"What sort of things, sir?" asked Fred.
"Well, my boy," the Forecaster answered, "if there's an area of low pressure in Dakota, we know that it won't strike California; if there's one in New York, we know that Maryland is safe. A storm will never go down the Mississippi, nor up the St. Lawrence, but will always travel up the Mississippi and down the St. Lawrence."
"There does seem to be something regular about it," the farmer remarked, his interest growing, as the Forecaster took his pencil and sketched out, across the map of the United States, the five great storm tracks. "That's all right for storms, maybe. But how about a cold wave? Fred, here, said that a cold wave was coming. Can you figure that out in the same way?"
Measuring the Blizzard's Rage.
Shielded snow gauge in the Northwest to register the amount of snow-fall.
Courtesy of U. S. Weather Bureau.
"Certainly," the weather expert answered. "As a matter of fact, it is comparatively easy. A cold wave is simply a fall of temperature caused by the cold air from the upper atmosphere sweeping downwards after a cyclone of low pressure has passed."
"A cyclone?" ejaculated Ross, in surprise. "Is there always a cyclone before a cold wave?"