Meteorology exam #4

An air mass is a large body of air that has homogeneous physical properties (same or similar throughout) such as temperature and moisture content.

An air mass is typically pretty large and it can take days for it to pass over an area. This leads to "air mass weather" when the weather in that area stays pretty consistent as the air mass passes through.

1) Must be an extensive and physically uniform area. 2) Area characterized by a general stagnation of atmospheric circulation so that air will stay over the region long enough to come to some measure of equilibrium with the surface.

Cold and warm air masses clash, often because the converging winds of a traveling cyclone draw the together, means that this region lacks the conditions necessary to be a source region. instead this latitude belt is one of the stormiest on the planet.

Latitude of the source region and the nature of the surface in the area of origin.

They are not listed because they seldom, if ever, form.

k - when an air mass is colder than the surface over which it is passing. w - an air mass is warmer than the underlying surface.

k - often characterized by cumulus clouds, and if precipitation occurs, it will be of the shower or thunderstorm variety. 

w - This condition does not favor the ascent of air, and so it opposes cloud formation and precipitation, if any, will be lighter to moderate.

Mechanical or dynamic modifications of air masses happen due to vertical movements induced by a pressure system or topography. When an air mass is drawn into a low pressure system, for example, convergence and lifting can make the air mass more unstable. The opposite would be true for a high pressure system and the air mass would become more stable. If an air mass is lifted over high topography it can become more unstable, but more stable as it descends topography.

• mT- provides precipitation to United States and warm weather
• cP- lake effect snow

Maritime Polar or Maritime Tropical, depending on where the coastal area is.

Because there are no major barriers to their movement between their source region of high latitude and the Gulf of Mexico. cP and cA air masses can sweep rapidly and with relative ease far southward into the United States.

cP air masses in the winter, periodically, brief heavy snow showers issue from dark clouds that move onshore from the lakes. Seldom do these storms move more than about 80 km inland. These highly localized storms, occurring along the leeward shores of the Great Lakes, create what are known as lake-effect snows.

As in the case for mP air from the Pacific, air masses forming in the northwestern Atlantic source region were originally cP air masses that moved from the continent and were transformed over the ocean. However, unlike air masses from the North Pacific, mP air from the Atlantic only occasionally affects the weather of North America. Only really affect Appalachians

Maritime Tropical air masses through invasion of mT air masses that the Subtropics export much heat and moisture to the cooler and drier areas to the north. Capable of producing significant precipitation

The weather associated with warm fronts is generally much more mild than that associated with cold fronts. Warm fronts usually produce light to moderate precipitation over a large area and for an extended period. After a warm front passes, temperatures gradually rise. Cold front weather is usually more violent than warm front weather with more intense precipitation over a smaller area. Cold fronts often produce severe weather including thunderstorms and tornadoes. A marked temperature drop and wind shift also usually accompanies the passage of cold fronts.

steepness of slope and rate of movement. Cold fronts steepen on the move and twice as fast as warm fronts. They advance faster by 50% more than warm fronts.

Backdoor cold fronts come in from the east or northeast.

Overrunning occurs along stationary fronts.

Dry lines are formed with humidity, Drier air is denser and forcefully lists the moist air in its path much like a cold front.

Low-pressure systems with diameters that often exceed 1000 Kilometers and travel from west to east across the middle latitudes in both hemispheres. Lasting from a few days to more than a week, most have a cold front and a warm front extending from the central area of low pressure.

Develop in conjunction with polar fronts.

The process that produces a new cyclone, also the process that produces an intensification of a preexisting cyclone

Counterclockwise circulation, Convergence of air at the surface

When the warm air is forced aloft the surface pressure gradient weakens as does the storm itself. As the warm air is forced aloft cold air surrounds the cyclone at the surface and the horizontal temperature difference between the two contracting air masses is eliminated and the cyclone has exhausted its source of energy and no longer exists

a cyclone depends on the flow aloft to maintain its circulation with convergence at the surface and divergence aloft and general subsidence of the air column

Speed divergence - a mechanism responsible for divergence aloft is a phenomenon where wind speeds change dramatically in the jet stream, on entering a zone of high wind speed air accelerates and stretches out. Speed convergence is when air enters a zone of slower wind speed, an air pileup results.

United states surface cyclones generally form east of an upper-level trough. The zone in the jet stream that experiences convergence and Anticyclonic rotation is located downstream from a ridge.

The Gulf of Mexico, the Atlantic Ocean east of the Carolinas, Alberta (eastern slopes of Canadian Rockies), Colorado (eastern slopes of U.S. Rockies)

They form in the north pacific, and these low systems provide the winter rainy season that affects much of the west coast but diminish once they hit the rockies

The Mid-Atlantic coast to New England is affected by these storms, winds preceding them from northeast coast and once formed follow the coast.

The motion is rather straight.

Dense frigid air that can bring record breaking temps.

A large anticyclones persist over a region for several days or even weeks. Once in place these stagnant anticyclones block or redirect the migration of midlatitude cyclones. One side dry the other flooded

Dreary weather with large quantities of rain.

It consists of three interacting air streams: two that originate near the surface and ascent and a third that originates in the uppermost troposphere.

Gulf of mexico.

Whereas both the warm and cold belts being at the surface, the dry air originates in the uppermost troposphere.

In south Asia and Australia it is applied to hurricanes. in the great plains it is applied to tornado's. It is also the nick names for athletic teams at Iowa State.

Tornadoes and hurricanes are both smaller and more violent than mid latitude cyclones. A mid latitude cyclone may have a diameter of 1600 kilometers or more. by contrast hurricanes average only 600 kilometers and tornadoes only with a diameter of just 0.25 kilometers.

Since thunderstorms are produced in towering cumulonimbus clouds, a prime requirement is warm, moist, unstable air.

• The topics
• Mid Florida,

Spring, Mid-day.