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25 terms

Chapter 8 - Air Masses, Fronts, and Middle-Latitude Cyclones

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air mass
a large body of air that has similar horizontal temperature and moisture characteristics
back door cold front
a cold front moving south or southerwest along the Atlantic seaboard of the United States
cold front
a transition zone where a cold air mass advances and replaces a warm air mass
continental arctic
an air mass characterized by extremely low temperatures and very dry air
continental polar
an air mass characterized by low temperatures and dry air
continental tropical
an air mass characterized by high temperatures and low humidity.
convergence
an atmospheric condition that exits when the winds cause a horizontal net inflow of air into a specified region.
cyclogenesis
the development or strengthening of middle-latitude cyclones
divergence
an atmospheric condition that exits when the winds cause a horizontal net outflow of air from a specific region.
front
the transition zone between two distinct air masses.
frontal wave
a wavelike deformation along a front in the lower levels of the atmosphere. Those that develop into storms are termed unstable waves, while those that do not are called stable waves.
jet streak
a region of high wind speed that moves through the axis of a jet stream. Also called jet maximum.
lake-effect snows
localized snowstorms that form on the downwind side of a lake. Such storms are common in late fall and early winter near the Great Lakes as cold, dry air picks up moisture and warmth from the unfrozen bodies of water.
lee-side low
storm systems that form on the downwind (lee) side of a mountain chain. In the US lee-sode lows frequently form on the eastern side of the Rockies and Sierra Nevadas.
maritime polar
an air mass characterized by low temperatures and high humidity.
maritime tropical
an air mass characterized by high temperatures and high humidity
northeaster
a name given to a strong, steady wind from the northeast that is accompanied by rain and inclement weather. It often develops when a storm system moves northeastward along the coast of North America.
occluded front
a complex frontal system that ideally forms when a cold front overtakes a warm front. When the air behind the front is colder than the air head of it, the front is called a cold occlusion. When the air behind the front is milder than the air ahead of it, it is called a warm occlusion.
open wave
the stage of development of a wave cyclone where a cold front and a warm front exist, but no occluded front. The center of lowest pressure in the wave is located at the junction of the two fronts.
overrunning
a condition that occurs when air moves up an dover another layer of air.
polar front theory
a theory developed by a group of Scandinavian meteorologists that explains the formation, development, and overall life history of cyclonic storms that form along the polar front.
source region
regions where air masses originate and acquire their properties of temperature and moisture.
stationary front
a front hat is nearly stationary with winds blowing almost parallel and from opposite directions on each side of the front
warm front
a front that moves in such a way that warm air replaces cold air.
wave cyclone
an extratropical cyclone that forms and moves along a front. The circulation of winds about the cyclone tends to produce a wavelike deformation on the front.