Guten Tag,
The GWX supermod includes a weather fix, which should reduce stormy weather to days instead of weeks. My sense is that it's more effective if one stays in the game rather than saving, exiting, and reloading.
Re what to do when there's a ship or convoy and the weather's absolutely rotten, as in RL sometimes all you can do is report the contact (using h.sie's hardcode mod, this can have consequences):
http://www.subsim.com/radioroom/showthread.php?t=174225
I recall at least once shadowing the contact until the weather improved. But one has to be careful with TC; if visibility improves a lot, the enemy could spot you, too. A surface attack during a storm is sometimes feasible -- the danger there is that the ship might only become targetable when it's practically running over you. IRL kaluens tended to refrain from attacking in fog, and if they sank even a few ships on a patrol, they counted themselves lucky.
Gute Jagd!