Well, hopefully the seas are rough. That will help mask your getaway or approach. I would try to gain some perspective of their course and speed and then come up to PD and sink the closest target with the highest probability of success. The fact that they caught you off guard means you're going to have to make due with your current ambush position, leaving you some, but little other choice.
Be ready to stay submerged for a while, depending on your current location, since there are 3 separate TFs that will be approaching and then departing the area. If you have to, you can actually back away from a target using either "back slow" or "back standard". This maintains your boats blading relative to the TF and any approaching DDs. I've also found that it seems a little harder for the DDs to hear you when you back away, as opposed to turning around, which you can do later anyway when sufficient distance is gained.
Good luck sir.
