PKPF68-77
You are a weather person and so should be able to go over all the available information from all sources with an experienced eye – and not get stuck on the conditions at Mac - It was only very near the Mull that conditions were bad coming from NI – the cloud base was well up and the isolated patches at low level were evidently not a problem during the sea crossing. As I have said before, they would only have had a problem if they had had to approach very closely for some reason.
If you want to consider their airmanship and their a/c's capabilities you could look at their path over the Antrim hills earlier in the flight. Boeing's analysis has it that they must have kept very much on track and maintained their high cruising speed all the way to the position of waypoint change to have gotten there by the time they did. So you can assume a track of 027 and plot this on very large maps. You would then perhaps see that they had negotiated about 10 miles of hills with very little headroom beneath the cloudbase, presumably exercising the controls vigorously and demonstrating that they were not at all lacking in ability that day.
Indeed, it is amazing that, after that leg, anyone could entertain the idea that such a crew could not have avoided what is essentially an isolated low hill. However, as I have been saying for a while, if they had a need to go to a point on the Mull, the conditions were bad for visual judgement of range as they approached.