Thankfully we are seeing a break from the heat and humidity this week. The maritime tropical air mass that had us in its grip last week is being shoved back towards the south…for now. What is this air mass and why does it get so hot and humid when it is around? Read on for the explanation.

Characterizations of a Maritime Tropical Air Mass


The two words that best characterize this air mass are warm (80F-90F in the summer) (70F-80F in the winter) and moist (dew points greater than 50F year-round). As far as stability is concerned this air mass is very unstable and light. This leads to the development of unsettled weather.

Development and Source of Air Mass

The maritime tropical air mass develops in warm ocean waters located in the tropics and subtropics. These types of air masses thrive in the South Atlantic, South Pacific, and Indian Oceans. Most of our mT air masses originate in the waters of the Gulf of Mexico and the Gulf Stream. The warmer bodies of water warm the overlying atmosphere and constantly supply it with plenty of rich moisture.

Where Do Our Air Masses Originate?

All of the incoming solar radiation allows these waters to stay very warm throughout the year. During the winter months, the mT air mass is kept away from the continental United States. The reason is the almost constant onslaught of cold air that we see push down from Canada.

What Type of Weather Can You Expect?

Due to its very moist and unstable nature, this air mass is responsible for most of the country’s thunderstorm activity. Remember that a thunderstorm needs a warm and moist environment to form. The maritime tropical air mass provides both of those conditions. In fact, most of the United States’ rainfall comes from the presence of these air masses.

Even without the thunderstorms forming, this air mass is noticeable. You only need to step out the door to notice the very humid nature of the maritime tropical air mass. This is the air mass responsible for the triple h’s currently plaguing the region. The triple h’s are hazy, hot, and humid conditions.

View of the Grip of a Maritime Tropical Air Mass on the River Valley from our Mount Magazine Magtel Co. Cam.

Modification of the mT Air Mass

As the maritime tropical air mass moves inland it starts to change its characteristics. The biggest change is in the moisture content. The maritime air mass starts to become drier the farther and farther north it tracks. The atmosphere inland tends to be much drier due to several factors such as lower sun angle, less moisture available, and cooler land. Often the mT starts to take on more continental tropical (cT) air mass characteristics over time. We will explore the cT air mass in a separate Weather 101.

For other exciting and interesting digital weather content, check out other Weather 101 and Weather Blog pieces.