Weather Flashcards
Dew point
Air can’t hold any more moisture, saturated and begins to condensate
When water in air becomes visible as moisture, cloud, fog
Current temp more than 3 degrees from dew point to be safe
Atmosphere layers
Troposphere, up to 48k ft Tropopause layer with Jetstream Stratosphere Mesosphere Thermosphere
Atmospheric circulation
Warm air rises at equator, moves up to poles, back down to equator
Atmospheric pressure
Decreases at one inch per 1000ft
Coriolis forces
Due to rotation of the earth
Northern hemisphere deflecting air to the right,eastward
Northeasterly trade winds from 30• to equator
Measuring atmospheric pressure
Aneroid vs mercurial barometer
Weather station pressure convertered to sea level, adding 1” Hg for every 1000ft
Currents and winds
Due to pressure differences, coriolis, friction, temperature differences
Upward, downward, horizontal
Cause weather changes
Cyclonic vs anti cyclonic circulation
Northern hemisphere high pressure deflection to the right clockwise pattern
Low pressure counterclockwise
High vs low pressure
High, descending dry air, good weather
Low, air flows into area to replace rising air, brings clouds, rain
Convective currents
Local circulation of air due to uneven heating of the ground, turbulence
Water, vegetation hearts slower
Low level wind shear
Dangerous
Due to passing frontal system, thunderstorms, temperature inversion, strong upper level wind
Microbursts
Servere type of low level wind shear Intense rain at the surface At cloud base ring of blowing dust 1-2 miles diameter, depth of 1000ft 5-15min, downdrafts of up to 6000ft/min
Weather station symbols
Circle = station
Line points into direction where wind is coming from
Speed = barbs and pennants, 5, 10, 50
Isobars
Lines of equal pressure in mb
Close together = steep gradient, strong winds
Ridge = elongated area of high pressure
Trough = elongated area of low pressure
Adiabatic process
Heating and cooling off air when rising vs descending, temp lowers as air rises and expands
Moist air cools slower, rises higher, unstable
Inversion
Cool air below warmer air, at night, cool surface cools down few hundred feet of air, capped by top of layer
How air can reach saturation point
- Warm air moves over cold surface
- Cold and warm air mix
- Air cools at night contact with cooler ground
- Air forced into high atmosphere
Radiation vs advection fog
Ground cools rapidly, in valleys, air reaches dew point, vs
Wind pushes most warm air over cool surface, coastal fog
Uplope vs steam vs ice fog
Wind pushes moist air up mountain range
Cold dry air moves over warm water causing water to evaporate
In arctic region, water vapor into ice
Clouds
Air cools, reaches saturation point, deposition, sublimation, condensation, onto condensation nuclei (dust, salt, smoke)
Low - base up to 6500ft AGL
Middle - 6500-20k
High - above 20k
Cloud classification
Cumulus Stratus Cirrus Castellanus Lenticularus Nimbus Fracto Alto
Ceiling
Lowest level of clouds reported as broken or overcast
Broken: 5/8 to 7/8 of sky covered
Overcast = 100% covered
Cumulus clouds
Extensive vertical development
Base is low, extend high altitude
Instability, turbulence, thunderstorms
Lightning, hail, tornadoes, gusty, wind shear
Precipitation
Drizzle, very small water droplets, fog
Virga, rain that evaporates before reaching the ground
Rain falling through temperature inversion may freeze, ice pellets
Air masses
Based on source region
Take on surrounding characteristics
Polar, tropical, dry deserts
Moves over cold or warm land
Front
Boundary layer between 2 air masses, chances in weather imminent
Warm, cold, stationary, occluded
Warm front
Slow moving, moves over cooler air, pushes it out, high humidity, fog, rain, thunderstorms when warm air is lifted, barometric pressure falling
Stratiform clouds, cumulonimbus in summer
Cold front
Move rapidly, close to ground, forcing warm air up, forming clouds
Cirriform, cumulus clouds, rain showers
Can produce tornadoes, poor visibility, gusty winds, temperature and dew point dropping
Occluded front
Fast cold front catches up with slow warm front
Cold front occlusion, mixture of weather
Warm front occlusion, thunderstorms
Thunderstorm conditions
Air with sufficient water vapor, unstable lapse rate, initial lifting action
Air mass storms (short) versus steady state storms (long)
Squall line
Narrow band of thunderstorms, ahead of cold front, moist unstable air, wide and long, forms rapidly
Tornado
Thunderstorm draw air into cloud with rotation, concentrated, 200kts winds, low pressure inside vortex, tornado of cloud touches ground, or waterspout, if water
Thundering hazards
Turbulence Icing Hail Ceiling and visibility Lightning Pressure Engine water ingestion
