOPER MODE,open the Debug Weather Sim panel.

For example,now i am flying over the airport straightly with AGL 5672ft , AMSL17362ft,the ambient air pressure is 528.5hpa.After calculations,QNH is 1030.89hpa.However,i move to the ground(at same position),AGL 0ft , AMSL11722ft ,the ambient air pressure is 655.3hpa.After calculations,QNH should be 1019.18hpa.

As we all know,at same time,at same horizontal position,QNH should be same.But in MSFS live weather engine,there is over 10hpa difference!!!It is fatal when I am using RNP-AR approach!!!please fix it ASAP!thank you very much!!!

Only encountered when using MSFS live weather at High Altitude Airport both MSFS2020 and MSFS2024.It is OK when I use weather preset,custom weather and Active sky!Besides,it is ok when i using MSFS live weather at a low altitude airport!

REPRODUCTION STEPS

Please list clear steps you took in order to help our test team reproduce the same issue:

1. launch msfs2024 or msfs2020.

2. choose an high alt airport over 10000ft with msfs live weather on(for example ZULS)

3. press B button to set current QNH in sim

4. open DEV MODE,you can see the difference between AMSL AND INDICATED ALT!(It should be same when I set a correct QNH)

FREQUENCY OF ISSUE

Always when flying a high alt airport with msfs live weather on

[Pieter2427]

Another example:

Still present in SU5 Beta