Weather Whys; Air Masses

This is weather wise. The weather we see is generally the result of a clash between air with different characteristics. Those different kinds of air are called air masses, and there are four basic kinds affecting the United States. They're divided by temperature and moisture content. For example, a continental polar air mass is continental, meaning it originates over land, and the term polar indicates it comes from polar regions. As you might expect, such a system is cold and dry, and often sweeps down into the Midwest behind a cold front. A maritime tropical air mass comes from the ocean, and originates in tropical regions, so the maritime tropical air mass is warm and moist. It comes from the equatorial oceans, and is a significant source of moisture for thunderstorms. The other two kinds of air masses are called maritime polar and continental tropical. And as you'd predict, maritime polar air is cool and moist, while continental tropical

air is warm and dry. It's continental tropical air that affects the desert southwest in the summertime, encouraging the hot, dry conditions there. And maritime polar air sweeps into the cool Pacific Northwest and down the New England coast all year round. And the combination of two very different air masses can produce a volatile situation. For instance, in the spring maritime tropical air meets continental polar air in the Midwest, and often leads to severe thunderstorms. Weather-wise is produced with the assistance of the National Weather Service Forecast Office and the National Severe Storms Laboratory, both in Norman, Oklahoma, and the Cooperative Institute for Meza Scale Meteorological Studies, the Oklahoma Climateological Survey, and the School of Meteorology, all of the University of Oklahoma. For Weather-wise, I'm Drew Barlow.