Weather Flashcards
(110 cards)
1
Q
Standard temp lapse rate
A
2C (3.5F) per 1,000’
2
Q
Units used to measure atmospheric pressure
A
- Inches of mercury (inHg // 29.92)
- Millibars (mB // 1013.2)
3
Q
Standard Day temperature
A
15C or 59F
4
Q
Standard pressure lapse rate
A
1 inHg (34 mb) per 1,000’
5
Q
Where is the abrupt change in the temperature lapse rate?
A
Tropopause
6
Q
Where do jet streams occur?
A
- Just below the tropopause
Average height: 30,000’ MSL
7
Q
Indicated Altitude
A
Altitude read directly from the altimeter
8
Q
True Altitude
A
Actual height above mean sea level (MSL)
9
Q
Absolute altitude
A
Height above the surface (AGL)
10
Q
Density Altitude
A
The pressure altitude corrected for nonstandard temperature
Not actual height, measures a/c performance
11
Q
What happens when pressure goes from high to low?
A
You are lower than you think you are
12
Q
What happens when pressure goes from low to high?
A
You are higher than the altimeter reads
13
Q
You leave your plane at KDLF when your altimeter setting is 30.70. You come back a day later and your altimeter is 29.70. What will your altimeter read?
A
1,000’ higher
14
Q
When you left your a/c, your altimeter was 30.02 and reads 1,080. The next day, the altimeter is 29.02. What will the altimeter read now?
A
2,080
15
Q
If the outside air temperature is colder than the standard temperature you are ___________ than the altimeter reads
A
Lower
16
Q
If the outside air temperature is hotter than the standard temperature you are __________ than the altimeter reads
A
Higher
17
Q
Stations models show wind coming from _______ ________.
A
True North
18
Q
ATIS/Tower/RSU tells winds from _____________ _______.
A
Magnetic North
19
Q
Pressure altitude
A
Height above the standard datum plane when 29.92 is set in the altimeter
20
Q
Direction of rotation for LOW pressure system
A
Counterclockwise
21
Q
Direction of rotation for HIGH pressure system
A
Clockwise
22
Q
What is the pressure gradient force (PGF)?
A
The initiating FORCE for all winds
23
Q
How do gradient winds flow?
A
Parallel to the isobars
24
Q
What does the Coriolis Effect do?
A
- Diverts air to the right w/ respect to its initial direction
- In the Northern hemisphere, winds are deflected to the right by the Coriolis effect
25
Define Land Breeze, how is it created?
Movement of air from land to sea at night
- Created when cooler, denser air from the land forces up warmer air over the sea
26
Define sea breeze, how is it created?
Movement of air from sea to land during the day
- Cooler air from above the water moves over the land, forcing the heated, less dense air above the land to rise
27
What is dew point temperature?
The temperature at which saturation occurs
28
What is the dew point spread?
Difference between air temperature and dew point
29
What is the dew point spread an indicator of?
Moisture in the air
30
What is the result of the dew point and temperature being close together?
Poor visibility (fog)
31
What are the three characteristics of precipitation?
1. Showers
2. Continuous
3. Intermittent
32
Define intermittent precipitation
Stops and starts at least once during the hour
33
Define showers/showery precipitation
Starts, stops, changes intensity or sky conditions rapidly
34
Define continuous precipitation
Steady and changes intensity gradually
35
What are the three levels of clouds, their prefixes, and altitude they form?
1. Low, no prefix, surface - 6500’
2. Middle, alto, 6500’-20,000’
3. High, cirro/cirrus, 20,000’-40,000’
36
Precipitation resulting from cumulus clouds
Showers
37
Precipitation resulting from cumulonimbus clouds
Heavy showers
38
Precipitation resulting from nimbostratus clouds
Heavy and STEADY
39
Precipitation resulting from stratus clouds
Continuous, steady rain
40
What causes an unstable atmosphere?
When lifted air is warmer
41
What causes a stable atmosphere?
When lifted air is colder
42
What causes a neutrally stable atmosphere?
When lifted air is the same temperature
43
Six flight conditions for a stable atmosphere
1. Stratus clouds
2. Smooth flying
3. Poor visibility
4. Steady winds
5. Steady precipitation
6. Rime (icing)
44
Six flight conditions for an unstable atmosphere
1. Cumulus clouds
2. Rough turbulence
3. Good visibility
4. Gusty winds
5. Showery rain
6. Clear icing
45
How can you tell if the air is saturated?
Dew point and temperature are the same
46
Precipitation resulting from stratiform clouds
STEADY, continuous precipitation
47
Air masses can be measured by _____________ and _____ __________.
Temperature // dew point
48
Where are fronts located?
Troughs of low pressure
49
What happens in a trough of low pressure?
1. Pressure FALLS, as the front approaches
2. Pressure then RISES, as the front passes
50
What is a squall line, how is it indicated, and where does it develop?
- Line of violent thunderstorms
- Indicated by dashed, double dotted purple line on surface charts
- Develop 50-300 miles ahead of a cold front
51
What are signs of a warm front?
- Reduced visibility
- Steady precipitation (stratiform clouds)
- Cloudiness
- Wind shift from SE to SW
52
What are signs of a stationary front?
- 180* wind shift
-Similar to warm front, less intense
- Warm lifted air surrounded by cold air = unstable conditions
53
What are signs of an occluded front?
- Stratus clouds and cumulus clouds together
- Likelihood of mixed icing
- Most severe weather is 100 miles SOUTH, and 300 miles NORTH
54
What are the four categories of turbulence?
1. Light
2. Moderate
3. Severe
4. Extreme
55
What are the three turbulence durations?
1. Occasional = Less than 1/3 of the time
2. Intermittent = between 1/3 and 2/3 of the time
3. Continuous = More than 2/3 of the time
56
Jet stream wind shear
Rapid change of wind speed short distance from core
- Vertical shear more significant
57
What are mountain waves?
Strong winds blowing perpendicular to a mountain range
58
What are characteristics of mountain waves?
1. Forms standing waves
2. Turbulence can be in clear air as well as in clouds
3. Clouds are the best way to determine turbulence
4. ROTOR clouds are associated with mountain wave turbulence
59
What should you do to avoid mountain waves?
1. Circumnavigate
2. Fly 50% higher than the peak
3. Approach range at 45* angle
60
A change in 1inHG results in ______ ft change in altimeter reading
1,000’
61
What are rotor clouds?
Form downwind from and parallel to mountain range
62
What are some characteristics of surface winds?
- Below 2000’ AGL
- Friction reduces the speed of the wind which reduces coriolis force
- Blows at 45* angle across isobars from high to low pressure
63
The dew point can never be _______ than the air temperature, only _______ ___ or _________.
Higher; equal to; less
64
What is mechanical turbulence caused by?
Caused by passage of wind over obstructions (buildings, irregular terrain/mountains)
65
Strength and magnitude of mechanical wind shear is determined by?
1. Roughness of terrain
2. Speed of wind
3. Stability of air
66
Define wind shear
Sudden change in wind speed or direction over short distance, vertically or horizontally
67
What are the two types of engine icing?
Compressor and induction icing
68
Icing Requirements
1. Visible moisture
2. Super cooled water droplets
3. Air temperature and aircraft’s surface below freezing
69
Clear icing characteristics
- Found in cumulus clouds, between 0* and -10* Celsius
70
Rime icing characteristics
- Found in stratiform clouds, stable conditions
- Between -10* and -20*C
71
Mixed icing characteristics
- Combo of clear and rime icing, most common
- Between -8 and -15* C
72
Frost characteristics
- Little or no wind allows moisture to deposit as ice crystals
Disrupts boundary flow separation
73
Icing intensities
1. Trace
2. Light
3. Moderate
4. Sever
74
Moderate icing characteristics
- Short encounters become potentially hazardous
- Use of driving/anti-icing equipment or diversion is necessary
75
Aerodynamic effects of icing
Alters shape of airfoil, changing the stall AOA and speed
76
Induction and compressor icing
Both restrict airflow and could FOD engine
77
Options when encountering icing
1. Climb to colder conditions to sublimate or descend to warmer conditions
2. Climb out of visible moisture
78
Minimizing icing effects
- Avoid areas of known or forecasted icing
- Avoid clouds and precipitation between 0*C and -20*C
- Minimize bank angle and high AOA
79
Prevailing visibility is…
- Greatest horizontal visibility
- Equaled or exceeded throughout over half the horizon circle
80
Slant range
Distance on final approach at which runway environment in sight
- PIREP
- Indicates when “break out will happen
81
Runway visual range (RVR)
Horizontal distance seen by looking down runway from approach end (specified point on centerline)
- Reported if visibility less than 1SM or 6000’ PV
82
Visibility is reported in _________.
Eighths
83
A ceiling is the height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported at least ______ and not classified thing or partial as determined by summation principle
5/8
84
Scattered (SCT) visibility
3/8-4/8 (NOT A CEILING)
85
Broken (BRKN) visibility
5/8-7/8
86
Overcast (OVC) visibility
8/8
87
Vertical visibility (VV) definition
Distance seen directly upward from the ground into a total obscuration
88
Partial obscuration definition
NOT a ceiling
89
What is radiation fog caused by?
Radiational cooling of the earth’s surface (at night and over land)
90
Advection fog occurs when…
Warm, moist air moves over cool surface
91
What are the impacts of volcanic ash?
- Engine malfunctions
- Pitted windscreens
- Sandblasting of external surfaces
- NOT turbulence
92
Indications of volcanic ash
- Torching (flames) from engine tailpipe
- St. Elmo’s fire (crazy static electricity shit)
- Bright glow in engine inlets
93
Thunderstorm requirements
1. Moisture
2. Unstable air
3. Lifting action
94
Gust fronts form…
On the surface at the leading of an advancing thunderstorm
95
Roll and wall clouds occur…
In severe and fast moving thunderstorms
- Indicate presence of low level wind shear and extreme turbulence
96
What should you do if you see hail?
Circumnavigate thunderstorm by 10-20 miles downwind
97
How can you avoid thunderstorms while in the air?
Airborne radar (used to circumnavigate and avoid storms)
98
Thunderstorm penetration process
1. Penetrate perpendicular
2. Penetrate below the freezing level or above -15*C
3. Minimum altitude, 4000-6000’ AGL above highest terratin
99
What are microbursts and how long do they last?
They are intense, highly localized downward atmospheric flow w/ velocities of 2000 to over 6000 FPM, and last 2.5-5 minutes
100
What happens when taking off during a microburst?
1. Headwind causes IAS to jump upward rapidly
2. Nose pitches up
3. A/C begins to descend, but soon enters the other side of outflow
4. Headwind shifts to tailwind
5. IAS drops rapidly, probably causing a stall
101
How are microbursts detected?
Visually or from the ground (ground based)
102
What is a METAR and how frequently are the generated?
It is an hourly reported weather observation, and generated every hour (55-59 minutes)
103
What is a speci?
A special, unscheduled weather observation when critical data have changed from the previous observation
104
Decipher this: 09022G25
Winds 090 at 22 knots GUSTING 25 knots
105
RVR is encoded by
“R” followed by 2 digit runway and runway visibility in feet.
Ex: R13R6000 (Runway 13R, with RVR 6000’)
* Must specify the runway
105
What does a TAF include and when should you check it?
Includes worst weather conditions and surface window. Check it within +- 1 hour of ETA (0800 arrival = check b/w 0700-0900)
105
RVR is encoded by
“R” followed by 2 digit runway and runway visibility in feet.
Ex: R13R6000 (Runway 13R, with RVR 6000’)
* Must specify the runway
106
What is the TAF code for turbulence?
5
107
What is the TAF code for icing?
6
108
9999 in the TAF means…
7SM visibility or greater
