Very very good question. The answer, if there is one, is loaded with a lot of history. My summary that follows is based on my engagement in the forums over the past year and a half, so if I’m missing key parts of what has transpired, please feel free to correct me.
Shortly after the sim was released, people started noticing that live weather was very inaccurate. It wasn’t happening to everyone, but a good portion of users were definitely having issues. Now, I’m not talking about live weather being completely down (that’s a separate issue). What I’m referring to is users loading into a flight and seeing wildly different weather than what was forecasted and observed for that area.
Asobo had decided to completely close off the weather system to any third parties and had provided very few details on how the weather system actually works. Yes we had the feature discovery videos and Q&As so we knew some things, but without granular details, many of us were left guessing as to how the system gathers and interpolates the weather data, how it’s delivered to us, and most importantly…when it’s delivered to us.
Due to that lack of knowledge and not knowing what to expect as output from live weather, the forums became rampant with discussions of using METAR instead of Meteoblue’s weather model. Many users began comparing METARs to what was depicted in the sim at any given time.
After some time though, a bunch of forum users started really observing and began to identify trends. Eventually, it was discovered that for about half the day, every day, the live weather system was incorrectly rendering the wrong forecast hour, pushing it ahead by almost 12 hours. This was the actual cause of a lot of users seeing incorrect weather. Not a problem necessarily with the weather modeling itself or lack of METAR data, but a problem with delivery.
During that time however, Asobo began to inject temp, pressure, and winds from METAR into the simulation as a supplement to Meteoblue’s weather model, and that’s the way it had been up until the recent changes introduced with SU7. I found that this worked pretty well as it allowed for the correct assignment of runways for ATC users and provided an accurate baseline to determine aircraft performance on landing and takeoff. The visual weather wasn’t always a 1:1 match with METAR, but it was reliable enough to determine whether you prepare for VFR or possible IFR conditions.
After the forecast hour issue was fixed, the forum discussion of live weather inaccuracies dropped dramatically. Yes there were still minor issues like missing visibility, temperature spikes, overdone lightning, etc., but for the most part things settled down and weather was mostly accurate for a lot of people. However, by that time Asobo already began developing plans to overhaul live weather.
My point with all this is that it feels that SU7 is the result of Asobo attempting to fix live weather inaccuracies based on assumptions everyone was making earlier this year even though many of those problems were rectified by an entirely different solution. It also seems to be to cater to those simmers who for some reason expect to see a 1:1 representation of what METAR is reporting. Those legacy simmers for decades became used to METAR based weather systems in flight sim, especially those who fly in online networks like VATSIM.
Personally, all I think they really needed to do was find a way to add in visibility, improve the transitions of METAR (temp, pressure, and winds) and improve the accuracy of preciptation. I think they’d be better off sourcing visual weather data (clouds, vis, precip) from non-METAR sources. METAR has inherent limitations to the data it reports (ie. 10SM visibility limit, cloud layers only up to a certain height, etc).
But unfortunately, we are where we are now. I assume that the data sets provided by Meteoblue have changed with SU7, and the idea of making METAR optional may not be possible without Meteoblue providing two different data sets, one for SU7 weather and one for pre-SU7 weather, if indeed that is how it’s working.