Air flows are not flat like the MSL. They have
depth and breadth, and are affected by local geography. At the same time,
weather forecasts are based on average
wind speeds, unimpeded.
SF Bay, a wonderful place to sail, but just as the local hands are describing, there are places where the
wind seems to go away. It hasn't, it's just flowing around Angel Is, or romping down off the hills on the Marin side, 25 knotting down the city front, and calm for a lunch stop in the lee of the island.
Enjoy.
Ann