Several different types of air masses affect the continental United
States. The Gulf region is particularly influenced by the maritime Tropical
air mass in the summer when the jet stram has migrated north. It is influenced
by the position of the jet and the interplay of the continental Polar and
maritime Tropical air masses in the winter. The Arctic air mass occasionally
affects winter weather.
Arctic Air Masses develop around the Arctic, and are characterized by
being cold from surface to great heights. The boundary of this air mass
is often defined by the Arctic front, a semi-permanent, semi-continuous
feature. When this air mass moves from its source region, it may become
more shallow in height as it spreads southward. Continental Polar air masses
occur over high latitude regions. Continental polar air (cP) is formed
over cold surface regions and is typically very stable with low moisture.
Maritime Tropical air masses form in the tropics or subtropics over the
low latitudes. Maritime tropical air is produced over oceans and is warm