Depends on how warm it is Andy "Blaw Hames" tend to bring the right conditions for good returns especially over in the west/central part of the country. On the other hand the "east" tends to be blessed with better "high pressure" weather conditions, but your point that you can get good races with good returns with north west winds is true.
HOWEVER if you look at the records, "high pressure" and light south west winds are still the most benign and benifical to our birds.