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dryline
A boundary that separates warm, dry air from warm, moist air. It usually represents a zone of instability along which thunderstorms form.
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 ahead 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.
overrunning
A condition that occurs when air moves up and over another layer of air.
stationary front
A front that 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.
air mass
A large body of air that has similar horizontal temperature and moisture characteristics.
"back door" cold front
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.
jet streak
A region of high wind speed that moves through the axis of a jet stream. Also called jet maximum.
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.
cold front
A transition zone where a cold air mass advances and replaces a warm air mass.
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.
The name given to the low pressure area that forms or re-develops on the eastern side of the Rockies, then rapidly skirts across the northern tier states of the U.S. is the:
Alberta Clipper
continental arctic (air mass)
An air mass characterized by extremely low temperatures and very dry air.
maritime tropical (air mass)
An air mass characterized by high temperatures and high humidity.
continental tropical
An air mass characterized by high temperatures and low humidity.
continental tropical (air mass)
An air mass characterized by high temperatures and low humidity.
continental polar (air mass)
An air mass characterized by low temperatures and dry air. Not as cold as arctic air masses.
maritime polar (air mass)
An air mass characterized by low temperatures and high humidity.
convergence
An atmospheric condition that exists when the winds cause a horizontal net inflow of air into a specified region.
divergence
An atmospheric condition that exists when the winds cause a horizontal net outflow of air from a specific region.
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.
Pacific air
Cool, moist air that originates over the Pacific Ocean, moves eastward, then descends the Rocky Mountains and moves over the plains as dry, stable, relatively cool air.
Which of the following is NOT correct concerning a warm front?
IT NORMALLY MOVES MORE SLOWLY THAN A COLD FRONT
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.
The Rockies, Sierra Nevada, and Cascades normally protect the _____ from the onslaught of arctic air.
Pacific Northwest
source regions (for air masses)
Regions where air masses originate and acquire their properties of temperature and moisture.
lee-side low
Storm systems (extratropical cyclones) that form on the downwind (lee) side of a mountain chain. In the United States lee-side lows frequently form on the eastern side of the Rockies and Sierra Nevada mountains.
cyclogenesis
The development or strengthening of middle- latitude (extratropical) cyclones.
open wave
The stage of development of a wave cyclone (mid-latitude cyclonic storm) 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.
front
The transition zone between two distinct air masses.
cold advection
The transport of cold air by the wind from a region of lower temperatures to a region of higher temperature.
warm advection
The transport of warm air by the wind from a region of higher temperatures to a region of lower temperatures.
Which below is not a name given to a large cyclonic storm system that forms in the middle latitudes?
antocyclones
Cold fronts that move into the United States from the east, or northeast, are called ____ fronts.
back door
A stationary front does not move because winds on both sides of the front ____.
blow parallel to the front and in opposite directions
One would expect a cP air mass to be ____.
cold and dry
What type of weather front would be responsible for the following weather forecast: "Increasing cloudiness and warm today with the possibility of showers and thunderstorms by this evening. Turning much colder tonight. Winds southwesterly today, becoming gusty and shifting to northwesterly by tonight."
cold front
What type of air mass would be responsible for hot, dry summer weather in southern Arizona?
ct
Which air mass forms over North America only in summer?
ct
Any development or strengthening of a mid-latitude cyclone is called _____.
cyclogenesis
Atmospheric shortwaves tend to ____ when they approach a longwave trough and ____ when they approach a ridge.
deepen; weaken
A front is the transition zone between two air masses of different _____.
directions
Generally, the average speed of a warm front ____ the average speed of a cold front.
is slower than
According to the model of the life cycle of a wave cyclone, the storm system is normally most intense as a(n) ____.
mature cyclone
What type of air mass would be responsible for daily afternoon thunderstorms along the Gulf Coast of the United States?
mt
What type of air mass would be responsible for hot, muggy summer weather in the eastern half of the United States?
mt
In the polar front theory of a developing wave cyclone, the area of most intense weather is normally found to the ____ of the storm's center.
northwest
If a cold front catches up to and overtakes a warm front, the frontal boundary created between the two air masses is called a(n) _____.
occlusion
When two air masses collide at a front, one air mass is pushed upward by the other. This is because...
one air mass is denser than the other
When two air masses collide at a front, one air mass may be pushed upward by the other. This is because ____.
one air mass is denser than the other
Where does the humid, subtropical air that affects much of the weather east of the Rockies originate?
over the Gulf of Mexico and Caribbean Sea
During a cold occlusion, the cold front forces the warm front to ____.
rise off the ground
Drylines typically occur in the ____.
southern Great Plains of the United States
Air masses are usually classified according to their _____.
temperature and humidity
Typically, winter maritime polar air masses along the Atlantic coast of North America are less common than maritime polar air masses along the Pacific coast mainly due to the fact that:
the prevailing winds aloft are westerly
If lows and highs aloft are directly above lows and high at the surface, ____.
the surface system would dissipate
A stationary front does not move because...
the winds blow parallel to the front
For a surface low to develop into a major storm system, _____.
upper-level divergence air must be greater than surface convergence of air
What type of weather front would be responsible for the following weather forecast? "Increasing high cloudiness and cold this morning. Clouds increasing and lowering this afternoon with a chance of snow or rain tonight. Precipitation ending tomorrow morning. Turning much warmer. Winds from the south and becoming southwesterly tomorrow."
warm front
Maritime air masses typically form over ____ and have _____ air.
water; moist
Because the mid-latitude cyclone forms and moves along the polar front in a wavelike manner, the developing storm is referred to as a(n) _____.
wave cyclone
According to the polar front theory of a developing wave cyclone, the storm system is usually most intense:
when the system first becomes occluded
