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Tuesday, April 8, 2014

A collision that won't raise your insurance rates

Googie precedes Google by 50 years, but you can combine the two and use Google to search for Googie. That's a neat trick, but what does that have to do with aviation?

Three things: the movement itself was inspired by the new Jet Age, the Theme Building (or "flying saucer") at LAX and the TWA Flight Center at JFK are oft-cited examples of Googie architecture, and the FAA's AC 00-6A, Aviation Weather, which you will need to become friends with as part of your ground study, is marinaded in hand-drawn examples of Mid-Century Modern art, right down to the cover:

State of the 1975 art. And that's the newest edition.
In case the title didn't give it away, Aviation Weather tells you what it's about right from the beginning:

Let's jump almost 40 years from 1975 to March 11, 2014, which is when I took this picture from the ramp at Lorain County Regional Airport:

As usual, you can click to embiggen.
There are two rows of undulating clouds at almost a right angle. The darker ones on the left go from the upper left and head toward the lower right, and the ones on the right go from the lower left and head toward the upper right. The left side is the lower layer of clouds and the ones on the right are higher (because they're being lifted by that lower layer, but we'll get more into that in a little bit).

Those two rows are a bit hard to see, so here are some psychedelically-enhanced versions (actually, just a moderately-solarizing filter in showFoto) that might help you see them a little better:

What would cause such an odd-looking sky? If you said, "Hey, I bet Aviation Weather would have the answer!" you'd be right. In fact, it has a whole chapter of answers:

Any time an Eskimo collides with a hula girl playing a ukulele, you know it's about to get real.

On this particular day, we had a stationary front hanging around over top of us, which was making for some (finally) warmish weather. Unfortunately, there was a cold front over Lake Superior heading our way to put out that fire, as this 7:00 a.m. chart shows:

That chart was from 7:00 a.m., and I took my picture at after 5:00 p.m., so that cold front had plenty of time to keep chugging toward Lake Erie. It arrived at around 4:00 p.m., as this data from Weather Underground for that day shows:

I drew a blue line across them at the time that picture was taken. From the top chart, you can see that the temperature was falling quickly, and from the bottom one you can see that the wind had shifted direction quite dramatically. That is the result of the cold front having arrived. As Aviation Weather puts it:

Temperature is one of the most easily recognized discontinuities across a front. At the surface, the passage of a front usually causes noticeable temperature change...

Wind always changes across a front. Wind discontinuity may be in direction, in speed, or in both. Be alert for a wind shift when flying in the vicinity of a frontal surface; if the wind shift catches you unaware it can get you off course or even lost in a short time.

We certainly got a "noticeable temperature change" and a change in wind direction, didn't we? That means we can be sure a cold front has passed. But what does that have to do with a picture of two cloud layers going two different directions?

If you said, "Hey, I bet he's going to put in another diagram from Aviation Weather!" you'd be right:

Figure 59 from the FAA's gloriously public-domain weather/art treatise.
The top half shows that while that cold front was passing through, it lifted the layer of warmer air that had been at the surface (attempting nobly yet vainly to thaw the cheeks of Clevelanders). That explains why there are two distinct cloud layers. The bottom half shows that the winds in the cold front are distinctly different from those in the warm front, so when it came through, the rows in the cloud layers shifted as well.

And that is how the pretty pictures from Aviation Weather combine to explain a pretty picture taken on a cell phone 40 years later. Do you have any weather pictures you'd like to share?

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