Understanding the Weather: Jan. 28,2008
Arctic air: A type of air mass whose characteristics are developed in the cold season over ice- and snow-covered areas of the far north. It has low temperatures, low moisture content, and is very stable. Air masses of arctic origin cover Chicago about six percent of the time.
Arctic outbreak: The rapid movement of a mass of air originating above the Arctic Circle southward to the Gulf of Mexico, or farther. Arctic outbreaks bring Chicago its lowest autumn and winter temperatures; also called "polar outbreak."
Cold wave: In popular usage, a period of very cold weather. Meteorologically, a rapid fall in temperature within 24 hours to temperatures requiring substantially increased protection to agriculture, industry, commerce and social activities.
Norther: In popular usage in the southern United States, especially Texas, a strong cold wind from the northwest, north or northeast. It is the cold outbreak associated with the southward movement of a frigid air mass.
Blue norther: In popular usage in the Southern Great Plains, a blast of bitterly cold arctic air that surges south across Texas during the winter, bringing strong north winds and a sudden, sharp temperature drop.