Weather Forecasting
The U.S. Weather Bureau collects information from over 750 stations
4 times a day on wind speed and direction, types of clouds, temperature,
and barometric pressure. (We'll talk more about this later.)
If you watch the clouds, temperature, and wind direction where
you live, you can compare your cloud formations to the ones on your Cloud
Chart and begin to predict local weather conditions.
If you watch weather reports on TV you can fill in your National
Weather Map to see what kinds of weather ‘fronts’ are headed your way and
then you'll be able to predict what kinds of clouds are going to form!
Weather fronts are formed where two different kind of air masses meet.
(The slide in your weather kit is a picture of what happens when air masses
meet. It was taken from a weather satellite circling the earth.) If a cold
air mass ‘bumps’ into a warm air mass, you can be sure that bad weather
is going to occur. Using your Weather Symbol Chart, you can fill in details
of fronts on your map and, if you keep accurate records, you'll see patterns
develop which enable you to predict weather with a fair degree of accuracy.
Weather forecasting is mainly a job of careful observation and
accurate record keeping. With your Weather Kit, you can forecast whether
your family should plan outdoor trips or spend the weekend in a museum!
Building Your Own Barometer
Air pressure can be measured with an instrument called a barometer. If
the barometric pressure is rising, the weatherman will usually predict
fair weather and if its falling he'll probably predict bad weather. To
make your barometer, you'll need the balloon and rubber band that are in
the kit plus a straw from a broom, an empty tin can open at one end, a
piece of cardboard a little taller than the can, scissors, glue or tape,
and a pencil.
First, slit the balloon and stretch it tight and flat across
the open end of the can. Secure it tightly with the rubber band. Then,
glue or tape the broom straw across the top of the balloon with one end
at the center and the other end sticking out 2 inches beyond the edge of
the can. Fold cardboard in half. Cut it into an “L” shape as indicated
in diagram. Unfold base slightly and tape to can. Tape vertical edges of
cardboard together. Draw a line across the strip at the top of can.
Now put the can someplace where it will be undisturbed. It should
not be near a heat source, in a kitchen or bathroom or where sunlight can
hit it. Watch the straw for the next few days, If the air pressure increases,
it will push the balloon down, the straw will point up above the line end
and you're probably going to have nice weather. If the air pressure is
lessening, the air in the can will have more pressure than that outside
and the straw will point down below the line.