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Many signs of a weather change heading your way are given by animals(1). When a low-pressure system is bearing down on you, quail and other birds will dust themselves more frequently and vigorously. Frogs such as the spring peeper will sing more often and more intensely. Swarming insects that buzz busily when a storm is a few hours out will suddenly stop when a storm is right on top of you.
But that's not all. Spiders won't spin webs if a storm is about to hit, and gulls and other shorebirds will gather in inland parks and fields. Elk, bighorn sheep and other alpine animals will come down out of the high country when a storm approaches and head back up as it departs. Finally, listen. Sound carries better under a low-pressure system, making things you might not hear under high pressure quite audible.
Knowing your clouds will help you predict the weather.
Altostratus are grayish, sometimes with a tinge of blue. They can be thick and cover the entire sky. Storms are likely ahead.
Altocumulus are puffy and gray and if you see them on a humid morning, a thunderstorm could be imminent. They can appear as waves and may vary in shade.
Stratus cover the whole sky, and usually mean light rain or drizzle. They can be formed when a layer of air moving in below it forces it up. Did you know that fog is a stratus cloud on the ground?
Statocumulus hold little rain. They're low, gray, and lumpy and come in rows, masses or patches.
Nimbostratus are dark gray and produce continuous but not heavy rain. They blot out the entire sky.
Cumulus look like cotton balls with flat bases. They form when blobs or warm, moist air float upwards from the Earth's surface. They mean fair weather if they don't grow vertically very much.
Cumulonimbus is the Big Guy known to spew tornadoes, hail, lightning and heavy rain. It's anvil-shaped with a flat bottom and a towering center. The top of the anvil may be diffused by winds.
Cirrus clouds are bunches of ice crystals. They get their comma-like tails when some of the ice crystals in them start to fall. Airliners make cirrus clouds when the water vapor from their engines freeze into ice crystals. If the trail vanishes quickly, the weather will be good. If it lingers, you may be in for a storm.
TRY IT! Try making your own clouds(2). A great project for the kids! You'll need a match and a 2 quart glass jug with a narrow neck. Turn the jug upside down and hold a lit match inside the mouth of the jug for about 5 seconds. Wait until the glass cools then put your mouth over the mouth of the jug so that it's completely covered. Blow hard and try to force some air into the jug. Watch what happens inside the jug when you take your mouth away.
You supplied the first ingredient when you let the match burn into the bottle: soot. The soot particles are so small that you can't see them. But without particles of some kind, no cloud will form.
The second ingredient was warm, moist air from your breath. On a summer day there are about eight milk cartons full of water in a chunk of air that would fill a classroom. This water has been sucked out of lakes, rivers and oceans by evaporation.
The air in the jug cooled suddenly when you took your mouth away. The air in the sky cools as it rises. When air is cooled, some of the water vapor condenses. It turns back to a liquid on the tiny particles in the air. The result: tiny water droplets. A cloud is just a huge crowd of tiny water droplets.
So enjoy making clouds and see if you can predict the weather next time you're out!
1. Newman, B.,1997. Weather or not. Field and Stream. p 126.
2. Wyatt, V. 1990. Make a cloud in a bottle. Weatherwatch. Addison-Wesley Publishing Company, Reading, MA. p 22.
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