Final answer:
Polar air masses normally move in a westerly direction and tropical air masses in an easterly direction.
Step-by-step explanation:
In the Northern Hemisphere, polar air masses normally move in a westerly direction, while tropical air masses move in an easterly direction. This is due to the Coriolis force, which causes winds to be deflected to the right in the Northern Hemisphere. The counterclockwise rotation of cyclones, including hurricanes, in the Northern Hemisphere is a result of this deflection.