Persistent wind shifts are the ones that keep going one way and don't come back toward the original as in "oscillating shift". ..
These usually come from the moving weather system or a sea breeze. The weather system requires a good guess about when it will come in and will be more important in a longer race.
If you feel that a persistent shift has started, then sail the header to or near the lay line. If you are sailing the lift of a persistent shift, you will find that you keep being lifted and are a long time reaching a lay line. Some people call that the great circle route because the course keeps curving and is the long way to go.. (Note the other "great circle route" in global navigation is the shortest route.)
ANOTHER NOTE is that in the northern hemisphere the gradient wind is more from the right (as it rubs on the moving earth surface is turns left to form surface wind) so when gusts of gradient wind come down from aloft they are strongest from the right. If you don't know another good reason to go some place on the beat, go right in the northern hemisphere and left in the southern.
Some recent posts on my new blog
2 months ago