NavList:

I find myself fascinated by The World Sailing Ship Routes chart (Appendix A in both volumes of the new Bowditch).  The area I have reviewed most closely so far is the Hawaii to Vancouver route, which does indeed vary by season as the North Pacific High moves further north or south.  In looking to see who compiled this chart, I see that it was Sommerville (https://en.wikipedia.org/wiki/Henry_Boyle_Townshend_Somerville), who died in 1936.  

This put me in mind of how often the best expertise around winds and currents is a hundred or more years old.  Some of this knowlege is simply hard to acquire in this era of diesel engines.  Rather than spend weeks becalmed in an area - which provides ample opportunity to ponder seasonal variations in wind patterns - we fire up the "iron jib."  So some of the knowedge we want to acquire (diesel engines or no) is to be found in publications like this one, which is likely to be almost a century old. (I assume this chart was extracted from Ocean Passages for the World. Published for Hydrographic Dept., Admiralty, by HMSO [1923].)

James Smith was particularly interested in the winds and currents of the Mediterranean.  In the first half of the 19th century, he reviewed records of the British Admiralty in London, then moved to Malta from which he could interview a number of officers from the Royal Navy with extensive experience in "the Levant". 

His book, first published in 1851, The Voyage and Shipwreck of St. Paul, has been referred to by FF Bruce in his commentary on the book of Acts as one which - largely because of this specialized oceanographic knowledge - may be quoted but never superceded.  It has been made available as a reprint from http://wipfandstock.com/the-voyage-and-shipwreck-of-st-paul.html .

Smith was a member of the Royal Society and one of the first members of the Royal Yacht Club.  He had an exceptionally strong educational background.  He assumes that his readers are similarly educated, and thus fluent in Greek, Latin, French, Italian, and German.  So he is fascinating reading, if occasionally challenging to a monolingual reader like me.

Jimmy Cornell has attempted to update Somerville's work, and to take into account how climate change may be changing this earlier consensus around sailing routes.  https://cornellsailing.com/publications/world-cruising-routes/

Bob