Yeah, the weather does seem a 'little' static most of the time. I consider myself lucky if I have any wind (or waves or rain) at all for the first 4-6 weeks of any patrol. Trouble is, I can't find any reference to which files are involved. I think there is a minor entry in the campaign/mission txt files but its far from being a control just something simple and seemingly insignificant. I thought maybe since the game was designed for the pacific environment that the weather was hard coded to be mostly sunny

also I think there may be some change depending on how far north or south you are. I play U-Boats in the atlantic and I think (I could be wrong, corrections welcome!) it is most unrealistic to have 4-6 weeks of flat calm in the deep atlantic anywhere north of Britain.
I does change occasionally though just it seems to kind of get stuck for a long time - sometimes the whole patrol... May be a bug, the previous games in the series had troublesome bugs with their weather systems. Anyway unless someone finds out why this happens or how to 'fix' it my watch crew will remain in their shades