An air mass is an extremely large body of air whose properties of temperature and moisture content (humidity), at any given altitude, are fairly similar. Air masses can cover hundreds of thousands of square miles.
Air mass source regions are geographic areas where an air mass originates. Source regions could be over land or water. The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below.
Continental -located over large land masses-dry Marine-located over the oceans-moist
Tropical latitudes are typically located within about 25 degrees of the equator. Polar latitudes are typically located near the poles of 60 degrees north and south or more.
Four combinations of air mass: cT – Continental Tropical – dry and warm mT-Maritime Tropical-moist and warm mP-Maritime Polar–moist and cold cP-Continental Polar–dry and cold
Air mass in the U.S. cP–Begins in Canada, just North of US border, and moves South towards The Great Plains. Bitterly cold and dry! mP–Begins in Pacific Ocean off the coast of Alaska and moves Southeast towards Washington & Oregon. Very cold but with lots of moisture. mT–Begins off the coast of either Florida or Baja California. The air masses move North toward towards either coast and inland passing over California and Florida as they move. Very warm with lots of moisture. cT-Begins over Mexico and moves North passing over Texas. The air is warm but very dry.
The Jet Stream Cold polar air flowing down from the north meets the warmer air mass over the United States causing the polar jet stream to form. The Jet Stream is a narrow belt of strong winds that blows near the top of the troposphere.
The Jet Stream The jet stream tends to influence weather by bringing cool, dry air southward, causing heavy thunderstorms and a drop in temperatures. At times, the polar jet stream may dip further south into the U.S., bringing cold weather with it. At other times it retreats into Canada, leaving milder weather in the U.S