Friday, December 23, 2011

The Untold Story of How Santa Claus Really Comes to Town

Contrary to popular belief, Santa Claus' main weather concern on Christmas Eve is not snow, sleet, and rain, but wind.

He used to have problems with snow, sleet, and rain, not to mention fog and other visibility obstructions, but these haven't been a concern since he added Rudolph to his team many decades ago.

Source: Rankin-Bass Productions, Inc.
Instead, Santa's primary concern is wind.  To deliver presents to roughly 800 million homes, Santa has to travel 160 million miles (see Fermi Lab analysis).  He has a whole night to do this, so if he can work his way around the globe delivering presents over a 24 h period, he needs to maintain an average speed of 6.7 million miles per hour (1850 miles per second).

Santa travels mighty fast, which is why you can't see him.
Santa has strong reindeer, but you don't want to further stress them by flying into a headwind.  Keep in mind that the sun moves from east to west, so Santa is working his way westward and, since much of the world's population lies in the mid latitudes, he is working against the mean westerly jet stream.  Further, the southern hemisphere mid-latitude jet stream ain't a heck of a lot weaker in summer (which is what they are presently experiencing) than winter, so this is a chore in both hemispheres.

But, Santa has an ace in the hole.  He has some elves who used to work at Google and are incredible programmers.  Using the global weather forecasts from the National Centers for Environmental Prediction and the European Center for Medium-range Weather Forecasting (ECMWF), combined with Santa's naughty and nice list, they have optimized Santa's route to minimize head winds and reduce wear and tear on Donner, Blitzen, Dancer, Vixen, Prancer, Dasher, Comet, Cupid, and Rudolph.

This is the real miracle of Christmas.  Santa has been able to leverage numerical weather prediction to continue to deliver gifts to an exploding global population.

Merry Christmas from the Wasatch Weather Weenies.

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