METEOROLOGY. GEL-1370. Chapter Eight. Air Masses, Fronts, and Middle-Latitude Cyclones. Goal for this Chapter. We are going to learn answers to the following questions: What are the different types of air masses? How fronts are formed?
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Air Masses, Fronts, and Middle-Latitude Cyclones
We are going to learn answers to the following questions:
Air Masses of North Americal
Continental Polar (cP) & continental Arctic (cA): Bitterly cold weather enters US in the winter; originate over ice- and snow-covered regions of northern Canada and Alaska; the air in contact with the surface becomes very cold and stable with little moisture; portion of this air breaks away and moves southward as a shallow high pressure area
A winter upper-air pattern that brings mP air into the west coast of North America; large arrow: the upper-level flow; small arrows: trajectory of the mP air at the surface
Weather condition during a hot spell on 17 April, 1976; Red: maximum temp.; blue: minimum reached; heavy arrow: average upper-level flow; L & H: average position of the upper-level trough & ridge
cT air covered a large area of the central and western US during 29,30th June, 1990; #: maximum temp (°F); H shows with the isobar shows the upper level position of the subtropical high; winds aloft are weak
Formation of a Lake-Effect Snow; cold, dry air crossing the lake gains moisture & warmth from the water; buoyant air rises and cloud forms leading to snowfall
Surface weather associated with a cold front in the southeastern US; temperature (top), dew point (bottom), present weather, cloud cover, sea level pressure (/:rising;\), wind speed & direction
Tropical weather conditions associated with a warm front warm front along a line P-P’ – horizontal / vertical ~150-200.
Idealized life cycle of a wave cyclone in the Northern Hemisphere based on Polar Front Theory; Arrow next L shows direction of storm movement
Convergence, divergence, and vertical motions associated with surface pressure systems; for the surface storm to intensify, upper trough of low pressure must be located to the left (or west) of the surface low