Weather Flashcards
(378 cards)
1
Q
Weather should be studied and learned
A
systematically and thoughtfully to accrue lifelong knowledge
AND
as if my life will depend on it
2
Q
Altitude is defined as the _____ and is displayed in the cockpit by an instrument called an ____
A
height above a given reference
altimeter
3
Q
Barometric altimeter
A
calibrated to display altitude in feet, as opposed to pressure in inches of mercury
4
Q
What kind of altitude is displayed on an altimeter?
A
True altitude (MSL)
5
Q
When flying from one location to another at a constant indicated altitude, you’re flying along a surface of constant?
A
Pressure
6
Q
When flying from one locale to another, a change in pressure of 1.0 inHg changes the altimeter reading
A
1000 feet
7
Q
How can you maintain a more constant AGL altitude when flying?
A
Updating the reference of the altimeter setting
8
Q
If you fly from an area of high pressure to an area of low pressure without changing your altimeter, what happens to your altitude?
A
You would have to descend to maintain a constant indicated altitude (i.e. be lower than you think you are).
“High to Low, Look Out Below”
9
Q
If you fly from an area of low pressure to an area of high pressure without changing your altimeter, what happens to your altitude?
A
You would end up higher than your altimeter is reading.
“Low to High, Plenty of Sky” or “Low to High, Clear the Sky”
10
Q
Does temperature deviations impact the altimeter?
A
Yes. Since altimeters are calibrated for a standard lapse rate, an incorrect indication results if the temperature deviates from the standard. For every 11 °C the temperature varies from the standard, there is a 4% altimeter error
11
Q
If the air is cooler than the standard atmosphere, the aircraft is ____ than the altimeter indicates.
A
Lower
12
Q
If the air is warmer than the standard atmosphere, the aircraft is ____ than the altimeter indicates.
A
higher
13
Q
Define indicated altitude
A
altitude as read on the altimeter
14
Q
Define absolute altitude
A
altitude is the aircraft altitude above the ground (AGL)
15
Q
Define true altitude
A
altitude referenced to mean sea level (MSL)
16
Q
Define pressure altitude
A
altitude above a standard datum plane (29.92 inches of mercury)
17
Q
Define density altitude
A
pressure altitude corrected for nonstandard temperature deviations. DA is not a height reference, but rather is an indication of aircraft performance
18
Q
What is the percentages of the atmosphere?
A
78% nitrogen, 21% oxygen, and a 1% mixture of 10 other gases
19
Q
Although the atmosphere appears relatively clear, it contains
A
nongaseous substances such as dust, salt particles, pollen, and others. These appear as haze and cause reduced visibility
20
Q
Height of the troposphere
A
Surface to…
55,000 feet at equator
28,000 feet at the poles
36,000 feet over United States
21
Q
What layer does nearly all weather take place in?
A
Troposphere (b/c of large amounts of moisture and condensation)
22
Q
What is the temperature like in the troposphere?
What about winds?
A
Temperature normally decreases with altitude (lapse rate)
Winds generally are light near the Earth’s surface and increase with altitude
23
Q
What is the tropopause?
A
a transition zone between the troposphere and stratosphere
24
Q
What is the height of the tropopause over the United States?
A
About 36,000 MSL
25
What is the temperature like in the Tropopause?
What does that produce?
The temperature in the tropopause is constant with altitude and is normally the coldest area in the lower atmosphere. As a result, contrails form and persist there.
26
What are the winds like in the Tropopause?
The strongest winds, those of the jet stream, occur just below the tropopause, resulting in moderate to severe turbulence. A haze layer with a definite top is also frequently found here.
27
What is the stratosphere and what altitude is it located at?
Above the tropopause is the stratosphere which is characterized by increasing temperature (inversion) as altitude increases, to approximately 66,000 feet.
28
What is flying generally like in the Stratosphere?
Since the air in the stratosphere is thin and offers little resistance, flying at this level is generally smooth with excellent visibility.
29
What is the standard temperature lapse rate?
The standard lapse rate is 2 °C per 1000 feet, although close to the surface, the rate may indicate an increase, decrease, or constant temperature when measured at increasing altitudes
30
What is an isothermal lapse rate?
The isothermal lapse rate indicates the temperature is constant with increasing altitude.
31
What is an inverted lapse rate (temperature inversion)? What are the conditions like within them?
An inverted lapse rate, also called a temperature inversion, generally occurs in the stratosphere when the temperature increases with increasing altitude. Conditions are usually stable within them.
32
What is atmospheric (barometric) pressure?
Atmospheric (barometric) pressure is the pressure exerted on the surface by the atmosphere due to the weight of a column of air directly above that surface
33
What is the average weigh of air on a square inch of Earth's surface at sea level?
14.7 pounds
34
How does pressure vary with altitude?
Unlike temperature, pressure always decreases with altitude. In the lower layers of the atmosphere, pressure decreases more rapidly than at higher altitudes because air density decreases as altitude increases.
35
What two units are used to measure atmospheric pressure?
inches of mercury (inHg) and millibars (mb)
36
What is the difference between inHg and mb?
Inches of mercury is the measure of the height of a column of mercury that can be supported by atmospheric pressure. The millibar is a direct measure of pressure, defined by force per unit area.
37
What is the range for normal sea level pressures?
28 inHg (about 960 mb) to 31 inHg (about 1060 mb)
38
What is a standard day at sea level? (4 things)
Pressure in 29.92 inHg
Temperature is 15 ºC
Lapse rate is 1 inHg/1000'
Lapse rate is 2 ºC/1000'
39
What is station pressure?
Station pressure is the atmospheric pressure measured directly at an airfield or other weather station
40
What is sea level pressure?
Sea level pressure is the pressure that would be measured from the existing weather if the station were at mean sea level (MSL)
It can be measured directly at sea level or calculated if the station is not at sea level using the standard pressure lapse rate
41
What is an isobar?
Lines of equal (sea level) pressures on a surface analysis chart
42
How are high pressure areas depicted on a surface analysis chart?
What about low pressure
Blue "H"
Red "L"
43
What do ridges v. troughs indicate on a surface analysis chart?
Ridges = high pressure and good weather
Troughs = low pressure and bad weather
44
With a pressure change of 1.0 inHg, how many feet will the altimeter reading change?
1000
45
If the air is colder than the standard atmosphere, the aircraft will be __________ than the altimeter indicates.
lower
46
In which atmospheric layer does weather normally occur?
Troposphere
47
The stratosphere is characterized by smooth flying conditions and excellent
visibility
48
What is the standard sea level temperature in degrees Celsius (°C)?
15
49
What is the standard temperature lapse rate of the atmosphere in °Celsius per 1000 feet?
2.0
50
The average weight of air on a square inch of the Earth’s surface at sea level under standard conditions is __________ pounds.
a. 14.7
51
Standard sea level pressure is 1013.2 mb or __________ inHg
29.92
52
The height of an aircraft above the ground is known as __________ altitude
a. absolute
53
For every 11 °C the temperature varies from the standard, there will be a __________% altimeter error.
4
54
Wind direction is always expressed in terms of
direction FROM which the wind is blowing
55
What are station models used for?
Station models depict wind direction and speed by use of a stick with barbs and pennants
56
What does the alignment of the stick mean on a station model?
The alignment of the stick indicates the direction the wind is blowing from in relation to TRUE NORTH
57
Are the following sources reported in relation to true north or magnetic?
Charts
Reports
Station Models
ATIS
Tower
RSU
True
True
True
Magnetic
Magnetic
Magnetic
58
What do the barbs and pennants indicate on a station model?
Wind speed
Pennant = 50 knots
Single barb = 10 knots
Half barb = 5 knots
59
How current is the mb and pressure change reported on a station model?
+/- 3 hours
60
What other information, besides winds, does a station model provide?
Present weather and sky cover, including temperature, present weather, dew point, and sky cloud coverage
Current pressure in mb and pressure change (± in last 3 hours)
Surface Charts and Winds
61
How do winds flow around high pressure areas?
Clockwise around high pressure
62
How do winds flow around low pressure areas?
Counterclockwise around low pressure
63
What does the spacing of isobars depict?
The spacing of isobars shows the rate of pressure change over a horizontal distance. Pressure changes more rapidly when isobars are more closely spaced. The rate of change in a direction perpendicular to the isobars is called the pressure gradient, and the isobar spacing represents the size of the pressure gradient force (PGF)
64
What is the initiating force for all winds?
The pressure gradient force (PGF)
65
Atmospheric circulation moves air by means of ascending and descending currents. What happens when air descends?
the downward force creates a high–pressure system on the surface. The air then spreads out and diverges producing horizontal flow, or wind.
66
Atmospheric circulation moves air by means of ascending and descending currents. What happens air moves upward?
Low-pressure system at the surface. Air tries to converge toward the center of this low–pressure area and produces wind.
67
How does Coriolis force affect wind direction?
This force diverts air to the right with respect to its initial direction of motion, regardless of whether the air is near a high or a low pressure system.
68
Where is Coriolis force strongest?
Above 2000 feet AGL (gradient winds)
Below 2000 feet AGL, friction reduces the speed of the wind
69
What direction do surface winds blow?
Across the isobars from high pressure to low pressure at a 45º angle
70
Where is wind speed the greatest? What layer of the atmosphere?
Wind speeds generally increase with height through the troposphere, reaching a maximum near the tropopause, and culminating in the jet stream
71
What is the average heigh of the jet stream and what is the average wind speed?
30,000 feet
100-150 knots
72
What flying direction in the jet stream requires more fuel consumption?
Westbound
73
What are local winds?
systems ranging from tens of miles across to long, geographically thin areas. These systems are created by mountains, valleys, and bodies of water
74
How are sea breezes produced? How do these breezes change between daytime and night?
Land is usually warmer than bodies of water during the day, and colder at night. In coastal areas, he pressure over land is lower and that over water is higher, causing the cooler air over water to move toward the lower pressure over land. This results in a sea breeze coming from the sea. At night, the pattern reverses and air moves from land to the sea. This should be considered for takeoff and landings near the coast
75
What is the difference between valley winds and mountain winds? How do they form?
During the day, mountain slopes are warmed by the sun and heat the adjacent air through conduction. Cool air settles downward toward the valley floor forcing warm air up the mountain. Since the air is flowing out of the valley, its called valley wind. At night, the air in contact with the slope is cooled by terrestrial radiation becoming denser. The denser air flows downhill and is called a mountain wind.
76
Low pressure results from __________ air.
ascending
77
What is the initiating force for all winds?
Pressure Gradient Force
78
The jet stream is the narrow band of strong winds found below the
tropopause
79
A half barb on a station model on a Winds-Aloft chart is equal to __________ knots
5
80
On a Surface Analysis Chart, the pressure systems mentioned are outlined by isobars drawn at __________- millibar intervals.
4
81
A strong pressure gradient force means a __________ wind speed.
faster
82
Jet Stream wind speeds average about __________ knots but can reach speeds in excess of __________ knots.
100 – 150; 250
83
Wind that is formed from denser air that flows downhill is called a
mountain wind
84
As water changes from one state to another, it releases (or absorbs) ___ to (or from) the atmosphere.
heat
85
Air can hold only a certain amount of water depending on the air temperature. The higher the temperature, the ____ water vapor the air can hold
higher temp = more water vapor
86
What is saturation?
Air reaches saturation when it contains the maximum amount of water vapor it can hold for a particular temperature
87
What is the dew point temperature?
the temperature at which saturation occurs and is a direct indication of the amount of moisture in the air
88
The higher the dew point, the ____ the chance for clouds, fog, or precipitation.
greater
89
What is dew point depression (i.e. dew point spread)?
The difference between the air temperature and the dew point temperature.
The dew point can never be higher than the air temperature, only equal to or less than.
90
What is relative humidity?
the percent of saturation of the air, or the percentage of water vapor in the air compared to the maximum amount the air could hold at that temperature
91
What are the three characteristics of precipitation?
Showers
Continuous
Intermittent
92
What are the three types of precipitation?
Drizzle
Rain
Frozen
93
What are clouds and why do they form?
Clouds are condensed water vapor, either water droplets or ice crystals. They are formed when the air becomes saturated either by cooling to the dew point or through the addition of moisture
94
Why are knowing clouds and their types important?
Clouds give visible evidence of the motion, water content, and degree of stability of the atmosphere. Knowing cloud types can help you visualize weather conditions and recognize potential weather hazards.
95
What are low clouds? Hazard to flight? Turbulence? Precipitation/icing?
-Low clouds have bases that range from SFC to 6500 AGL
-Serious Hazard to flight ops
-Turbulence is none to moderate
-Precipitation is light rain/drizzle
-can produce icing which accumulates faster due to the clouds being denser
96
What are Middle clouds (and their prefix)? Hazard to flight? Turbulence? Precipitation/icing?
-6500 to 20,000 AGL
-"alto"
-Visibility from 1/2 mile to a few feet
-Turbulence and rain/snow/mix
-Icing is common
97
What are high clouds (and their prefix)? Hazard to flight? Turbulence? Precipitation/icing?
-20,000 to 40,000 AGL
-"cirro" or cirrus
-No precipitation and NOT an icing hazard
-little effect on flight ops
-moderate turbulence and limited visibility (severe turbulence in anvil cirrus...thunderstorms)
98
What are cumulonimbus (cb) clouds?
exceedingly dangerous thunderstorm clouds
(extreme turbulence, hail, ICING, lightning, and other hazards)
99
What is considered a severe thunderstorm?
If the CB cloud extends past the Tropopause
100
What are nimbostratus clouds?
can produce continuous rain, snow, or ice pellets. They also produce poor visibility and low ceilings with very slow clearing
101
How is the stability of air mass determined?
the temperature of the surrounding air mass
102
Lifted air that is colder than the surrounding air indicates what type of condition? What about lifted air that is warmer? Same temperature?
Colder -> Stable condition (more dense)
Warmer -> Unstable condition (less dense)
Same temperature -> Neutrally stable
103
What are the four methods by which air masses are lifted?
Convergence: two masses converge and force air upwards
Frontal Lifting: cold fronts moving through an area lifts the air ahead of it
Orographic lifting: mountainside pushes air up
Thermal lifting: intense solar heating
104
Which clouds usually indicate stable conditions? Unstable?
Stratiform -> Stable
Cumuliform -> Unstable
105
What flight conditions typically indicate stable conditions?
Temperature inversions, low clouds or fog, rising temps while climbing, rime icing, poor visibility, smooth turbulence, and stratus clouds
106
What flight conditions typically indicate unstable conditions?
Cumulus clouds, rough turbulence, good visibility, gusty winds, showery precipitation, and clear icing
107
What types of clouds contain numerous hazards such as severe to extreme turbulence, hail, icing, and lightning?
Cumulonimbus
108
Three forms of precipitation are __________, __________, and __________.
drizzle; rain; frozen
109
The four methods of atmospheric lifting are convergence, frontal, thermal, and
orographic
110
__________ defines air with the same temperature as the surrounding air after being lifted.
Neutrally stable
111
Air is __________ when it contains the maximum moisture possible for a given temperature.
saturated
112
Thermal lifting is also called __________ and is caused when cool air is over a warm surface and is heightened by intense solar heating.
convective lifting
113
Names of middle clouds contain the prefix
alto-.
114
If the CB cloud extends past the __________, it is considered a severe thunderstorm.
Tropopause
115
Lifted air that is warmer than surrounding air continues to rise and indicates a(n) __________ condition.
unstable
116
What is an air mass?
A large body of air with uniform temperature and moisture conditions in a horizontal plane (no abrupt temperature or dew point changes within the air mass at a given altitude)
117
In the temperate zone (above the continental United States), what air masses may prevail?
both cold and warm air may prevail almost anywhere in the temperate zone at any season
118
How are air masses named?
according to their moisture content, location, and temperature
(location being the most important)
119
What kind of air masses have a greater potential for producing clouds and precipitation?
Moist
120
Most importantly, the _____ of an air mass indicates its stability. _____ air masses bring stable conditions, while _____ air masses are inherently unstable.
Temperature
Warm = stable
Cold = unstable
121
What is a front?
an area of discontinuity that forms between two adjacent contrasting air masses. A front can be thought of as a boundary between the two air masses.
122
What is a surface front? What about a frontal zone? Why are they important?
Surface front: The point where a front comes in contact with the ground
Frontal zone: the area that encompasses the weather on either side of the front
Most active weather is focused along and on either side of the surface front and the frontal zone. Most aviation weather hazards are found in this area.
123
If the temperature is warmer after a frontal passage, what is the front named?
A warm front
124
Other characteristics of fronts:
-Fronts are always located in a trough of ______
-Cold fronts generally move ____ than warm fronts
-Frontal passage is usually accompanied by a ___º shift in wind direction
Low pressure
cold fronts = faster
90º shift in wind direction
125
What is a good indicator of frontal intensity?
Amount and rate of temperature change
Abrupt = strong front
Gradual = weak front
126
What happens to pressure while flying towards and away from a front? Why is this important?
As a front approaches or a pilot flies toward a front, pressure decreases, then rises immediately after frontal passage. Because of this pressure change, it is extremely important to obtain a valid altimeter setting when flying in the vicinity of a front.
127
What dangers do fronts pose in respect to winds?
Frontal passage is accompanied by a wind shift, sometimes severe. Frontal wind shifts can create hazardous wind shears in the vicinity of an airfield
128
What clouds usually produce steady precipitation and little to no turbulence? What clouds usually bring showery precipitation and turbulence?
Stratiform = steady and no turbulence
Cumuliform = showery and turbulence
129
What is the slope of the front? How do steep slopes compare to shallow slopes?
slope of the front is the ratio of vertical rise to horizontal distance
shallow front = extensive cloudiness with steady precipitation
steep slopes = rapid moving, narrow band showery, severe weather
130
How does the speed of a front effect its characteristics?
Faster moving fronts are generally accompanied by a narrow band of more severe weather, while slower moving fronts have less severe weather, but the frontal zone is more extensive.
131
The greater the contrast in the _____ and ______ between the two air masses, the greater the possibility of weather associated with a front, particularly severe weather.
temperature and moisture
132
What type of front creates the steepest frontal slope?
Cold front
133
As a cold front wedges under a less denser warm air mass, what happens?
the cold air pushes the warm air upward, this lifting creates unstable conditions, producing sometimes very violent conditions, including strong thunderstorms and severe turbulence.
134
How do winds shift with cold fronts? As the cold front approaches what happens to wind speed and barometric pressure?
wind shifts approximately 90° from SW to NW
Generally, as the front approaches, wind speed increases and barometric pressure decreases (lower cloud bases + rain/snow)
135
What is a squall line and how are they indicated on a surface chart?
A squall line is a line of violent thunderstorms. They are indicated on surface charts by a dashed, double–dotted purple line.
136
How many miles ahead of a cold front do squall lines develop? How are squall lines positioned relative to the cold front?
Squall lines usually develop 50 to 300 miles ahead of the cold front, and roughly parallel to it, although sometimes they can be located nowhere near a cold front.
137
Why are squall lines important to aviation?
Squall lines are a severe hazard to aviation. It is often impossible to fly though a squall line, even with radar, due to the storms being extremely close to one another.
138
What properties are used to locate and classify fronts?
Temperature, dew point, pressure, wind
139
What parameters of an air mass are generally uniform when measured across a horizontal plane?
Temperature and moisture
140
How do the winds shift during a cold front passage?
SW to NW
141
Squall lines generally develop where?
50 – 300 miles ahead of the cold front
142
What parameters of an air mass are generally uniform when measured across a horizontal plane?
Temperature and moisture
143
A line of violent thunderstorms that forms ahead of a cold front is known as a
squall line
144
Every front is located in a
low pressure trough.
145
Which frontal system has a steeper slope?
A cold front.
146
What do warm fronts create?
a broad area of cloudiness, steady precipitation, and reduced visibility
147
How far out do warm fronts effect?
500-700 miles
148
A warm front typically moves at a ____ speed than a cold front and produces a more ____ frontal slope, sloping forward and ahead of the surface front. Because of these factors, warm fronts are not as well ____ as cold fronts
slower
gradual slope
NOT as well defined
149
How do winds shift from a warm front?
SE to SW
150
What is a stationary front?
the frontal border between air masses shows little or no movement, with neither air mass replacing the other
151
How does a stationary front impact winds?
Surface winds along a stationary front tend to be parallel on both sides of the front rather than against or away from it. Thus, a stationary front has a 180° wind shift
152
What are weather conditions like with a stationary front?
Weather conditions associated with a stationary front are similar to those found with a warm front but are usually less intense
153
What is an occluded front?
When a faster moving cold front overtakes a slower moving warm front.
There are two types of occluded fronts: cold and warm. The type of occluded front depends upon which front remains in ground contact. If the cold front remains in contact with the ground, it is a cold front occlusion, and vice–versa.
154
How are occlusions shown on surface charts?
both cold and warm front symbols pointed in the same direction, and colored purple
155
How do occlusions impact the winds? What is the weather like for the front and where will the most severe weather be?
The wind shift across either type of occlusion will be 180°, and because the occlusion is a result of the meeting of cold and warm fronts, associated weather will be a combination of both types of frontal weather.
Most severe weather: 100 miles south to 300 miles north
156
What is a dry line?
also called a Dew Point line, is a boundary between moist and dry air masses. Unlike a cold or warm front, one airmass is not rapidly overtaking the other. The temperature is relatively the same, but there is a large difference in moisture content
157
Why should dry lines be avoided?
The rapid rise of the moist air can result in rapidly formed severe thunderstorms including hail, tornadoes, high winds, etc. that should be avoided
158
How do the winds shift during a warm front passage?
SE to SW
159
When encountering a stationary front, you can expect a __________° wind shift since surface winds tend to blow parallel on both sides of the front.
180
160
When flying through an occluded front, you can expect weather associated with __________ fronts.
both cold and warm
161
The most severe weather with respect to an occluded front is generally located __________ NM south to __________ NM north of the frontal intersection.
100; 300
162
A line of rapidly forming thunderstorms is normally associated with
a dry line.
163
What type of weather is usually associated with a stationary front?
Weather similar to a warm front, but usually less intense
164
Occluded fronts form when a faster moving cold front overtakes a slower moving __________ front.
warm
165
A dry line, also called a dew point line, is a boundary between __________ air masses and can rapidly trigger severe thunderstorms.
moist and dry
166
What is turbulence?
irregular or disturbed atmospheric flow producing wind gusts and/or eddies
167
How is turbulence reported and forecasted? What are the categories?
air turbulence is graded on a relative scale, according to its perceived or potential effect on a ‘typical’ aircraft
Light, Moderate, Severe, Extreme
168
What is light turbulence?
Light turbulence is a series of momentary, slightly erratic changes in your altitude or attitude. It will affect all three axes of pitch, roll, and yaw. You may feel a slight strain against your seat belt and/or shoulder straps. Small unsecured objects might get dislodged in your cockpit.
169
What is moderate turbulence?
Moderate turbulence is similar to light turbulence but somewhat more intense. There is, however, no loss of control of the airplane.
-Larger changes in altitude and/or attitude
-Variations in indicated airspeed
-Definite strain against seat belts and shoulder straps
-Unsecured objects dislodged
170
What is severe turbulence?
Severe turbulence causes large and abrupt changes in altitude and/or attitude and, usually, large variations in indicated airspeed. The aircraft may momentarily be out of control.
-uncommanded control inputs
-substantial strain
-objects launched in the cockpit
171
What is extreme turbulance?
the aircraft is violently tossed about and is practically impossible to control...structural damage is a distinct possibility
172
What are the three categories of frequency (duration) for turbulence? How are they defined?
Occasional - Less than 1/3 the time
Intermittent - 1/3 to 2/3 of the time
Continuous - More than 2/3 of the time
173
How is turbulence displayed on a weather chart?
Green arrow: light
Yellow arrow: moderate
Double red arrow: severe
Quadruple red arrow: extreme
174
What are the 4 causes of turbulence?
Thermal - unequal heating of Earth's surface
Mechanical - friction between the air and ground/buildings
Frontal - lifting of the warm air between two opposing air masses
Wind Shear - change in wind direction and/or wind speed
175
What is clear air turbulence (CAT)? What kind of turbulence is it?
It is a kind of shear turbulence
CAT is turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet.
176
What atmospheric region is most susceptible to CAT?
High troposhere (23,000 - 39,000) where it meets the tropopause
(CAT is most frequently encountered in the regions of the jet stream)
177
Where does CAT frequently occur at low altitudes?
Near mountain ranges
Smooth lenticular clouds and ragged rotor clouds many times indicate a high probability of CAT
178
What is the commonly expected turbulence generated on warm days?
Thermal Turbulence b/c the sun heats the earth's surface unevenly
179
What time of the day is thermal turbulence the least pronounced?
Early morning or late in the evening, when daytime heating does not have the same effect
180
What factors increase the intensity of eddy motion caused by mechanical turbulence?
The intensity of this eddy motion depends on the strength of the surface wind, the nature of the surface and the stability of the air.
(Stronger wind, rougher terrain, and more unstable air = greater turbulence)
181
What are mountain waves and what kind of turbulence are they?
Mountain Waves are turbulent eddies that are found up to 150 miles downwind from mountain ridges as a result of winds in excess of 50 knots (a type of mechanical turbulence)
182
As they are caused by mountain ridges, mountain waves are ____ and therefore more predictable. Mountain waves produce some of the most ____ turbulence.
stationary; severe
183
What are characteristics of mountain wave turbulence? What clouds indicate their possibility?
Winds 25+ knots blowing perpendicular to top of mountain ridge
Main updraft and downdraft can displace aircraft up to 5,000 ft/min
denoted by:
Cap Clouds (stationary clouds on the top of a mountain)
Cirrocumulus Standing Lenticular (CCSL)
Altocumulus Standing Lenticular (ACSL)
Rotor clouds (often associated with the most intense turbulence)
184
What ways can you mitigate mountain wave turbulence? (5)
-Circumnavigate
-Fly 50% higher than the mountain peak
-Avoid rotor, cap, and lenticular clouds
-Approach mountain range at a 45º angle
-Avoid strong downdrafts on leeward (facing away from the wind; downwind) side of mountain
185
What kind of front is turbulence more commonly associated with?
Cold fronts, particularly fast moving
186
When is frontal turbulence most marked?
When the warm air is moist and unstable (also it will be extremely severe if thunderstorms develop)
187
What atmospheric conditions where wind shear exist?
Temperature inversions, along troughs and lows, and around the jet stream
188
Where is the greatest shear (and thus the greatest turbulence found)?
The greatest shear, and thus the greatest turbulence, is found at the tops of the inversion layer. Strong stability prevents mixing of the stable low layer with the warmer layer above. (the closer this occurs to the ground, the worse it is)
189
Where is wind shear the strongest in the jet stream?
on the cold/low pressure side (north in the northern hemisphere)
190
In order to combat turbulence, what airspeed/attitude/power/altitude should be flown?
Attitude is the key!!
Airspeed: penetration airspeed of 180 KIAS is recommended. Do NOT exceed Vg of 195 KIAS. Do NOT chase the airspeed
Attitude: this is the key for proper flight through turbulence. Do NOT trim after the proper attitude has been established and do NOT make abrupt changes
Power: Establish the throttle setting needed for the attitude
Altitude: allow altitude to vary in order to maintain attitude. Do NOT chase the altimeter
191
The four levels of intensity of turbulence are __________, __________, __________, and __________.
Light, Moderate, Severe, and Extreme
192
The four classifications of turbulence are __________, __________, _________, and _________.
thermal, mechanical, frontal, and wind shear
193
What type of frontal activity is likely to produce the most turbulence?
fast moving cold front
194
All of the following are methods to combat turbulence EXCEPT
a. establish and maintain a power setting.
b. maintain pitch and bank by reference to the EADI.
c. set an airspeed of 180 KIAS, but don’t chase it.
d. rigorously hold your altitude.
(d) rigorously hold your altitude
195
What are the four levels of turbulence intensity?
Light, Moderate, Severe, and Extreme
196
Possible actions to mitigate mountain wave turbulence include all of the following EXCEPT
a. circumnavigate if possible.
b. avoid rotor, cap, and lenticular clouds.
c. maximize airspeed to minimize exposure time.
d. avoid strong downdrafts on the leeward side.
(c) maximize airspeed to minimize exposure time
197
Turbulence occurring less than 1⁄3 of the time is described as
occasional
198
Wind shear can be defined as
the change in wind direction and/or wind speed over a specific horizontal or vertical distance.
199
Mountain wave turbulence updrafts and downdrafts can displace an aircraft up to __________ feet per minute.
5,000
200
What two units are used to measure atmospheric pressure?
millibar and inHg
201
What is standard Day temperature lapse rate?
2º C per 1000 feet
202
Winds in the jet stream average between __________ and __________ knots but can be as high as __________.
100-150, 250
203
Describe intermittent precipitation
Stops and starts at least once during the hour, may be showery or steady, associated with cumuliform or stratiform
clouds.
204
How are occluded fronts indicated on a weather chart?
Cold and warm fronts pointed in the same direction, colored purple
205
Where do squall lines usually develop?
50 to 300 miles ahead of a cold front, roughly parallel.
206
A sudden change in wind speed or direction over short distance, vertically or horizontally describes what?
Wind shear
207
What are the four turbulence classifications?
Light, Moderate, Severe, Extreme
208
What are the two main groups of aircraft icing?
Structural icing and engine icing
209
Why is icing bad?
Icing is a major hazard to aviation. It reduces aircraft efficiency by reducing aerodynamic capability, as well as impairing engine performance
210
What is structural icing? What is the main concern of structural icing?
the formation of ice on the exterior of an aircraft (Figure 109-3) during flight through clouds or liquid precipitation when the air and skin temperature is equal or less to 0 °C
The main concern of structural icing is the loss of aerodynamic efficiency due to an increase in drag and a decrease in lift.
211
What is engine icing ? What is its main concern?
occurs when ice forms on the induction or compressor sections of an engine, reducing performance. Compromised engine operation and FOD can result from this type of icing.
212
What is generally required for icing?
A source of moisture
Air temperature and aircraft surface of 0 ºC or colder
213
What is the most common source of moisture?
Clouds
214
The smaller and purer the droplets, the ____ their freezing points are
lower
215
Can icing be possible in temperatures above freezing?
Yes. If an aircraft has been in below freezing temperatures and then is in above freezing temperatures, the aircraft’s surface temperature can remain below freezing for some time. Therefore, icing still may be possible in temperatures that are above freezing
216
What are the three categories of icing?
Clear, Rime, and Mixed
217
What is clear icing?
Clear ice is a glossy, clear, or translucent ice usually formed in relatively warm temperatures, between 0 °C and -1 °C. In addition to the warm temperatures, the other key ingredient is lots of water
218
Where is clear icing generally found?
In cumulus clouds and unstable conditions
219
What is rime icing?
Rime ice is an opaque, or milky white, deposit of ice that forms when the airplane (Figure 109-10) is flying through filmy/stratiform clouds, with temperatures generally between 0 °C and -30 °C. It is dependent on a low rate of catch of small, supercooled water droplets. It accumulates on the leading edges of wings and on antennas, pitot tubes, etc. For rime to form, the aircraft skin must be at a temperature below 0 °C. The drop will then freeze completely and quickly without spreading from the point of impact.
220
Which type of icing assumes the shape of the airfoil?
Clear (Rime is irregularly shaped)
221
Where is rime icing generally found?
Stratiform clouds and stable conditions
222
What is mixed icing?
has the properties of both clear and rime icing. It has large and small supercooled droplets that coexist. Mixed icing’s appearance is whitish, irregular, and rough. The formation process for mixed icing includes that of clear and rime icing. Mixed ice can accumulate rapidly and is difficult to remove.
223
When does mixed icing typically form?
liquid and frozen particles found in the colder portion of the cumuliform cloud and wet snowflakes. It is generally found at temperatures between -10 °C and -15 °C and can appear as lumpy (like rime) but hard and dense (like clear)
224
What icing typically occurs at these temperatures?
10 ºC or colder
air and skin temperature is less than or equal to 0 ºC
Engine
Structural
225
What is frost?
Not an "official" type of icing. Frost, many times, occurs on clear, calm nights when the lack of clouds promotes radiational cooling. Furthermore, the presence of little or no wind allows moisture to deposit as ice crystals (deposition). The upper surfaces of the aircraft cool by radiation to a temperature below that of the surrounding air
226
Does frost have a major effect on flying in most circumstances?
No. However, it may obscure vision by coating the windscreen. It can also alter the aircraft's aerodynamics to increase takeoff stall speed so it must be removed
227
What are the four levels of icing severity?
Trace, Light, Moderate, and Severe Icing
228
What is trace icing?
Ice becomes perceptible. Rate of accumulation is slightly greater than the rate of sublimation. Occasional use of anti-ice equipment.
229
What is light icing? What is its rate of accumulation?
The rate of accumulation (1/4-inch in 15-60 minutes) is such that the occasional use of ice protection systems is required to remove or prevent accumulation.
230
What is moderate icing? What is its rate of accumulation?
The rate of accumulation (1/4-inch in 5 – 15 minutes) is such that frequent use of ice protection systems is necessary to remove or prevent ice. Unless actions are taken, substantial amounts of ice will build on the airfoil.
230
What is severe icing? What is its rate of accumulation?
The rate of accumulation (1/4-inch in less than 5 minutes) is so fast that ice protection systems fail to remove the accumulation of ice. Severe icing is usually a product of a clear or mixed icing encounter. Immediate diversion may be necessary.
230
When can light icing become a problem?
Rate of accumulation may create a problem if flight is prolonged greater than 1 hour. Light icing should not be a problem if anti-icing and/or de-ice is used
231
What impact does warm fronts have on icing? At what distance from the warm-front surface position?
Icing may occur both above and below the frontal surface. Moderate or severe clear icing usually occurs where freezing rain or freezing drizzle falls through the cold air beneath the front.
There is a definite possibility of moderate icing, usually mixed or clear, within 100 to 200 miles ahead of the warm-front surface position.
232
What characteristics of a warm front make icing particularly noticeable?
fast-moving, active, warm fronts.
233
How is cold front icing different than warm front icing?
It is usually spotty. Its horizontal extent is less, and the areas of moderate icing are localized. Light icing is often encountered in the extensive layers of supercooled stratocumulus clouds which frequently exist behind cold fronts.
234
What is icing like for occluded and stationary fronts?
Icing conditions associated with occluded and stationary fronts are similar to those of a warm or cold front (Figure 109-23), depending on which type the occlusion or stationary front most resembles. Moderate icing conditions are frequently associated with deep, cold, low-pressure areas in which the frontal systems are quite diffuse.
235
The most profound degradation of structural icing that manifests on aircraft performance usually occurs within
the first few minutes of ice accretion
236
What are the aerodynamic effects of icing?
Decrease climb rate
Decrease cruise speeds
Increase stall speed
Decrease service ceilings
Decrease missed approach performance Increase fuel consumption
Decrease maximum range
237
How does icing impact instrument readings and communications?
Icing of the pitot tube reduces ram air pressure on the airspeed indicator and renders the instrument unreliable. cing of the static ports (Figure 109-27) reduce reliability of all instruments on the pitot static system including the airspeed, VSI, and altimeter. Additionally, ice forming on the myriad of antennas distorts their shape, increases drag, and imposes vibrations that may result in failure or degradation of the communications system of the aircraft.
238
Why is icing of the AOA vane particularly dangerous?
Icing of the AOA vane could render the stall warning system ineffective. This could be particularly dangerous during takeoff and landing.
239
Where is the T-6 been approved for transit in icing conditions?
5000-foot band of light rime ice
240
What should pilots do in regards to icing conditions?
Icing conditions should be avoided. Pilots should steer clear of freezing temperatures and below with visible moisture
When actual icing conditions are encountered, pilots should climb or descend to exit the icing condition, or to encounter warmer air. Many times, it is more expedient to climb above the moisture, or climb into colder conditions to sublimate (that is the process of ice changing into water vapor in the air without first melting into water) than to melt the ice via warmer conditions.
241
What protection does the T-6 have against icing?
protection for critical systems and cockpit displays through the use of heated pitot masts and a heated angle-of-attack sensor. The fuel system is protected with external fairings to prevent accumulation of ice on fuel tank vent ports. External static ports are located on the aft fuselage to eliminate exposure to icing. No heating is provided for the static ports as the ports are protected from icing by airframe location.
242
Does de-icing occur in the T-6?
Generally, no. Using a heated hangar or cover is the first choice in preventing icing. Heating is the only method allowed for deicing the canopy and, if used, the maximum temperature of the transparency is 150 °F.
243
What greatly reduces the incidence of engine ice ingestion in the T-6?
the particle separator in the engine intake duct
244
What are some hazards of icing on/near the ground?
Stopping distance, wet control surfaces, ice on windscreens, gear/flaps freezing in the retracted position
245
What type of icing is found in cumuliform clouds and unstable conditions?
Clear
246
There is a definite possibility of moderate icing, usually mixed or clear, within __________ to __________ miles ahead of the warm-front surface position.
100; 200
247
Occasionally refer to the __________ for the most up to date icing severity definitions and how to report them appropriately.
a. Flight Information Handbook (FIH)
b. IFR Supplement
c. Airmen’s Information Manual (AIM)
d. Botha and c
both a and c
248
The most profound degradation of structural icing that manifests on aircraft performance usually occurs within __________ of ice accretion.
the first few minutes
249
What are the greatest hazards associated with engine icing?
Reduced airflow and engine FOD
250
What are the two types of icing?
Structural and engine
251
Air intake icing requires __________ moisture and __________ temperatures.
visible; +10 °C or colder
252
When icing conditions are encountered, pilots should __________ or __________ the icing condition.
a. climb above
b. descend below
c. plough through
d. Both a and b
Both a and b
253
After takeoff from a runway covered by snow or slush, operate the __________ several times to expel wet snow or slush and to prevent freezing.
a. brakes
b. canopy
c. gear and flap
d. Both a and c
both a and c
254
What type of icing is found in cumuliform clouds and unstable conditions?
Clear
255
How is visibility reported?
Statute miles, hundred of feet, or meters
256
What is flight visibility?
the average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.
257
What is prevailing visibility?
the greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous. It is also measured in statute miles
(the visibility that is considered representative of conditions at the station)
258
Does prevailing visibility need to be continuous?
No. It just needs to be at least half of the horizon
259
What is slant range visibility?
the visibility from the cockpit to the ground and features ahead; it’s the view down the approach path (indicates when an aircraft will "break out" on final
260
What is runway visual range?
an instrumentally derived value that represents the horizontal distance that a pilot can see down the runway. It’s the maximum distance at which the runway or the specified lights or markers delineating it, can be seen from a position above a specified point on its centerline at a height corresponding to the average eye level of pilots at touchdown
261
What measures runway visual range?
Transmissometer
262
What does it mean if visibility is reported as obscured?
something is blocking your view of the sky AND the clouds (dust, haze, pollution, heavy snow, etc)
263
When will vertical visibility be reported? What is it?
If the entire sky is entirely obscured. Vertical visibility is the visibility straight up from a given point
264
What are the cloud cover conditions? What does each one correlate to?
SKC (Clear): 0/8
FEW: >0/8 - 2/8
SCT: 3/8 - 4/8
BKN: 5/8 - 7/8
OVC: 8/8
VV (Obscured): 8/8 (Surface based)
265
What is a ceiling? What is the summation principle?
the height ascribed to the lowest layer of clouds or obscuring phenomena using the summation principle. The summation principle states that the sky cover at any level is equal to the summation of the sky cover of the lowest layer plus the additional sky cover present at all successively higher layers up to and including the layer being considered.
If there is 1⁄2 of the sky covered at 12,000 ft, and another 1⁄4 of the sky covered at 5,000 ft, the sky above the 5,000 ft layer is assumed to also have clouds at 12,000 ft. This would then result in 3⁄4 of the sky covered with cloud and a BKN ceiling at 12,000 ft
266
What is fog?
a surface level cloud. It occurs when the atmosphere is saturated, or nearly saturated, with moisture. This occurs when temperature and dew point are brought close together. It is a visibly large area of condensed moisture within 50 feet of the surface which reduces visibility to less than 5⁄8 mile.
267
What is the two most common types of fog in aviation?
Radiation Fog: Caused by radiational cooling of the earth’s surface, this type of fog can significantly affect aviation operations. Radiation fog develops only at night and over land. In most cases, radiation fog is nocturnal – becoming thickest at night, right around sunrise, and dissipating by late morning
Advection Fog: This is generated by fog in motion. It develops in one region and is transported by wind currents to a different location. This type of fog typically occurs along coastlines or between a cold wet surface and a warmer drier surface. Advection fogs can persist for days and has a greater impact on aviation operations than radiation fog.
268
What type of fog has a greater impact on aviation operations?
Advection Fog
269
What 3 conditions must be meet for fog to form?
-Condensation nuclei present
-The air must have a high water content (low temperature/dew point spread).
-Light surface winds (less than 10 knots) must be present
270
Why are volcanic ash clouds dangerous to aviation operations? What problems are there with detecting it?
Ash particles can wear away forward-facing surfaces, including windscreens, fuselage surfaces, and compressor fan blades. Ash contamination also can lead to failure of critical navigational and operational instruments. Moreover, the melting temperature of the glassy silicate material in an ash cloud is lower than combustion temperatures in modern jet engines. Consequently, ash particles sucked into an engine can melt quickly and accumulate as re-solidified deposits
Ash is difficult to see at night and generally does not show up on weather radar
271
What is the key to dealing with volcanic ash? What should you do if you get caught in volcanic ash?
Avoidance. Make a 180º turn to escape
272
Slant-range visibility is the visibility from the __________ and features ahead.
cockpit to the ground
273
A ceiling is the height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported at least __________ and not classified “thin” or “partial” as determined by the summation principle.
5/8
274
Fog occurs when ____ and ____ are brought close together
temperature and dew point
275
If an aircraft encounters an ash cloud in flight what is the best procedure for the pilot to use to escape the cloud?
Execute a 180° turn
276
__________ visibility is the greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous.
Prevailing
277
Total visibility over half the horizon circle or greater is
prevailing visibility
278
The lowest layer of clouds or obscuring phenomena when it is reported as broken, overcast, or obscuration and not classified “thin” or “partial” as determined by using the summation principle” best describes
a ceiling.
279
In order for fog to form, the three basic conditions of __________, __________, and __________ are required.
condensation nuclei; low temperature/dew point spread; light surface winds
280
The key to dealing with volcanic ash is?
avoidance
281
What three things are needed for convection to be a significant hazard to flight safety?
Moisture, Lift, Instability
282
What are the hazards associated with thunderstorm turbulence?
-up and down drafts exceeding 6000 ft/min
-changes in altitude
-structural damage and stress on airframe
283
What is a gust front?
a line of dangerously gusty winds created on the leading edge of an advancing thunderstorm
284
Why do gust fronts happen? How can they be seen on radar?
When a downdraft from a raining thunderstorm hits the ground, it spreads out in all directions. This spreading air can move very fast, and as it spreads, it can create a gust front
On radar, a gust front can be seen as a thin line of reflectivity moving away from the storm. This reflectivity signature may be caused by convection, or the result of insects, dust, dirt, or vegetation being kicked up with the winds.
285
What is a roll cloud?
a relatively rare, low-level horizontal, tube-shaped cloud completely detached from the cumulonimbus base. Roll clouds are located along the gust front and are most frequently observed on the leading edge of a line of thunderstorms, a cold front or line of squalls.
286
What is a wall cloud?
a local, often abrupt lowering from a cumulonimbus cloud base, normally a kilometer or more in diameter. A wall cloud marks the lower portion of a very strong updraft, usually associated with a supercell or severe multicell storm
287
What do both roll clouds and wall clouds indicate?
low level wind shear and extreme turbulence as they occur in severe and fast moving thunderstorms
288
Wall clouds that exhibit significant rotation and vertical motion often precede?
Tornados
289
How does hail form?
Hail begins as rain, lifted by updrafts in a thunderstorm. As the water droplet is carried upward, it freezes. The bigger the storm, the more the cycle continues until each ice pellet becomes too heavy for the power of the updraft.
290
Hailstones larger than __ to __ of an inch can cause significant damage to an aircraft in a few seconds
1/2 to 3/4 of an inch
291
Does hail just come out of the bottom of clouds?
No. It can be ejected from the top of some larger storms. Large thunderstorms are maelstroms of updrafts and downdrafts. When hail is caught in an updraft, it can be thrown out the top of the storm for dozens of miles
292
Why does lightning happen?
Lightning occurs as a result of a buildup of static charges within a Cumulonimbus cloud, often associated with the vertical movement and collision of ice particles (Hail), which result in a negative charge at the base of the cloud and a positive charge at the top of the cloud
293
An aircraft passing close to an area of charge can initiate a discharge and this may occur some distance from a Thunderstorm. Lightning strikes on aircraft commonly occur within ____ feet of the freezing level
5,000 feet
294
Does all lightning strike the ground?
Not all lightning strikes the ground. Cloud flashes sometimes have visible channels that extend out into the air around the storm (cloud-to-air or CA) or remain within the cloud and are called intra-cloud (IC) lightning flashes.
295
In most cases, does lightning compromise safety of pilots?
Although a lightning strike can be quite an unpleasant experience for the pilots, in most cases it does not cause much physical damage to the plane, nor does it compromise safety. Typically, lightning hits certain parts of an aircraft like a wingtip or the nose. The charge then travels through the airplane’s metal shell before leaving at another point like the tail.
296
What are some possible effects of lighting on an aircraft (4)?
-can strike aircraft flying in the clear
-structural damage is possible
-catastrophic fuel ignition possible
-pilot flash blindness
297
What is St. Elmo's Fire? Is it a hazard?
occurs when the atmosphere’s static buildup is enough to cause a discharge (plasma) between an object and the air around it. While not a hazard in itself, St Elmo’s Fire is an indication of thunderstorm activity and may be a precursor to a lightning strike.
298
What are tornadoes? How fast can the winds reach?
violent, rotating columns of air that descend from cumulonimbus clouds in funnel-like or tube-like shapes.
up to 300 miles per hour
299
Is tornado damage limited to airborne aircraft?
Damage isn’t limited to airborne aircraft. Aircraft involved in ground operations are extremely susceptible to the damage doled out by a tornado.
300
What 2 things are definitionally true about tornadoes?
1. Tornadoes touch the ground
2. Funnel clouds do not touch the surface
301
What is a waterspout?
occurs the rotating column touches a water surface
302
What is a Tornadic Vortex Signature (TVS) and why is it important?
a Doppler radar velocity pattern that indicates a region of intense concentrated rotation. The TVS appears on radar several kilometers above the ground before a tornado touches ground. It has smaller, tighter rotation than a mesocyclone. While the existence of a TVS does not guarantee a tornado, it does strongly increase the probability of a tornado occurring
303
A direct relationship exists between what things when tracking thunderstorms? (3)
Strength of radar echoes
Presence of aircraft icing
Intensity of turbulence
304
What indicates severity of thunderstorms?
Heigh of tops of CBs (Cumulonimbus clouds)
305
What is airborne based radars used for and what are some of its characteristics?
-Unlike ground-based radars, airborne based radars are used to circumnavigate and avoid the storms
-Not used to identify aspects of the storm or predict future hazards
-"Soft spots" may seem benign but may still produce hazards
-angle off of the nose is moveable
-brighter the area, the more severe the storm. Note the black areas behind the storm. This is telling the pilots that the storm is so severe that it is absorbing all of the radiated energy
-severe turbulence can be expected between storms
306
How far should severe thunderstorms be avoided by?
at least 20 miles
307
If you cannot avoid a thunderstorm, is it better to fly over or under the storm?
Attempting to fly over the storm can avoid most hazards, but keep in mind hail can exit at the top of a storm. Be at least 1000 feet higher than the top of the storm for every 10 knots of wind speed at the cloud top. At high altitudes, trying to outclimb a thunderstorm can be very hazardous.
attempting to fly under a thunderstorm is likely the most dangerous method to attempt.
308
What are some procedures if you must fly into a thunderstorm?
-Penetrate perpendicular to minimize time in storm.
-Penetrate the storm below the freezing level or above the -15 °C level.
-Minimum altitude should be 4000 to 6000 feet AGL above the highest terrain.
-Fly turbulent air penetration speed
-Turn OFF autopilot
-secure loose items
309
Roll and wall clouds indicate
low level wind shear and extreme turbulence.
310
Lightning strikes on aircraft commonly occur within __________ feet of the freezing level.
5,000
311
Be at least __________ feet higher than the top of the storm for every 10 knots of wind speed at the cloud top.
1000
312
If you find yourself with no other alternatives but to penetrate an area of thunderstorms, penetrate __________ to minimize time in the storm.
perpendicular
313
What combination of atmospheric conditions is necessary for the formation of a thunderstorm?
Moisture, unstable air, lifting action
314
What effects can turbulence have on an aircraft?
Altitude deviations, structural damage, airframe stress
315
What hazards are associated with lightning?
Structural damage, flash blindness, static buildup
316
Roll and wall clouds indicate
a severe and fast-moving thunderstorm.
317
A __________ forms on the surface at the leading edge of an advancing thunderstorm.
gust front
318
What is a microburst? (4 requirements)
-downdraft (sinking air)
-formed in a thunderstorm
-less than 2.5 miles in diameter
-usually lasts between 2 and 5 minutes
319
Although microbursts can pose a threat to life and property, is there a threat to aviation?
YES. All microbursts pose a significant threat to aviation
320
A microburst will present with an _____ and indicated airspeed, followed by a ____ with decreasing indicated airspeed.
increasing headwind -> tailwind
321
How fast can wind speeds reach in microbursts and how strong can the downward flows reach?
Wind speeds as high as 150 mph are possible in extreme microburst cases. Intense, highly localized downward atmospheric flow velocities can reach to over 6000 feet per minute.
322
Microbursts can be either wet (rain reaches the surface), dry (little or no rain reaches the surface), or a hybrid of the two. In all circumstances, however, the development mechanisms are generally
the same
-cooling beneath the thunderstorm base
-sublimation
-evaporation
-rain and/or hail
323
When do microbursts happen?
Microbursts can occur during any time of the year. However, as microbursts are associated with thunderstorms, we generally associate them with developing during the warmer months of the year.
324
What type of microburst is more difficult to see?
a dry microburst can be more difficult to see as there may not be a visible rain shaft immediately above the microburst. Visible dust and debris being kicked up on the ground is a good clue about the presence of a microburst. This wall of dust, known as a haboob, is being pushed out along the ground from a thunderstorm microburst that can be miles away.
325
How is damage from microbursts different than from tornadoes?
Generally, when large swaths of objects such as trees are all blown over in the same direction, straight-line winds many times from a microburst are the culprit. When objects are in general disarray or there is a twisting characteristic to the damage, it’s likely due to a tornado.
326
How should microbursts be dealt with on takeoffs and landings?
Takeoffs -> Should be avoided
Approach -> an immediate missed approach or go-around should be executed with max power (Figure 112-7). Whether on the missed approach/go-around or landing, power should be maintained until exiting the outflow portion of the microburst or safely down on the ground as a rapid decrease in headwind and therefore lift, will most likely be encountered
327
What are visual cues of a microburst? (4)
-Virga (precipitation that evaporates before reaching the ground)
-Localized blowing dust
-shaft of rain which diverges closer to the ground
-severe thunderstorms/cumulonimbus clouds
328
Microbursts are an intense, highly localized downward atmospheric flow with velocities of up to __________ feet per minute.
6000
329
Which of the following is not a valid method of identifying a microburst?
a. Visual cues (rain shafts, virga, etc.)
b. The presence of structural icing
c. Pilot Weather Reports (PIREPs)
d. A sudden and noticeable change in indicated airspeed
the presence of structural icing
330
If landing during microburst conditions, do not __________ power to idle until safely on the ground.
decrease
331
Wind speeds as high as __________ mph are possible in extreme microburst cases.
150
332
Microburst development is generally seen during the __________ months of the year.
warmer
333
A microburst is a __________, formed in a thunderstorm, less than __________ miles in diameter.
downdraft (sinking air); 2.5
334
How often are METARs taken? At what times?
METARs are taken hourly between 55 to 59 minutes past the hour
335
At what times to METAR observations include "6-hourly observations?"
0000, 0600, 1200, 1800 UTC
336
At what times to METAR observations include "3-hourly observations?"
0300, 0900, 1500, 2100 UTC
337
What is the difference between a METAR and SPECI?
SPECI (Aviation Selected Special Weather Report) is the other routine, unscheduled observation issued when critical data changes
338
What is a METAR?
A METAR is a routine scheduled observation or primary observation code used by the United States to satisfy requirements for reporting surface meteorological data
339
What is a LOCAL?
Aviation Selected Local Weather Report (LOCAL) — LOCALs are taken in support of aircraft operations are encoded in METAR format. When taken and disseminated to agencies other than ATC, the contents are established locally and documented in base/host unit support plans, local weather support agreements or standard operating procedures.
340
Differentiate between a METAR, SPECI, and LOCAL
METAR: hourly scheduled observation
SPECI: special, unscheduled observation whenever critical data has changed
LOCAL: single element observations that contain the time and ALSTG. When ATC does not have access to real- time ALSTG’s, weather personnel will disseminate an ALSTG LOCAL observation at an interval not to exceed 35 minutes when there has been a change of 0.01 inches of mercury or more.
341
What are the two major sections of a METAR/SPECI?
The body and the remarks
342
What are the 2 types of report modifiers and what do they mean?
COR: a corrected METAR or SPECI is transmitted
AUTO (AO1/AO2): fully automated report with no human intervention
343
How is wind speed displayed on a METAR?
True winds are displayed with no delineating line (/) separating wind direction and velocity. Wind speed is displayed on a 2-minute average. Variable wind shows a “V” between variations; gusts are preceded by a “G” followed by the speed. Calm winds are expressed with zeros in the wind group.
344
What is RVR?
Runway Visual Range (RVR) is reported whenever the prevailing visibility is less than or equal to 1 SM (1600 m) and/or when RVR for the designated instrument runway is less than or equal to 6000 ft (1500 m)
345
How far out does present weather address? What about weather in the vicinity?
Present Weather addresses the weather occurring within 5 SM
Weather occurring in the vicinity (VC) of the station (between 5 and 10 SM)
346
What does VV mean?
Vertical visibility
347
What 3 categories of data can be included in the remarks section?
(1) Manual and Automated remarks, (2) Plain language remarks, and (3) Additive data and Maintenance remarks.
348
What is sea level pressure measured in?
Hectopascals (hPa) but 1 hectopascal equals 1 millibar (mb)
349
A METAR is a normally scheduled __________ airfield observation taken between __________ and __________ minutes past the hour.
hourly; 55; 59
350
The two types of routine weather observation reports are the
METAR and SPECI.
351
A(n) __________ is an unscheduled observation containing all the data elements found in a METAR whenever critical data have changed from the previous observation.
SPECI
352
The two sections that make up a METAR are the __________ section and the __________ section.
Body; Remark
353
Definitions for the particular weather phenomena abbreviations can be found in Chapter 10 of __________.
AFMAN 15-111
354
What is a TAF? How long are they good for?
A Terminal Aerodrome Forecast (TAF) is an airport forecast for a specific period (usually 30 hours, but in some cases could be 24 hours). It contains forecasts of wind, visibility, weather/obstructions, sky coverage, icing, turbulence, minimum altimeter settings, and any pertinent remarks.
355
What does a visibility code of "9999" indicate?
A visibility code of “9999” indicates 7 statute miles visibility or greater is forecast, i.e., unlimited visibility
356
How is visibility reported on a TAF?
Forecast prevailing visibility is reported in meters and rounded down to the nearest reportable value. (CONUS civil stations report visibility in statute miles.)
357
How is wind shear reported on a TAF?
WS and a 3-digit height in hundreds of feet AGL
358
How is icing reported on a TAF?
6 digits
1st digit: If non-thunderstorm, the icing group follows the cloud group and is prefixed by the number 6
2nd: indicates the type and intensity of icing
3/4/5th: base of the icing layer in hundreds of feet AGL
6th: depth of the icing layer in thousands of feet
359
How is turbulence forecasted on a TAF?
6 digits
1st: the turbulence code uses the number 5 and follows the clouds
2nd: intensity
3/4/5th: determine the base limit of the turbulence layer in hundreds of feet AGL.
6th: determines the turbulence layer depth in thousands of feet. Add this value to the base height to determine the top limit of the turbulence conditions.
360
How are forecast minimum altimeter settings displayed?
only found in military forecasts. They begin with QNH (minimum), followed by four digits indicating the setting in inches and hundredths of Hg, and end with INS (inHg).
361
How are forecast temperatures displayed on a TAF?
are routinely found only in military TAFs. They are located on the last line, following the minimum altimeter, beginning with the designator TX for the maximum forecast temperature followed by TN for the minimum forecast temperature.
362
What does BECMG mean on a TAF?
BECMG means “becoming” or a “gradual change” in meteorological conditions starting from the first time listed and fully changed by the last time listed
363
What does TEMPO mean on a TAF?
TEMPO represents a temporary condition. Note that only the temporary changing conditions are included in TEMPO groups. TEMPO forecasts do not supersede previous forecast for their valid time.
364
What does TX and TN mean?
TX: maximum temperature
TN: minimum temperature
365
What does FM mean?
FM means “from” and indicates a rapid weather change where all data groups in the previous lines are superseded.
366
What does PROB mean?
Civilian forecasts also use PROB (probable). PROB40 represents a 40% probability or chance of conditions occurring
367
What does AMD mean?
An Amended Aerodrome Forecast (AMD) is issued because the previous version is no longer representative of the current or expected weather. The amended TAF supersedes the previous TAF.
368
What is the minimum sky coverage constituting a ceiling?
c. 5/8 to 7/8
369
From the TAF shown, what is the worst forecast ceiling for KDLF for 2000Z?
c. 1000 feet
370
Using the TAF shown, what are the highest forecast winds for KEND at 030800Z?
c. 200° at 10 knots
371
Using the TAF shown, what is the lowest altimeter setting for KCBM at 1500Z?
b. 29.98
372
What is a Terminal Aerodrome Forecast (TAF)?
a. An airport forecast for a specific period used to determine VFR or IFR flight plan requirements
373
Using the TAF shown, what would be the lowest visibility forecast, in meters, with an ETA of 2030Z at KGRK?
b. 6000
374
Using the TAF shown, when is the lowest ceiling forecast for KRND?
d. 1300Z-1500Z on the 7th
375
What forecasts do not supersede previous forecasts for their valid time?
a. TEMPO
376
What kind of weather does a TAF forecast?
the WORST projected weather
