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View yaw angles, crosswinds and effective air speed.
At 40km/h (25mph) on flat roads the drag from the air hitting a reasonably aerodynamic cyclist will account for 77% of the power the cyclist is producing. When you factor in a headwind of 5km/h to achieve the same speed of 40km/h the rider would need to produce 36% more power!
Knowing when and how the wind will effect your ride can help you to prepare and execute your race in the most efficient way. Consider the rider who is going into the 5km/h headwind. Knowing beforehand that this is the likely scenario perhaps they will maintain a cool head knowing at what point on the course ahead the wind direction will change.
Running the deepest front wheel possible will get you the best time, right. On a wind free day yes. Now consider a day in which the winds are high. You may be nervous to put that 80mm aero wheel in so you leave it at home. But hold on, what if the course never presents the wind at an angle that would cause you trouble? By viewing the wind for the course you may have the confidence to run the deep section wheel knowing that the crosswind will be manageable for the course.
What if the course is too dangerous for the 80mm wheel. Find out beforehand by checking where on the course the crosswind will be and just how high the crosswind speed is.
We can't control the conditions but we can control our expectations. If the wind is unfavourable for the course you may want to adjust your targets for that race. Knowing in advanced how the wind will likely effect your target time is a good way to keep morale up. Especially when staring at your average speed half way through the race.
After a race knowing the conditions you raced in you can view how well you did with statistics such as Effective Air Speed. This shows the overall average of the air speed for the course. The wind direction, course orientation, your average speed and wind speed all effect the air speed encountered during your race. Use this information to compare your performance with other races.

Wind Lines and the concept of colours for the depiction of wind direction on a route map is the Copyright of Ben Norbury.
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