Besides the pilot charts
, you can get the monthly average of wind as actually measured from the QScat satellite
program (alas now deceased) at:
Climatology of Global Ocean Winds - COGOW
There is also a program called Virtual Passage
which allows one to plot a course based on the pilot chart wind rosettes and currents and produces a summery as to how many days will be sailed, at what expected point of sail, and how much motoring (if one is inclined to do that), and how many days the voyage may take...
Once upon a time you could actually download QScat data on SailDocs for wherever you were or were going, and it was absolutely great. Now the satellite
has irreparable problems (I think with the antenna) and does not send data. Alas, alak, alay! Write your Congress Person...