During the Spring, we start to see some awfully wild weather and it all has to do with the changing of air masses. You may have heard the term air mass before but what exactly is an air mass. An air mass is an extremely large body of air whose temperature and humidity are fairly similar over a large part of an area (think the cold air that comes from Canada behind any given cold front).

Regions where air masses originate are known as source regions. Air masses are usually classified according to their temperature and humidity. There are cold and warm air masses and humid and dry air masses. Air masses are grouped into four general categories according to their source region (region where they develop). Air masses that develop in the cold polar region are designated with the capital letter “P” for Polar. Those that develop in warm tropical regions are designated with the capital letter “T” for Tropical. If the air mass originates over water, it will be moist (humid) and the lower case letter “m” will precede the capital letter “P” or “T”. If the air mass originates over land, it will be dry and a lower case “c” (continental) will precede the “P” or “T”. In North America, there are four types of air masses.

Continental Polar (cP)/Continental Arctic (cA)

This air mass is associated with the bitter cold air that invades southern Canada and the United States in winter. This air mass originates over northern Canada and Alaska.Maritime Polar (mP)

This air mass is associated with the cool wet pattern in the Pacific Northwest United States (rainy & cool Seattle). During the winter, cold air originating over Asia and polar region move southward, across the Pacific. The ocean’s effect warms and moistens the air, this is why the Pacific Northwest stays wet and cool. In fact, many of our storm systems in the U.S. originate in this region before moving eastward.Maritime Tropical (mT)

The warm air of southern California, Gulf of Mexico, as well as the Caribbean is associated with a maritime tropical air mass. This air mass in the Pacific originates near the Hawaiian Islands. The southern U.S. stays warm because of the maritime tropical air masses that originate near the Gulf of Mexico and the Caribbean.Continental Tropical (cT)

During the summer, this air mass originates over northern Mexico. The hog, dry air that is present over the desert southwest of the U.S. is associated with this air mass.

In the Spring and Summer, it is important to study these air masses because it is the clashing of these air masses that cause such turbulent weather during this season. These air masses are separated by cold and warm fronts as well as the jet stream (fast moving column of air about 6 to 9 miles above our head) that steers storm systems. In fact, it is the Continental Polar/Arctic (cP/cA) from Canada and Maritime Tropical (mT) from the Gulf of Mexico air masses clashing that cause so much severe weather, including tornadoes, flooding and lightning, in the Great Plains states this time of year.

No matter what the weather, you can always count on your First Alert weather team to keep you ahead of any storm. You can always follow the forecast on our website or download our mobile app and the itunes and google play stores.