Thermal slanting and cloud alignment not improved after SU12

Bug Reporting Hub Weather & Live Weather
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1

Is it fixed as stated?
Yes
No
[X ] Partial

If no or partial, please give details below on your findings:

This is a tricky item to test but we’ve had three sim glider pilots testing it (or which 2 are RL glider pilots).

The thermal does seem to be biased to the upwind side of the cloud which is a great detail.

The thermal appears moving with the wind as is the cloud (i.e. we can climb in it mostly by simple circling) which is pretty realistic.

ISSUE: the upwind bias seems significantly more than it needs to be, i.e. we can circle upwind of the cloud and climb in that area continuing well above cloudbase without entering the cloud at all. Our testing suggests a couple of possibilities:

(a) there is a slope on the thermal in the direction of the cloud center (the lift visualisation tool definitely suggests this) but that somehow is affecting the visualisation much more that the actual aircraft, or

(b) we’ve stumbled upon an actual bug and the thermal upwind of the cloud is actually climbing vertically (in the airmass/cloud moving with the wind) without entering the cloud at all.

Regarding (b) we certainly seem able to climb vertically upwind of the cloud to the current max thermal height so there seems quite a possibility we’ve discovered a real issue rather than a needed tweak to the windward offset, but hopefully Asobo can make this assessment knowing their code.

For either (a) or (b) above, it seems likely any adjustment of the thermal less upwind of the cloud would improve the alignment.

many thanks.

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If no or partial, please give details below on your findings:

2

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Thank you for your work on improving thermal weather experience. Realistic thermal-cloud alignment is very important for gliding realism.
In support of the above bug report I’d like to present some of my observations.
Tests I performed were in Central Europe, low urban, flatlands area EPPR, EPKO, EPGI (where I fly in RL) date 15 July 2022 13:00 local time. All settings/assistance options set to realistic (including new turbulence assistance option).
Used presets tried to replicate typical european flatlands Cu Humilis weather - single cloud layer enabled with various not too strong wind settings: single 4m/s at ground (which MSFS significantly automatically increases with height), 4m/s at ground + 8m/s around cloud layer, in third scenario 4m/s at ground, cloud bottom and top. Example (reformatted horizontally for brevity):

obraz
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If no or partial, please give details below on your findings:

  1. CLOUD ALIGNMENT:
    WRONG situation: Thermals almost always tend to arrive at cloud base height several hundered meters too early in the upwind direction - outside cloud border. Often resulting in situation where thermal hits the side or even top of the cloud not its bottom.
    This is the same incorrectnes as case #7 on the picture Incorrect spatial relations between thermals and Cu clouds makes realistic glider flights impossible
    This incorrectness makes both searching for thermals unrealistic (they are way off from expected by RL glider pilot position in relation to cloud) and also allows (verified in test flights) to raise using thermal circling above cloud base (and even cloud top) without entering any cloud, which in typical conditions as set in weather settings (single active Cu cloud layer) should not be possible.
    Thermals too far in upwind direction from clouds also often means flying through clouds results in lack of expected lift/turbulence which was also reported in other threads from powered plane pilots.

EXPECTED situation: In described conditions (flatlands, single Cu layer) thermals should always enter given Cu cloud from its bottom, never hit Cu cloud from the side (as humid thermal arriving condensation height would condensate and create cloud there) and continue to raise exactly inside the cloud - in exact accordance to the cloud shape - towering Cu parts should have the greatest lift under and inside cloud.
RL Glider pilots use cloud shape - towering parts with dark flat cloud base to aim for the strongest lift - thermal core (it is ok to have several thermal cores under larger clouds).

  1. THERMAL SLANTING:
    WRONG situation: MSFS Thermals seem to slant/bend (even in 3layered constant wind scenario) at higher alt even more horizontally (flatten) towards cloud.

EXPECTED situation: Due to releasing latent heat Cu clouds generate additional lift and suck additional air directly from below cloud - please read: Cloud suck - Wikipedia
This additional sucking power should make lift vector even more vertical near cloud base.
Please see illustration quoted from Catching the Drift: Thermals and Wind - Flybubble :

obraz
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Please observe shape and the significant steepening (more vertical) bending of thermal when nearing to the cloud base height.

While it is ok to flatten a bit in medium height range - as wind speed tend to increases with height, the power of “cloud sucking” should overcome this tendency near the cloud bottom.
Glider pilot near the cloud base (say from 300m to cloud base) won’t search for lift outside being directly below the cloud, while in MSFS due to bending in the opposite direction glider pilot would have to search for it hundered meters upwind, outside from the cloud border.
I’d say provided picture is even a little bit exaggerated as the strongest lift 3m/s red dotted line should be more inside thermal and not directly on the leading upwind edge of thermal.
It is ok and even expected (as often the best exit from thermal is in the upwind directon) to find some lift and thermal bubbles in the upwind direction, but those air bubbles won’t be large enough to provide on average stronger lift than the stable core underneath the cloud - they may also condense in tinier transparent cloud pieces.

This issue may probably somewhat be remedied increasing strength of MSFS “cloud thermals” (that MSFS probably use to generate lift under stormy clouds), but please do not make it uniform - lift under thickest parts of cloud should have strongest factor. Large horizontal size of cloud doesn’t mean everywhere below cloud the lift is strong enough to lift the glider - there should be significant, stable thermal core(s) under cloud with diameter 250-500m with gradual lowering of lift strength outwards core.

This additional slanting may worsen above cloud alignment issue, and making it more steeper near cloud bottom may help repair it, but fixing thermal - cloud alignment is the main issue and it is better to postpone any quick changes to bending if this could worsen thermal-cloud alignment.

Please also note that issue https://forums.flightsimulator.com/t/the-height-of-the-clouds-does-not-correspond-to-the-settings-in-the-weather-presets/578413 (probably existing pre-SU11) where cloud layer visualization height does not correspond to height set in weather settings may also affect correctnes of thermal trajectory simulation (particles may travel according to settings, but cloud may be visualized at incorrect height).

Thank you for working on improving thermals/turbulence it is very important not only to glider pilots, but also for other pilots expecting clouds to give them updrafts/turbulence.

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Do you believe this issue is fixed?

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These errors are not fixed.
In the picture I demonstrate what we have in SU12-beta:

The blue line is the spiral trajectory of the glider in the centered cylinder of the thermal.
The red line is the trajectory of the rise of the center of the thermal cylinder (the maximum value of simvar “AMBIENT WIND Y”).
Green lines are 3D-termal visualization lines.
The cloud, the thermal axis and the 3D visualization lines-termal - move evenly in the wind.
The thermal axis and the 3D-termal visualization lines are quite rigidly “tied” to the cloud and are always located on the windward side of the cloud.
The glider, rising vertically along the axis of the thermal cylinder of the thermal, turns out to be outside the cloud, which does not correspond to real life at all.
In SU12-bet, the axis of the thermal cylinder of the thermal has no inclination and is not directed under the cloud! This is a mistake that does not correspond to real life.

I also suggest to see how this happens in MSFS:

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5

Do you believe this issue is fixed?

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[X ] No
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The thermals do not really connect with the clouds. They seem to be offset by a fair amount. See Video

Tested in Namibia, FYHO
Date: December
Time: Noon
Wind: 15 kts
Weather preset attached
Su12Beta_Separate_Thermals_Med_Wind_No_Gusts_v1.WPR (3.3 KB)

https://streamable.com/7bhefj

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6

Do you believe this issue is fixed?

[ ] Yes
[X ] No
[ ] Partial

If no or partial, please give details below on your findings:

Cloud thermals are clearly tied to the clouds, located on the windward side, but significantly shifted from the cloud!

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7

Voted!
I thought that we will be happy with thermals, turbulence in clouds etc with SU12…
But…
:pray:

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8

During the last Q&A Seb said that while the visualization of thermals is slightly off under clouds, they are in actuallity where they are supposed to be.
So turning the visualization is not helpful in this case.

9

It is NOT just a visualization issue.
This is actually where you’ll find lift in a glider.

This has been confirmed by many active members who fly hour-long cross-country tasks in our Sim Soaring Club community, both in live and preset weather.

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10

I would further add that there are no “blue thermals”. It looks like thermals are only present when there are clouds?

11

There is plenty of rising air in the absence of clouds, as long as you fly in Summer / Noon / Hot temperatures / Over cities / fields.

But it is very patchy and does not really form well defined bubbles of rising air, unless you find a big patch of one of the above mentioned landclasses (mostly cities).

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