I think you actually follow my point. You certainly in general follow the average but you adjust by the real time data. I don't know of another more practical apporach. You use average data for what it is to shape the general route
. But you also know that nothing is average so you adjust. Just because the average is at say a given lat you don't hold to the average course facing a non average moving storm.
The important part is you use averages before you leave so you can plan but you react to real information on the water