polar front theory
the theory postulated in the early 20th century describing the formation, development and dissipation of midlatitude cyclones. Many of the features of the theory are still valid today.
the beginning of cyclone formation with the disruption of the linear frontal boundary between a warm and cold front
With this type, strong storms exist along the cold front. Also, during occlusion of this type, the faster moving cold front catches the slower moving warm front and cold wair forces the warmer air up.
represents the end of the cyclone's life cycle
large, alternating troughs and ridges that establish patterns of upper-level divergence and convergence
rotation of a fluid
the overall rotation of the air and has two components: relative and Earth vorticity (both complement each other and increase the total)
vorticity relative to Earth's surface, depends on air motions with respect to Earth's surface-2 sources: shear and curvature of the flow
vorticity due to Earth's daily rotation about its axis, is a function solely of latitude higher the latitude, the greater the vorticity
surface low-pressure systems resulting from upper-tropospheric motions, typically exist beneath regions of decreasing vorticity in the upper atmosphere, associated with low pressure aloft
caused by localized heating of the air from below, associated with high pressure aloft
the spreading of air due to increasing wind speed in the downwind direction
diffluence and confluences
a type of horizontal divergence that occurs when steamlines spread apart in the downstream direction
smaller ripples superimposed on the larger Rossby waves. They migrate downwind within the Rossby waves and exert their own impact on the life cycle of midlatitude cyclones. They can either enhance or reduce the local divergence or convergence.
the horizontal transport of warm or cold air by the wind, formation of short waves depends on this
warm air advection
the horizontal movement of relatively warm air, where this occurs air is warmer and more buoyant than the air ahead of it and rises, air turns slightly to the right
cold air advection
the horizontal movement of relatively cold air, typically occurs behind a cold front thereby enhancing the temp contrast found on either side of the front, air turns slightly to the left
when the height contours and isotherms are in alignment the atmosphere is considered this
when the height contours and isotherms intersect the atmosphere is considered this
warm and cold air advection causes vertical motions called this
an upper-level area of low pressure that takes on a circular flow distinct from the general flow around it
conveyor belt model
the modern description of air flow through midlatitude cyclones, depicts cyclones in terms of three major flows
Why can storms move in a different direction than the direction the wind is moving?
B/c of the counterclockwise spiral within the midlatitude cyclone. Regardless of the direction in which a system is moving, winds at different points within midlatitude cyclone flow in different directions.
counterclockwise rotation in the Northern Hemisphere
air rotating clockwise
occurs when the speed of a fluid varies across the direction of flow
compaction of air due to decreasing wind speed in the downwind direction
warm conveyor belt
originates near the surface in the warm sector and flows toward and over the wedge of the warm front, the air rises and turns anticyclonically, also associated with the could cover.
cold conveyor belt
lies ahead of the warm front, enters the storm at low levels, air rises and turns anticlyclonically, it gains moisture from evaporation
dry conveyor belt
originates in upper troposphere as part of the generally westerly flow, brings the coldest air into the cyclone, it separates the cloud bands from the warm and cold conveyor belts giving them their comma shaped appearance
as much influences by upper-level conditions as are cyclones, they bring clear skies and calm conditions b/c the cool air wihtin them slowly sinks toward the surface