Weather Flashcards
Reference pubs
AIM
FIH
Atmosphere composition
78% Nitrogen
21% Oxygen
1% other
Troposphere
-Adjacent to surface (28k-55k AGL) (36k’ US)
-temp dec w altitude
-winds inc w altitude
-nearly all weather occurs here
Pressure
Ambient static pressure is measured by weight of a column of air above Earth’s surface
Always dec w altitude
2 units for pressure
- Inches of Mercury (“ Hg)
- millibars (mb)
Standard pressure lapse rate
1” Hg lost per 1,000 ft alt
Pressure gradient force
As pressure is exerted on Earth’s surface it moves outward in either ascending or descending manner
Air moves from areas of high pressure to low pressure
PGF (high pressure)
Descending air
PGF (low pressure)
Ascending air
How far are isobars separated
4 mb pressure
Standards at sea level
29.92” Hg
15 C (59 F)
Temp lapse rate
2 C/1,000 ‘
Sea level pressure
SLP is the pressure read directly at sea level or calculated from known station pressure
Station pressure
SP is atmospheric pressure read directly at an airfield or specific altitude
Will always be less than equivalent sea level pressure when station is above sea level
SLP= SP+FE
Types of altitudes
Indicated
True (MSL)
Absolute (AGL)
Density
Pressure
Indicated altitude
Simply what altitude indicates
True altitude (MSL)
Height above mean sea level. This is standard altitude used
Absolute altitude (AGL)
Height above terrain below you
Density altitude
Not displayed on altimeter, calculated to determine the altitude the airplane “thinks” it’s at. Used for performance purposes
Pressure altitude
Altitude displayed when 29.92 is set in the Kollsman window (standard altitude setting in class A airspace 18k ft and above)
What does the altimeter measure
Measures the difference between the static pressure and pressure set in Kollsman window
Calibrated for 1,000 ft change for every 1” Hg diff
Indicated altitude will never match the true altitude whenever the setting in the Kollsman window is incorrect
How does pressure changes affect the altimeter
Change in pressure of 1” Hg will change the altimeter by 1,000 ft
Important to update altimeter settings throughout flight
“High to low - look out below”
“Low to high - plenty of sky”
High to low
MSL = assigned alt (-) alt error
AGL = MSL (-) field elevation
Indicated alt on deck = field elevation (+) alt error
Low to high
MSL = assigned alt (+) alt error
AGL = MSL (-) field elevation
Indicated alt on deck = field elevation (-) alt error
Effects of temp deviations on altimeters
If colder than standard atmosphere, altitude will indicate higher altitude
If warmer than standard atmosphere, alt will indicate lower alt
Air masses
Large body of air with relatively same temp and moisture across a horizontal plane
Named for temp relative to surface
Temp, location, moisture for naming
What causes circulation and how does it affect the air
Constant heating and cooling of the Earth’s surface leads to ascending and descending air
Dew point
Amount of moisture in air
Air is saturated when temp = dew point
Cold air holds less moisture
Dew point spread
As spread dec, moisture will begin to condense and become visible
Visible moisture forms frost, fog, clouds
Effects of temp deviations on altimeters
If colder than standard atmosphere, altimeter will indicate higher altitude (MSL lower)
If warmer than standard atmosphere, altimeter will indicate lower altitude (MSL higher)
What’s an air mass and what’re they named for
Large body of air w relatively same temp and moisture across a horizontal plane
Named for temp relative to surface,
temp, location, moisture for naming
Stability vs type of air mass
Cold air mass = unstable
Warm air mass = stable
What is weather the result of
Heat exchange
Compounded by spinning of earth (Coriolis effect)
What is relative humidity
Relative humidity is not direct measurement of the actual amount of water vapor/moisture, only the actual amount in the air compared to the amount that could be present if saturated
The closer you get to 100% more likely you’ll see visible moisture
Warmer air can hold more moisture than cold air
What are two key elements in pre flight planning
Temperature and dewpoint
Temperature inversion
Temperature normally decreases as you gain altitude. However sometimes temperature can increase as you gain altitude
What is pressure gradient force
Driving force of all wind
Descending air result in high pressure and flows outward away from high-pressure center
Ascending air result in low pressure and flows inward toward the low pressure center
“Out of the highs and into the lows”
Winds don’t travel the same direction pressure does due to Coriolis effect
What are gradient winds
Found above 2000 AGL and flow parallel to how the isobars are depicted on a surface chart
Clockwise around high-pressure centers
Counter clockwise around low pressure centers
What are surface winds
Heavily influenced by surface friction and found below 2000 AGL
Do not flow exactly parallel to the isobars due to surface friction
Surface winds around low pressure center will tend to turn towards center
Surface winds around high pressure center tend to turn away from center
What is a jet stream
Average height is 30,000 feet
generally flows west to east
Average speed is 100 to 150 kts
100 to 400 miles wide
1000 to 3000 miles long
3000 to 7000 feet thick
What is Seabreeze
Cool dense air over water moves over warm land during day
Air warms rises and returns over ocean
Usually 1500 feet to 3000 feet AGL and 15 to 20 kts
What is land breeze
Land cools faster than water so now water is warmer causing the cycle to reverse as result
What’s a front
Discontinuity between contrasting air masses
 specific discontinuities used to locate  classify fronts are:
Temperature, dew point, wind, pressure
“Touch downs win playoffs”
What is a cold front
Colder, more dense air moves into warm air (bulldozer)
Cool air slide underneath forcing warm air up
results in unstable conditions, cumuliform clouds, showery precipitation
What is the squall line
Line of fast-moving thunderstorms
Often develop 50 to 30 miles in front of cold fronts
Contain severe hazards to aviation
Warm front
Warm air overtakes cooler air, usually slower
Results in stable condition prior to passage, stratiform clouds, little to no turbulence, continuous precipitation
Stationary front
Alternating cold/warm front symbols pointing in opposite direction
Can align any direction
Weather conditions similar to that of warm front, but often less intense
Occluded front
Cold front overtakes warm front
Wind shifts 180° from south east to north west
Weather associated with both warm/cold fronts over wide areas
What determines stability
Temperature of the surrounding air

Stable
Colder air settles when lifting action removed
Unstable
Warmer air continues to rise
Neutrally stable
Same temperature air simply remains at point where lifting action was removed
Cloud types
Stratiform
Cumuliform
Stratiform clouds
Comes from moist stable air and associated with steady precipitation
Widespread with no definable shape
Cumuliform clouds
Comes from moist unstable air and associated with showery precipitation
Large puffy clouds with more definite shapes and vertical development
Precipitation characteristics
Showery: Sudden start and stop, abrupt intensity changes, cumuliform type clouds
Continuous: with gradual change, Stratiform clouds
Intermittent: Starts/Stops at least once during the hour, either type cloud
Special clouds (Extensive vertical development)
Nimbo/Nimbus: Violent or heavy
Cumulonimbus (thunderstorms):
Severe to extreme turbulence, hail, icing, lightning, bases at low altitude, tops at high altitudes
Nimbostratus:
Thick, uniform, widespread clouds that build downwards. Heavy rain showers and moderate turbulence, no thunder
What are the three cloud groups
Low, middle, high
Low cloud group
SFC – 6500 feet AGL
No prefix
Stratus/cumulus
Middle cloud group
6500 feet AGL to 20,000 feet AGL
“Alto”
Altostratus/altocumulus
High cloud group
> 20,000 feet AGL
“Cirro” zero chance icing
Cirrostratus/cirrocumulus

What are the four lifting methods
Frontal
Orographic
Convergence
Thermal
Frontal lifting
Only deals with cold fronts fronts
Orographic lifting
Anything on ground lifting air
Ex. Mountains and hills
Convergence lifting
Air flowing hitting other air masses
Thermal lifting
Warm air rising up
Flight conditions: F.A.T V.IP Wants Chow
Fronts
Air mass
Turbulence
Visibility
Icing
Precipitation
Winds
Cloud types
What Would Sarah Palin Repeat, Something Silly Stupid
“Stable atm conditions”
Warm
Warm
Smooth
Poor
Rime
Steady
Steady
Stratus
Captain Crunch Really Good Cereal Super Good Cereal
“Unstable atm conditions”
Cold
Cold
Rough
Good, Outside of clouds
Clear
Showery
Gusty
Cumulus
Turbulence
Irregular or disturbed atmospheric flow producing gust and or eddies
Most hazardous at low altitude
Intensity classification for hazards
Light
Moderate
Severe
Extreme ( declare emergency, exit area asap or you gonna die)
Reporting duration of turbulence
Occasional (Less than 1/3 of the time)
Intermittent (1/3 to 2/3 of the time)
Continuous (More than 2/3 of the time)
What are the different types of turbulence
Thermal
Mechanical
Frontal
Large scale wind shear
Thermal turbulence
Results from the heating below
Strength depends on the type of surface being heated
Mechanical turbulence
When buildings or ground objects interfere with normal wind flow; Usually no more than 1000 feet AGL
Can occur with hills/valleys
Depends on the speed of the wind, roughness of terrain, instability of air
Frontal turbulence
The result of frontal lifting that is associated with the passage of a cold front
Most prominent in fast-moving cold fronts
Little to no lifting associated with warm front, therefore no frontal turbulence associated with warm fronts
Wind shear turbulence
Sudden, drastic change in windshear and or direction that can occur anywhere
High level – associated with clear air turbulence like jetstream
Low level – “LLWS” (Most dangerous) due to local phenomenon such as a temperature inversion (temp inversion near surface can cause wind shear)
How to penetrate turbulence
(Don’t chase airspeed/altitude and maintain good attitude)
- Maintain power setting consistent w aircraft’s recommended airspeed for turbulence penetration
- Trim aircraft for level flight
- Do not chase airspeeds or altitude variations
- Maintain pitch and bank (good attitude) VFR scan when conditions permit
What are the requirements for icing
Visible moisture, free air temperature below freezing
What are the three kinds of ice
Clear ice
Rime ice
Mixed ice
What is clear ice
0°C to -10°C (unstable conditions)
Freezing rain, large droplets, cumulus clouds, most severe, difficult to remove
Freezes slowly after spreading out and altering the shape of the wing
What is rime ice
Stratus clouds, tiny droplets that freeze instantly
What is Mixed ice
-8°C to -15°C
Combo of two
Most common icing
What are the 3 kinds of icing
Structural icing
Engine icing
Ground icing
What is structural icing
Most hazardous aspect is aero effect on airfoils, changes shape
What is engine icing (2 types)
Compressor
- Can cause imbalance on compressor vanes
-Result in ice ingestion, resulting in FOD Hazard
Induction
-Results in restricted airflow into inlet, flameout
-Can occur in a high humidity at times up to +10°C
Reporting (PIREDs)
“I Want RUM”
I: conditions on IFR approach differ from the latest observation
W: Wind shear encountered on T/O or LDNG
R: when Requested
U: when Unusual/Unforecasted conditions encountered
M: Missed approach
Ground icing
Frost
- occurs on ground and you shall remove prior to flight
-no scraping the windshield
You need clear night, no wind, dew point below freezing

What could happen when taxiing through water
The water could quickly freeze as you gain altitude
Effects on breaking action on runway
May have to extend landing roll out
Do not fly in icing conditions
What is visibility
Ability to see prominent unlighted objects during day and prominent lighted objects at night
Types of visibility phenomena
Reported obscured when visibility reduced to less than 7 miles
Fog
Haze
Smoke
Rain and drizzle
Snow
Blowing snow, dust, sand
What is fog and what’re the 2 types
Cloud base within 50 feet of ground
Greater than 20 feet thick
Reduces visibility to less than 5/8 of a mile
radiation
-Nocturnal cooling and sun will dissipate it
Advection
-Cooling of a moving air mass and too thick for sun to penetrate
What is the thunderstorm lifecycle
Developing stage
Mature stage (where most hazards occur)
Dissipating stage

What are the thunderstorm hazards
”HI MELT”
Hail
Icing
Microbursts
Extreme turbulence
Lightning
Tornadoes
What’s a gust front
Dangerous gusty winds that occur 5 to 20 miles in front of an approaching thunderstorm. Never take off or land when thunder storm is approaching
What is hail
May be carried 10 to 20 miles downwind and in clear air
Can cause severe damage in seconds
What are microburst
Severe, localized downdraft 2000 to 6000 ft./min.
Producing vortex ring of wind 20 to 200 kts
Severe hazard on takeoff and landing
Usually 5 to 10 minutes, very localized
Taking off into microburst
IAS rapidly increases due to massive headwind
Natural reaction is to reduce throttle
Loss of airspeed on other side due to massive tailwind
Lightning
Can strike in clear air outside thunderstorm
Flash blindness may occur
Generally not serious when in aircraft
Thunderstorm avoidance recommendations (in this order)
Circumnavigate (fly around)
Fly over (1000ft per 10kt wind at top)
Fly under
Fly though (penetrate the lower 1/3 of the storm 4000’-6000’ AGL as the upper 2/3 is most likely to encounter hail and/or icing
Flight visibility
Ability to see and identify prominent unlighted objects during day and prominent lighted objects at night
Prevailing visibility
Greatest horizontal visibility throughout at least half of the horizon circle
Slant visibility
Distance on final when the runway environment is in sight
Runway visual range (RVR)
Horizontal distance looking down the runway
Sky coverage is reported in _____
Eights (as you look up)
Height of cloud base given in hundreds of ft AGL
Ceiling
Lowest broken or overcast layer
May be other clouds of layers above
Vertical visibility (VV)
Distance seen directly upward from the ground into a total obstruction
Used when sky is totally hidden
Hazardous and greatly affects the slant range visibility
Referred to as an “indefinite ceiling”
Describe use of PIREPS (Pilot reports)
“I Want RUM”
I: conditions on IFR approach differ from latest observation
W: Wind shear
R: when Requested
U: when Unusual/Unforecasted conditions are encountered
M: Missed approach
Also report:
Cloud bases, tops, layers
Flight visibility
Precipitation
Visibility restrictions
Winds at altitude
Temperatures aloft
