Rain storm issue

[I'm goin' down]

It was raining. Extremely low visibility. My sonar man picked up a convoy. Due to the number of sonar contacts, it was a mid-size or large convoy. However, silouettes of the ships did not appear until they were within 1,000 yards, just about the time I could see them. I did see some lights in the mist when they were slightly further away. I could not use sonar only to attack because I could not get a fix on a single contact. I could not use the Dick O'Kane technique because I could not spot the ships far enough in advance to set up for a broadside shot. I tried to quickly set up for manual targeting by identifying the targets when they appeared out of the mist - setting the AOB, guessing at the target's speed, and using the SCAF mod to get the target's aspect ratio and range, but these efforts proved inacurrate because I did not have sufficient time to prepare. Thus, I missed two shots at a freighter from my aft torpedoes, and held fire on a second ship because it passed me at 90 degrees port and was out of gyro angle range of the forward torpedoes, and my aft torpedoes were in the process of reloading. Is there any technique that you can apply when visibiltiy is poor, the Navigation and Attack Maps do not pick up the target's silouette because of weather conditions until the target is almost on top of you, and setting up for a classic broadside is not possible? If it had been a solo freighter, the sonar attack would have been possible, but this was a convoy of ships, where getting a fix on a single ship (other than perhaps the lead destroyer) is next to impossible.