I always hope for very rough seas and stormy weather when finding a convoy. not sure if this would be the case in later years in the war with better escorts radar and HFDF, I am currently in July 1941 in a VIIC. A surface attack in those conditions I found will allow me to get, with care, through the escort screen and very close to the merchants without being detected. The stormy sea as well as limting visibility and risk of detection, I also found impedes the speeds of the escorts giving you a much more relaxed time frame to select your targets. In the ideal aproach with the compliment of three or four visible escorts, one in front of the convoy, one left and right etc, I have been able to sink two or three merchants ships before having to dive. Loosing escorts in that kind of sea state has been a cinch. Even running at full ahead, diving to 80 metres + and the escorts tracking and depth charging was way off. Rising to above 80 metres though I had to slow down, at those depths they could detect the boat. This of course enabled me to keep heading towards my next selected target at a speed which would either match it or close on it. Periscope attacks in rough seas are awkward at best, but if the escorts have really dropped the ball (you
) a rapid surface and UZO attack is possible. Tracking the targets with e-motors is hell on the battery life, but the increased ease of loosing escorts compensates for that. I found batterys of 25 % or just under was nothing to worry to much about. Between 2 and 8 minutes to loose escorts at slow speed in silent running mode has been the norm so far.