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Which way is the air blowing? We explain the Washington Monument's bewildering wind currents.
Capital Weather Gang • Analysis
Which way is the air blowing? We explain the Washington Monument’s bewildering wind currents.
Flags illustrate a wacky pattern at the Washington Monument during a recent windy January day. (Matthew Cappucci)
By Matthew Cappucci
January 30 at 3:15 PM
Something did not seem quite right on a recent January afternoon.
The wind — from the northwest — appeared to be blowing in opposite directions on either side of the Washington Monument.
A closer look at the flags in the lee of the Washington Monument during a recent windy day in Washington. (Matthew Cappucci)
Five minutes, 10 minutes, 15 minutes ticked by. The wind did not change. And neither did the flags. Almost all of them fluttered in the “correct” direction of the wind, except for several, which were stubbornly defiant.
Naturally, I had to investigate — and so, like a transfixed tourist, I orbited the monument step by step several times to mentally map the wind field. (I would have climbed each flagpole with my pocket anemometer, but that might have raised some questions with authorities.)
It turns out there was not any magic trick going on at the Washington Monument that day. Instead, it was probably a classic example of “Von Karman vortex shedding.” Allow me to explain.
{snip}
Von Karman vortices appear downwind of the Canary Islands in this 2010 satellite image. (NASA)
{snip}
Hat tip to my friend Camilo Castellano-Sanchez, who first noticed the erratic behavior of the flags, motivating me to investigate further.
Matthew Cappucci
Matthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy. Follow https://twitter.com/MatthewCappucci
Which way is the air blowing? We explain the Washington Monument’s bewildering wind currents.
Flags illustrate a wacky pattern at the Washington Monument during a recent windy January day. (Matthew Cappucci)
By Matthew Cappucci
January 30 at 3:15 PM
Something did not seem quite right on a recent January afternoon.
The wind — from the northwest — appeared to be blowing in opposite directions on either side of the Washington Monument.
A closer look at the flags in the lee of the Washington Monument during a recent windy day in Washington. (Matthew Cappucci)
Five minutes, 10 minutes, 15 minutes ticked by. The wind did not change. And neither did the flags. Almost all of them fluttered in the “correct” direction of the wind, except for several, which were stubbornly defiant.
Naturally, I had to investigate — and so, like a transfixed tourist, I orbited the monument step by step several times to mentally map the wind field. (I would have climbed each flagpole with my pocket anemometer, but that might have raised some questions with authorities.)
It turns out there was not any magic trick going on at the Washington Monument that day. Instead, it was probably a classic example of “Von Karman vortex shedding.” Allow me to explain.
{snip}
Von Karman vortices appear downwind of the Canary Islands in this 2010 satellite image. (NASA)
{snip}
Hat tip to my friend Camilo Castellano-Sanchez, who first noticed the erratic behavior of the flags, motivating me to investigate further.
Matthew Cappucci
Matthew Cappucci is a meteorologist for Capital Weather Gang. He earned a B.A. in atmospheric sciences from Harvard University in 2019, and has contributed to The Washington Post since he was 18. He is an avid storm chaser and adventurer, and covers all types of weather, climate science, and astronomy. Follow https://twitter.com/MatthewCappucci
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