After reading the book Enigma, I believe that each boat reported back the weather of its current position to BDU quite often (I think Daily actually which was one of the first steps in deciphering the messages). I've also seen Captain's logs denoting the Sea state each day and the Barometric pressure. Obvious to any person with some weather knowledge....pressure falling would signify a Low pressure "system" (aka storm..bad weather and sea state)...pressure climbing would be the opposite
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I dont know if BDU would send out Isobars (lines of equal pressure) to the Uboats....that does not seem realistic in my mind. Nor did the obvious technology of advanced communication which didn't exist at the time ....fax...email...pretty pictures of weather.
What I do think is that the radio operator was capable of intercepting merchant radio chatter of bad weather...as this has always been common practice ..at least in peace time. I would think BDU would send "known" weather conditions to Uboats if it thought that it might effect operations or delay actions.....but I have not proof of that. I do know that BDU wanted strict radio contact with its Uboats early in the war (pre direction finding or suspected broken enigma code breaking)....and weather was passed all the time.
Unfortunately, until we have a "global" weather pattern in Simulators ...vice a change every couple of days...I dont think you going to get much out of weather maps. Personal opinion.