Thursday, August 30, 2012

Weather Aware
By Michael

The Chaotic Pendulum in motion.
I remember days in my Washington, DC life when I’d leave my climate controlled office wearing a light jacket, surprised that cold, gusting winds were blowing snow flakes around my head.
“Christ!” I’d say to a bundled-up coworker, “I didn’t know it was going to snow today; it was pleasant yesterday.”

“They announced it on the news last night.”
“Huh, I missed that.”

Those days are gone. I can’t think of a lifestyle that would keep me more in tune with the weather than the cruising lifestyle. Windy and I often know what the conditions are where we are and what they are at a weather buoy twenty miles offshore. We usually know the forecast for the next ten days and how that forecast has evolved over the past 48 hours. When we’re passage planning, we look at the forecast twice a day—covering a 500-mile stretch of coastline. Planning two trips across a shallow inlet in King Salmon recently, we could tell you on what hour the high and low tides fell those days. Will there be moonlight on the nights of that upcoming passage? We know.
Eleanor quenching her
thirst at a drinking
fountain in the museum.
And the nightly news is no help in our pursuit of weather info. For the past year we’ve used and the features of the Navimatics navigation app on our iPad. Using, we select an area that encompasses our route and then can watch an animated 7-day wind forecast for that area. It has proven to be extremely reliable and we depend on it. From the Navimatics app, we are able to query data from specific weather buoys (data from en route that provide real-time local wind data that reaffirms the PassageWeather info, as well as wave heights that let us know what kind of a ride we can anticipate. Too we use other sources and our VHF radio weather channel broadcasts that are available along the U.S. coast.

I’ve always heard how difficult it is to predict weather, how the ever-increasing speed and computing capacity of super computers is being brought to bear on the problem, but that there is still a long way to go. I accepted this, but I never understood the reasons for it until we took the girls to San Francisco’s Exploratorium. There, they had on display a Chaotic Pendulum that made it all clear. This thing has three interconnected pendulums that all swing about the same axis when a knob is turned.
Apparently (and intuitively), there is no reasonable way to predict the movement of the interconnected pendulums. While the movement of a single pendulum would be easy to predict with knowledge of mathematics and the input forces, it is exceedingly difficult with multiple, interconnected pendulums. Not impossible, but any very slight error in terms of the input forces or the friction on a single arm, anything…and the calculus of the motion quickly becomes flawed, at odds with reality.

And so it is with weather systems. When multiple areas of circulating high and low pressure systems collide in a three-dimensional space, it is just like the Chaotic Pendulum—nearly impossible to predict the outcome, except in the very near term, such as related on the nightly news, for those who pay attention.

An interesting aspect of marine weather/wind forecasts is the nature,
or pattern, of the air flow. Out at sea, air masses flow uninterrupted
by changing topography--an additional contributor to chaos.
This results in consistent flows over large geographic areas. In this screenshot, note the difference in
wind direction and strength over land and sea (this is the
entire coastline of the Baja California peninsula).

Eleanor standing before the Palace of Fine Arts, just outside
the Exploratorium and built in 1915.

Also at the Exploratorium when we visited was a full-scale
mock-up of the Curiosity rover that just landed on Mars.
Have you seen Seven Minutes of Terror? (You must.)


  1. We loved the Exploratorium when we were in San Fran earlier this year. Bet we would have liked it even more if we'd been with you guys. Miss you all!

  2. Weather may mean life or death for you now! Not much of an issue in DC when you can dash into Cosi, Starbucks, on the way to the Metro. Glad you are keeping safe!


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