1. frontal wave ("kink" in polar front) (animation)
2. open wave = fully developed w/warm sector
3. triple point -- secondary low
4. energy source(s) for storm
   • kinetic energy
     • cold air sinks / warm air rises
     • surface convergence = wind acceleration
   • latent heat (of condensation)
5. storm energy - tremendous!

1. definition:
   development or strengthening of storms
2. favored locations
   • Rocky Mtns
   • Gulf of Mexico
   • Atlantic
   • Great Basin
3. keys
   • lift!
   • upper wind flow (determined by wx balloon)
4. divergence/convergence relationship
   ... second diagram
   • divergence aloft
     • lower density
     • lower surface pressure
     • = lift = storm
   • convergence aloft
     • higher density
     • higher surface pressure
     • = no lift = kills surface storm
5. stacked vs. tilted storms
   • stacked
     • convergence aloft (no lift)
     • subsidence
     • kills surface storm
   • tilted
     • divergence aloft (lift)
     • good "exhaust"
     • lower level convergence
6. storm movement
   • follow 500mb flow
   • speed = 1/2 500mb flow speed
   • faster in winter

A. Longwaves (Rossby Waves)

1. troughs and ridges
2. typically 4-6 in N hemisphere
3. wavelength = 2400-5000 miles
4. move ~4° long. per day
5. seasonal drift north-south

1. disturbance embedded in longwave
2. faster movement
3. approx. speed of 700mb flow
4. can deepen longwave trough and strengthen themselves

D. General Terminology

1. barotropic conditions
   • height contours parallel isotherms
2. baroclinic conditions
   • pressure contours cross isotherms
   • cold / warm advection
     = increase in temperature contrast
     = strengthens storm
   • baroclinic = instability
3. cut-off low
   vs. closed low & split flow
4. comma clouds
   ... another example
5. jet maximum or jet streak
   = upper divergence

1. related to divergence aloft (see I.B.4. above)
   • strong divergence aloft = strong updrafts
   • = increases spin = surface vorticity
2. positive vorticity
   • cyclonic (counterclockwise)
3. planetary vorticity
   • vorticity due to spin of earth
   • min = equator; max = poles
4. relative vorticity
   • curvature of flow + diff. wind speeds
   • diff. in speed = shear = vorticity
5. absolute vorticity = planetary + relative
6. "vort max"

STORMS CHAPTERS ----->

Air Mass / Fronts

Midlatitude Cyclone

Thunderstorms

Hurricanes