I play NYGM and find that the weather has a big influence on how easy (or less hard...
) you can escape after they found you. If you manage to go deep in bad weather they will have trouble pinpointing you if you run slow and silent. Nice weather just cost me the end of a long career. One destroyer was sitting still finding me on the Asdic although I was 140m deep and the other one was making the attack runs. I escaped them for more than 1 1/2 hour real time until they got lucky and a depth charge damaged the bow. I had no time to order coming back to 90m safe depth, the light started blinking in the command post, water started leaking in and game over.
Which by the way means that it is interesting to go deep to try and evade detection, but is at the same time dangerous if the hull takes any damage.