EYE ON THE SKY

Image Gallery Both ALTOCUMULUS (top) and ALTOSTRATUS (below left) clouds indicate precipitation in the next ten to 15 hours if wind is steady from between the northeast and the south.

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The secrets of weather forecasting
and preparedness.
By Matt Scanlon.

The sky was clouding over to the east and one after another the starts [the old man] knew were gone. It looked now as though he were moving into a great canyon of clouds and the wind had dropped. "There will be bad weather in three or four days," he said. "But not tonight and not tomorrow."

The Old Man and the Sea
Ernest Hemingway

In fact, nearly all but the largest TV stations simply grab the forecasts provided by the National Weather Service (NWS) and disguise them as their own. It would be foolish to completely discount their advice, but just as all our politics is inherently local, so is our weather. Individual communities have peculiar rainfall patterns, unique wind currents and other vagaries that defy a sweeping declaration of "scattered showers." The only way to guess with accuracy when it is going to rain or snow on your roof is to train your eye. With a crash course in cloud types, wind direction and speed, and what the frenzy of numbers in a forecast really means, you'll have a leg up on the national weather guessers... and a great excuse to stare endlessly at the sky without ever being accused of daydreaming.

The Anatomy of Clouds

Weather, for all its thousands of forms, storms and sunny days, is actually just nature's way of distributing heat. Every day, the sun heats the earth with energy equivalent to burning nearly one billion tons of coal. The earth's atmosphere, proportionally no thicker than the skin of an apple, takes the brunt of the radiation. If this incredible amount of energy were distributed evenly, pole to pole, we'd have an endless array of sunny days. Of course, we'd also have no rain, plants or life. Fortunately for us, temperature imbalances occur, not only because half the earth cools itself during the night, but because the poles reflect more heat energy than they absorb. Since the planet seeks balance, the excess heat in the tropics naturally distributes itself north and south from the equator. That distribution vehicle is wind, and in the face of constantly changing temperatures, water vapor blown into the atmosphere from oceans, lakes and rivers will often condense into clouds.

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