This is a great chart to get an overall picture of the wind conditions for your event. The rise and fall of the Air Penalty chart depicts the headwind and tailwind sections by accruing Air Distance vs Ground Distance.

What is Air Penalty?

Air Penalty is the difference between Air Speed and Ground Speed over time. Air Distance is the distance or length of air travelled. We are used to completing a 10 mile time trial but in fact it may be a 10.5 mile air distance time trial. Where Air resistance is the major resistor to ground speed, which is most of the time except steep hills, Air penalty provides a good clue as to the speed of a course.

Using the chart

Headwinds raise the blue line, the greater the differential between ground and air speed the steeper the rise. In tailwinds the blue line falls. The resulting difference is the Air Penalty.