The Gorilla Sprints to Victory!

German André Greipel, nicknamed the Gorilla, won Stage 6 today with a thrilling sprint to the finish line.  The image below shows Greipel just edging out his closest competitors (click on the image for a larger view).

Below is Greipel's winning time and a comparison with our prediction.

• Stage 6:  4h 11' 39" (actual), 4h 29' 39" (prediction), 18' 00" slow (7.15% error).

Greipel's average speed is given below.

• Stage 6:  12.85 m/s (46.25 kph or 28.74 mph)

Why are we slow again?  We are slow for the same reason we were slow the past two stages:  tailwinds.  Cyclists traveled essentially southeast today.  Winds from the northwest to the southeast in the range 15 kph (9.3 mph) - 20 kph (12.4 mph) dominated the stage.  Check out the image below from early in the race (click on the image for a larger view).

Look at the flags!  The wind is blowing right in the direction of the stage's route.  I saw flags like those all through the stage while I watching the race online.  Below is another screen shot I took, this one near the end of the race (click on the image for a larger view).

The poor guy holding the French flag can barely hold it as the wind is blowing right in the direction the cyclists are moving.  Tailwinds have been a theme in the past three stages.  We aren't making excuses for bad predictions, but we are putting into context why we are slow.  We simply didn't have weather information before making predictions.  Had we averaged over all the winds, including the crosswinds near the end of the stage, and put in a 5 kph (3.1 mph) horizontal tailwind for the entire stage, we would have been just 22" fast.  In the future, we may have to guess weather conditions based on what we've learned about northern France.

Stage 7 is the second-longest stage in this year's Tour de France.  Cyclists will bike 234.5 km (145.7 mi) tomorrow.  Beginning in the commune of Épernay, riders will move mostly east for the first half of the stage, followed by an essentially southeast route toward the finish in the city of Nancy.  Sprinters need to get good times tomorrow before hills and mountains greet riders in the following three stages before the Tour de France has its first rest day on 15 July.  Below is our prediction for Stage 7.

• Stage 7:  5h 27' 13" (prediction)

If you are watching tomorrow's action and note tailwinds, our prediction will likely be too slow.  We are hoping to see a stage without significant contributions from the wind!