How to Forecast Weather

Enlarge Image Image Gallery North American air masses. ILLUSTRATION: MOTHER EARTH NEWS STAFF

 Men judge by the complexion of the sky
The state and inclination of the day . . .  

RICHARD II, ACT 2  

O ye hypocrites, ye can discern the fact of
the sky; but can ye not discern the signs
of the times?  

MATTHEW, 16  

When you're into farming it seems like all you do is wait for it to rain or wait for it to stop . . . and even if you're city-bound, a lot of what you do depends on the weather. While some folks argue that we ought to take pleasure in whatever the climate brings, there are times when its nice to know in advance what ol' Mother Nature has in store for weather forecast conditions tomorrow or next Wednesday . . . and that can be arranged quite easily once you know the secrets of down-home weather forecasting.

To an extent, you know, we're all weather forecasters already. If the clouds are dark and heavy and the wind feels and smells a certain way, we assume its going to rain. And it usually does. Complete, accurate weather projections are just an extension of this. Homesteaders observe and we draw conclusions from our observations.

Here, then, are some bits and pieces of scientific information, weather lore and personal observation to help you to know what to look for and what conclusions to draw. With a little practice you'll find that you, too, can become just about as accurate as the official weather forecaster on whom you probably now rely. It'll be one more apron string that you can let go of . . . and one more step toward independence.

Where Weather Comes From 

The first thing you'll need to know is a little about how weather works and the bare essentials can be explained quite simply: everything is caused by air masses. Meteorologists would probably recoil in horror at that simplification, but there it is.

These air masses are great lumps of atmosphere with fairly uniform temperature and moisture characteristics. They form over certain areas of the earth's surface (known as source regions), acquiring the temperature and moisture characteristics of the parent region in the process. These huge chunks of air are classified by temperature and moisture and named for the source area over which they form (see Fig. 1 by clicking the Image Gallery link above).

There are four basic types of air masses: Warm and Dry (Tropical Continental, indicated by the symbol cT); Warm and Wet (Tropical Maritime, mT); Cold and Wet (Polar Maritime, mP); Cold and Dry (Polar Continental, cP). The maritime air masses (those originating over the ocean) are sometimes subdivided and given names such as Gulf Tropical, Atlantic Tropical, Atlantic Polar, Pacific Tropical and Pacific Polar . . . all with appropriate symbols. The names really aren't very important though, just the characteristics.