| Term | Definition |
|---|
| Polar Front Theory | Norwegian model of how middle latitude storms develop (their birth, growth, and decay) connects them to the polar front |
| Polar front | transition zone between cold polar air and warm subtropical air (Ferrel Cell) convergence at the surface and divergence aloft resulting in low surface pressure |
| Central Pressure | junction between two fronts in a frontal wave |
| Life cycle of a middle latitude cyclone | first a stationary front develops with opposing wind directions on either side, so that it separates into a warm and cold front (frontal wave) rotating on a central pressure (low), then the cold front overruns the warm front and creates an open wave which then occludes and becomes a cyclone |
| Frontal Wave | in the life of a middle latitude cyclone, a warm front rotating with a cold front at a central pressure junction due to opposing winds |
| Open Wave | in the life of a middle latitude cyclone, a frontal wave's cold front overruns the warm front creating a warm sector between the two fronts |
| Weather patterns around a cyclonic wave | south of the wave is a warm front with precipitation followed by a dry cold front and a sharp drop in pressure, north of the wave some clouds, no precipitation |
| Triple point | the point where the cold, warm, and occluded fronts come together in an advanced occlusion front of the middle latitude cyclone. At this point, storm dissipates because the warm sector of the open wave is removed and there is cold air on both sides of the front |
| Energy for the middle latitude cyclone comes from | rising warm and moist air provides kinetic energy, and the latent heat of condensation |
| Family of Cyclones | a succession of wave cyclones which are connected |
| Cyclogenesis | development or strengthening of a middle latitude cyclone |
| Lee cyclogenesis | Westerly winds over N-S mountains cause lee-side lows so the wind curves cyclonically which strengthens cyclogenesis |
| Nor'easters | warm moist air from gulf stream increases density contrasts with stationary fronts to cause sudden storms |
| In a middle latitude cyclone, if surface convergence is aligned with divergence aloft... | the storm will dissipate |
| In a middle latitude cyclone, if the surface convergence (divergence) is weaker than divergence (convergence) aloft... | the storm intensifies |
| Longwaves | uneven heating and rotation of the planet cause long wavelengths that are slow or stationary |
| Shortwaves | Embedded in longwaves, travel faster and intensify troughs of longwaves |
| Vertical Structure of a Middle Latitude Cyclone | Surface low, divergence aloft aligned to surface low, the low aloft is west of the surface low |
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