WEF Flashcards
Drizzle
Always a warm process
Must be 2000ft thick
~(-5C)
Showery Precipitation
Clouds need to be at least 8,000-10,000ft thick
Tops (-12C) - (-20C)
Single Freezing Levels (rain, snow, mixed)
Rain: >1200ft
Snow: <600ft
Mixed: 600-1200ft
Freezing Rain
Top cold layer
Thick warm layer where ice completely melts
Cold layer with supercooled droplets
Surface 0C or less
Eastern side of US
Ahead of warm front and behind cold front
Poleward side of stationary front
Ice Pellets
Cold top layer
Warm shallow layer where droplets partially melt
Cold bottom layer
Slower accumulation rate
Snow
Freezing level is cold throughout
Heaviest snow will have temperatures closest to the freezing level
Heaviest snow fall
Surface low: 0C w/ 0 to(-5C) dew point, N and downstream of Low
700mb: -6C w/ -6 to (-10C) dew point, passage of ridge snow begins
500mb: -35/-25C, heaviest snow after 500 ridge and ends after 500 trof
Vorticity: -24 to -37C
Baroclinic Deep Occluding Low: Blizzard, >40kts/<20F, >50kts/<10F, 1-2 inches lasting 20 hrs
Insulation/Radiation factors
Latitude, seasons, diurnal changes, lapse rate and inversions
Ways to forecast MAX temp
Climatology, Advection upstream, Skew T, CCL, Persistence, Numerical Guidance
How to forecast MIN temperature
Climatology, Skew T, Dew point method, Numerical Guidance
Cold/Heat wave setup
Cold: Trof to E, Ridge to W
Heat: Trof to W, Ridge to E
PA/DA
PA: the altitude which corresponds to a given standard atmospheric pressure
DA: the altitude is the altitude in the standard atmosphere characterized by known air density in the existing atmosphere. Warmer temps - less dense, colder temps - more dense (higher take off speed).
Fog Formation
Stability, cooling, moistures and light mixing
Fog Dissipation
Instability, Heating, Drying out and Increased mixing (winds)
Radiation Fog
Nocturnal event
After rain event (36hrs)
Calm winds, Cool dew points, Clear skies
Does not form over snow
If there is a lack of moisture can be ~2ft
Extremely vulnerable to conditions
Advection Fog
Cold surface/ Warm air (maritime air)
3-9kt winds, deep fog
can extend 150-250nm
Sea fog: Warm moist air over cold water. Can still exists in strong winds if water is 30-40F
Upslope Fog
Air cools adiabatically as it rises upslope at a rate of 5.3F per 1,000ft
Begins as stratus
Great Plains, Appalachians and Rockies
Steam Fog
Unstable, Cold/Warm
2-3ft thigh
Fall, early winter