Extratropical Cyclones Flashcards
Winds follow
Isobars
Winter polar continental
Cold and dry
Summer polar continental
Warm and dry
Conditions associated with winter polar continental
Sno
Tropical continental
Hot and dry, low visbility
Polar maritime
Cool and moist
Returning polar maritime
Mix between polar and tropical maritime conditions
Arctic maritime
Cold and dry, can lead to snow and hail
Three wind cells
Hadley, Ferrel, polar
Hadley cell - Hadley cell
Convergence
Ferrel cell - Hadley cell
Divergence
Polar cell - Ferrel cell
Convergence
Diverging air produces
High pressure
Polar jet stream is associated with
Ferrel cell and polar cell
Subtropical jet occurs between
Ferrel cell and Hadley cell
Thermal wind relation
Pressure decreases with height quicker in cold air
Vertical wind gradient is proportional to the
Horizontal temperature gradient
Undercutting of polar air under subtropical air makes the jet stream
Narrower
The jet stream is stronger in the
Winter hemisphere
Small waves on jet stream can amplify, thus it is
Baroclinically unstable
Perturbations to the jet stream (causing Rossby waves)
Mountains, uneven heating
Extratropical cyclone stage 1
Upper level disturbance causes divergence aloft, low pressure system. Rotation develops around the low.
Convergence in the low promotes
Air to rise
Extratropical cyclone stage 2
Northerly air pushes cold front forward
Extratropical cyclone stage 3
Warm air pushed above the warm front, cold front catches up
Extratropical cyclone stage 4
Cold front overtakes, forming occluded front. Begins at centre and expands out. Inflowing air weakens low, dissipates system
In extratropical cyclones, the low pressures can become
Stacked
The precipitation in ET cyclone is focused at the
Occlusion
Occlusion can form from the
Isothermal wrapping
