[Boasun]

Also a rapidly passing Low will cause the wind to either back or veer as it goes by. And the inversion could be adding to it also.

 

[Boasun]

In some areas where you will find wind eddies. Small ones could be caused by an anchored large ship. Bluffs can cause a change. Plus a fast moving Low or High can cause wind veers & backings. Then you may have a combination of any of the above. So watching the Cat's Paws on the water is a good tattle tell for one. Watching the sails of other boats around you and another way.
For an example: Saw a boat with a skinnaker set & flying...the next moment they had a spinnaker wrap around the fore stay. Which fore told a strong gust and change of direction coming our way. Yep we got knocked down. But then she righted herself. Lucky us.