Night attack suggestions

[Tshark]

Hi Gang,

Looking for some suggestions here. I am in an early career mode and have found a convoy to attack. The problem I have is that during the day I have heavy fog that cuts down visual range too close to arm torpedoes. At night the fog lifts so that I can visually get an outline of the ships, but I do have heavy seas making a periscope attack almost impossible. I have tried a surface attack with TBT, but found that the TBT will not lock on a target (even though I can identify it well enough to match the identification manual). Hence, I can't get a range/speed and there are no range updates on the chart to do a three minute plot. By the time I get close enough for range/speed on target they are too close to attack. I figured I would try a sonar attack, but apparently my early year sub is only equipped with hydrophones. Every time I try to get a range I get the message "no target selected". Without a range I can't plot speed so an underwater sound attack appears out of the question.

Any suggestions on how to attack this convoy?