Weather Review Flashcards

Weather Topics for the Charter Pilot (227 cards)

1
Q

Fill in the blank:

An abrupt change in wind speed or direction is a ______.

A

Wind Shear

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2
Q

What are the seven (7) characteristics of Microbursts?

A
  1. Wind intensify for about 5 minutes after ground contact
  2. Dissipates from 10-20 minutes after ground contact
  3. Spreads in all directions after ground contact in a violent horizontal vortex
  4. Can occur in both wet and dry atmospheres
  5. Can occur in families (there maybe more than one)
  6. Can have a horizontal wind speed difference of 50 - 100 kts
  7. Can have vertical speeds in excess of 3,000 fpm
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3
Q

What are the three (3) Windshear Recover steps?

A
  1. Max power
  2. Pitch up to stick shaker/stall warning (max performance)
  3. Do not change configurations
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4
Q

Ice can be found in what two conditions?

A
  1. Visible moisture
  2. +50 to -200C
    * Usually +2 to -100C
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5
Q

Geographically, the worst icing conditions can be found where?

A
  • Downwind of mountainous terrain
  • Adiabatic cooling created lifting action
  • Downwind of the Great Lakes region
  • Large amounts of moisture
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6
Q

What is the FAA definition of “Known Icing Conditions”?

A

Atmospheric conditions in which the formation of ice is observed or detected in flight.

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7
Q

What is the FAA definition of “Forecast Icing Conditions”?

A

Environmental conditions expected by a National Weather Service or an FAA-approved weather provider to be conducive to the formation of inflight icing on aircraft.

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8
Q

What are six (6) Rime Ice characteristics?

A
  1. Small supercooled water droplets that freeze on contact
  2. Most common form of ice
  3. Milky or opaque in appearance (air bubbles)
  4. Often found in Stratus clouds and smooth air
  5. Relatively brittle
  6. Usually limited to a 3,000’ vertical area
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9
Q

What are characteristics of Clear Ice?

A
  1. A collection of large, close to freezing water droplets that will flow back on the wing before freezing
  2. Clear, hard, glossy, heavy and very difficult to remove
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10
Q

What does Freezing Rain indicate?

A

Warmer temperatures above.

Therefore, climb if able to warmer temperatures.

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11
Q

What do Ice Pellets indicate?

A

Freeing rain at higher altitudes.

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12
Q

Define:

Trace Ice

A

Barely perceptible, rate of accumulation is slightly greater than sublimation.

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13
Q

Define:

Light Ice

A

May be a problem if the flight is prolonged (over 1 hour), occasional use of deice/anti-ice removes accumulation.

Does not present a problem if deice/anti-ice equipment is used.

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14
Q

Define:

Moderate Ice

A

Short encounters become potentially hazardous, use of deice/anti-ice or flight diversion is necessary.

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15
Q

Define:

Severe Ice

A

The rate of accumulation is such that deice/anti-ice equipment fails to reduce or control the hazard. Immediate flight diversion is necessary.

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16
Q

Fill in the blank:

Any runway that is not dry is considered to be ______.

A

wet

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17
Q

Fill in the blank:

A dry runway has ______.

A

no visible moisture, to include:

  • standing water
  • ice
  • snow
  • slush
  • or frost of any form
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18
Q

Fill in the blank:

Land And Hold Short Operations (LAHSO) not authorized on ______ runways.

A

wet

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19
Q

Braking action reports are:

A
  1. Good
  2. Goot to Medium
  3. Medium
  4. medium to Poor
  5. Poor
  6. Nil*

*Note: you should never hear “NIL” – the airfield would be closed!

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20
Q

Fill in the blank:

The Jet Stream is normally found ______.

A

near the upper limit of the troposphere.

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21
Q

What are the characteristics of Troposphere?

A
  • from the surface to ~65,000 feet at the Equater
  • ~20,000 feet at the poles
  • decreasing temperature with height
  • water vapor (weather)
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22
Q

Define:

Tropopause

A

Boundary layer between the Troposphere and the Stratosphere.

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23
Q

Fill in the blank:

Magnitude of wind shear is greater on the ______ side of the Jet Stream.

A

Polar

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24
Q

What is AWOS?

A

Automated Weather Observing System

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25
What weather parameters are provided by **AWOS-A**?
Only reports altimeter.
26
What weather parameters are provided by **AWOS-1**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude
27
What weather parameters are provided by **AWOS-2**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * **Visibility**
28
What weather parameters are provided by **AWOS-3**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * **Visibility** * **Cloud/Ceiling**
29
What weather parameters are provided by **AWOS-3 P**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * Visibility * Cloud/Ceiling * **Precipitation**
30
What weather parameters are provided by **AWOS-3 T**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * Visibility * Cloud/Ceiling * **Thunderstorm**
31
What weather parameters are provided by **AWOS-3 P/T**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * Visibility * Cloud/Ceiling * **Precipitation** * **Thunderstorm/lightning**
32
What weather parameters are provided by **AWOS-4**?
* Altimeter * Wind * Temperature * Dew point * Density Altitude * Visibility * Cloud/Ceiling * Precipitation * Thunderstorm/lightning * **Precipitation Occurance, type, accumulation** * **Freezing rain** * **Thunderstorms** * **Runway surface conditions**
33
What is **ASOS**?
**A**utomated **S**urface **O**bservation **S**ystem ## Footnote More sophisticated than AWOS -- provides info for METAR and TAFs
34
Maximum AWOS/ASOS ceiling and visibility
12,000 feet 10 statute miles
35
What is **METAR**?
**MET**eorological **A**viation **R**outine weather report ## Footnote Terminal weather **_observation_** Issued 5 minutes before the hour
36
A TAF is?
**T**erminal **A**erodrome **F**orecast * 24-hour forecast * Issued 4x day * 00Z * 06Z * 12Z * 18Z * Predicted weather w/in 5sm of the airport
37
What is the **Ceiling**?
Height above the surface (AGL) of lowest layer of clouds that are Broken, Overcast, Obscured and not thin or partial.
38
What is **Virga**?
Precipitation that evaporates before reaching the ground. * Air mass below the cloud is very dry * Indicates strong downdrafts w/possible moderate or greater turbulence
39
Is AWOS without visibility still an authorized weather source for 135?
No, OPSPEC C077 requires ceiling **_and_** visibility
40
TAF & METAR Abbreviations: * NSW * BL * BC * MI * PR * DR * GR
* **NSW** - No Significant Weather * **BL** - Blowing * **BC** - Patches * **MI** - Shallow * **PR** - Partial * **DR** - Drifting * **GR** - Hail
41
More TAF and METAR Abbreviations * SG * GS * BR * FG * FU * DU * PY * SA * FC
* **SG** - Snow Grains * **GS** - Small hail/snow pellets * **BR** - Mist (\>5/8 sm) * **FG** - Fog (\<5/8 sm) * **FU** - Smoke * **DU** - Dust * **PY** - Spray * **SA** - Sand, Sandstorm, Dustorm * **FC** - Funnel Cloud
42
What is the **Standard Atmosphere**?
* 29.92 inches/1013 hectopascals * 150C at Sea Level (590F)
43
What is Troposphere Standard Temperature lapse rate?
40 F/thousand feet (3.57) 6.50 C/thousand meters, ~20C/1000 feet
44
How is **Light Turbulence** defined inside the aircraft?
* Occupants may feel a slight strain against seat belts or shoulder straps. * Unsecure objects may be displaced slightly. * Food service may be conducted and little or no difficulty is encountered in walking.
45
How is **Moderate Turbulence** defined inside the aircraft?
* Occupants feel definite strains against seat belts or shoulder straps * Unsecured objects are dislodged * Food service and walking are difficult
46
How is **Severe Turbulence** defined inside the aircraft?
* Occupants are forced violently against seat belts or shoulder straps * Unsecured objects are tossed about * Food Service and walking are impossible
47
How is **Severe Turbulence** defined based on its impact on an aircraft?
* Aircraft is violently tossed about and is practically impossible to control * May cause structual damage
48
What is an AIRMET (WA)?
**AIR**man's **MET**eorological Information * Weather of interest to all pilots, but hazardous to aircraft having limited capabilites or non-instrumented rated pilots * Less severe than SIGMET * Moderate: icing/turbulence/\>30kts winds, IFR, Mountain obscuration * 4x day, every 6 hours
49
What is an **AIRMET ZULU**?
Icing and freezing level data
50
What is an **AIRMET TANGO**?
Turbulence, strong surface winds, and wind shear.
51
What is an **AIRMET SIERRA**?
Instrument flight rules and mountain obscuration.
52
What is a **SIGMET (WS)**?
SIGnificant METeorological information Serious weather concerning the safety of ALL aircraft * Sever and extreme turbulence or CAT * Severe icing * Dustorms, sandstorms, volcanic ash with vis \< 3 miles
53
What is a **CONVECTIVE SIGMET (WST)**?
Severe thunderstorms, tornadoes, heavy precipitation, hail and high surface winds.
54
What is a SEVERE WEATHER FORECAST ALERTS (AWW)?
Preliminary messages issued to alert that a Severe Weather Bulletin is being issued * Define areas of severe thunderstrorms or tornadoes * Unscheduled
55
What is a Center Weather Advisory (CWA)?
Unscheduled inflight, flow control, ATC, and aircrew advisory * Unscheduled * Supplements an existing SIGMET or AIRMET
56
What is **HIWAS**?
**H**azardous **I**nflight **W**eather **A**dvisory **S**ervice
57
What is an Aviation Area Forecast (FA)?
* Forecast of general weather conditions over a large area of Alaska, Hawaii, and the Caribbean. * Can be used as a forecast for airports that do not have TAF * Issued 3x a day * 12-hour forecast, followed by a 6-hour outlook * Has been discontinued for the continental US * Replaced by the GFA Tool found at www.aviationseather.gov
58
How is **Rime Ice** defined in aviation?
* A collection of very small, supercooled water droplets that freeze on contact. * The most common form of aviation icing * Milky or opaque due to trapped air bubbles * Stratus clouds and smooth air
59
How is **Clear Ice** defined in aviation?
* Hard, glossy, heavy and difficult to remove * Rapid build-up * Found in large cumulus clouds and turbulence
60
How is **Freezing Rain** defined in aviation?
* Indicates warmer temperatures above * The _most severe form of icing_
61
What is the rule on **taking off during ground icing** conditions?
No Pilot may take off in an aircraft with frost, ice or snow adhering to any rotor blade, propeller, windshield, wing, stabilizing or control surface, powerplant, instrument -- **the clean aircraft concept.**
62
What is the **Tropopause**?
The boundary between the Troposphere and the Stratosphere where temperature stops decreasing with altitude. ## Footnote Altitude varies between poles and equator.
63
Why does temperature in the stratosphere's increase with altitude above its isothermal layer?
Because the Ozone layer sits above the stratosphere. The ozone layer absorbs UV rays which cause the stratosphere to heat up.
64
What is **radiation**?
Anything with a temperature above absolute zero (-273 C) radiates heat energy in the form of electromagnetic waves. ## Footnote As heat increases, wavelength decreases. The Sun emits short wave radiation, known as insolation, and the earth emits longwave radiation, known as terrestrial radiation. Heat transfer through radiation can occur in a vacuum.
65
What is **convection**?
The transfer of heat through movement in a body. ## Footnote The earth's surface heats the air, which in turn decreases in pressure and rises. As it cools it travels horizontally, known as advection. It then sinks. Convection and advection together create circulation.
66
What is **conduction**?
The transfer of heat through contact. ## Footnote The earth's surface is heated by insolation from the sun which then heats the air on the surface through conduction. Air is a poor conductor so only the air close to the surface is heated. This is why temperature decreases with altitude close to the earth.
67
Less than half of **solar radiation** from the sun is **absorbed** by the earth's surface. Where **is the rest lost**?
Scattering by airborne particles and reflection from the ground and cloud tops.
68
What is the **greenhouse effect**?
Terrestrial radiation from the earth is absorbed by water and carbon dioxide molecules in the atmosphere and radiated back to the surface.
69
What is an **isotherm**?
A line on a weather map joining two places of the same temperature.
70
What is a **diurnal variation**?
The change of temperature over 24 hours. ## Footnote Over the ocean, it is usually 10C due to the high specific heat of the water. Deserts can be around 200C. Wind can mix up the air and reduce diurnal variation compared to calm conditions. Cloud cover prevents heat transfer to and from the surface, thus reducing diurnal variation.
71
What is an **isobar**?
A line on a weather map joining places of equal pressures.
72
What is **QNE**?
Aeronautical "Q code" for Standard Pressure Altitude setting in your altimeter's Kollsman window. ## Footnote 29.92 inHg/1013.25 Mb for a standard atmosphere.
73
In what **layer of the atmosphere** are **most of the water vapor, clouds, and weather** found?
The Troposphere
74
What three atmospheric factors affect **density**?
1. **Pressure** and density are **directly** related. 2. **Temperature** and density are **inversely** related. 3. **Humidity** and density are **inversely** related.
75
# True or False: Increased Density Altitude improves aircraft performance.
False ## Footnote Increased Density Altitude (higher altitude) degrades aircraft performance. Higher Density Altitude (less dense air) decreases aircraft performance.
76
What **three effects** cause local **air pressure to change**?
1. The movement of pressure systems. 2. The change in intensity of pressure systems. 3. The expansion and contraction of the atmosphere as it heats and cools(semi-diurnal variation).
77
What is **QNH**?
The true sea level pressure. ## Footnote When set on a subscale it will read actual elevation AMSL. Area QNH is the average for a given area and will not differ from an adjoining area or local QNH by more than 5 HPA
78
What will an altimeter read when flying level towards low pressure?
It will read as if it were in a climb. ## Footnote *"High to Low, look out below"*
79
What does **adiabatic** mean?
A temperature change due to a change in pressure.
80
What is a **turbulence inversion**?
Winds at low level may cause adiabatic expansion and cooling due to mixing. If the lower layer becomes cooler then an inversion forms.
81
What is a **subsidence inversion**?
As a column of air subsides, the top of the column undergoes greater heating and compression than the bottom. This creates an inversion.
82
What is a **surface inversion**?
The air close to the earth's surface is cooled at night by conduction. Greatest at dawn.
83
What is a **Frontal inversion**?
The boundary of two masses can become an inversion as Warm air is lifted by cool air.
84
What is Atmospheric **stability?**​
When a parcel of air is lifted and its temperature becomes less than the surrounding environment and sinks once the lifting force is removed.
85
What is Atmospheric ​**instability?**
When a parcel of air is lifted and its temperature becomes more than the surrounding environment and continues to rise once the lifting force is removed.
86
What is **conditional stability** in the atmosphere?
A state of instability that depends upon whether or not the rising air is saturated. Conditional stability occurs when the environmental lapse rate is between the moist and dry adiabatic rates. The atmosphere is normally in a conditionally unstable state
87
What are the **lapse rates** for: * Dew point? * Dry air? * Saturated air? * ISA?
* Dew Point: 0.6oC per 1000' * Dry Air: 3oC per 1000' * Saturated Air: 1.5oC per 1000' * ISA: 2oC per 1000'
88
What is **relative humidity**?
The ratio of water in a sample of air compared to its water volume at saturation. ## Footnote Relative humidity = actual mass of water vapor \ mass of water vapor at saturation.
89
What is **latent heat**?
The heat added to change a substance to a higher state and released, to change to a lower state. ## Footnote There is no change in temperature, just state. Lower - Solid, liquid, gas - higher.
90
How can you **mathematically determine** the base of a **cloud base**?
(Surface Temperature - Surface Dew Point) divided by 2.4. The answer is in thousands of feet.
91
What is a **Foehn** (or Föhn) **Wind?**
The warm dry air on the lee slide of a mountain. Humid air is forced to rise over a mountain forming cloud as it cools adiabatically. Latent heat is released by the process of condensation and carried with the air down the lee side of the mountain as warm dry air.
92
In wind, what do the terms **veer** and **back** mean?
* Veering wind changes in a **clockwise** direction. * Backing wind changes in a **counterclockwise** direction.
93
What is the difference between a **squall** and a **gust**?
* Gusts are a sudden increase in wind lasting a **short period of time**. * Squalls are a sudden increase of wind of at least 16 knots, last for **at least one minute** and can reach up to 22 knots.
94
Describe the **pressure gradient force**.
The tendency for air to flow from high to low pressure across isobars.
95
What is the **Coriolis effect**?
In the Northern Hemisphere, the earth's rotation causes air to deflect to the right. The deflection is greatest at the poles and nil at the equator. The stronger the wind speed the greater the deflection. ## Footnote The deflection is opposite (left) in the Southern Hemisphere. *Toilets flush "backward" in Australia...*
96
What is **Buy Ballots Law**?
With your back to the wind in the northern hemisphere, the atmospheric low pressure is on your left, high to the right. ## Footnote Opposite in the southern hemisphere.
97
What are **geostrophic** and **gradient winds**?
* Geostrophic winds flow parallel to **straight isobars**. * Gradient winds flow parallel to **curved isobars**.
98
What is the **friction layer**?
The lower 3000' of the atmosphere. ## Footnote Wind speeds reduce by ~2/3 over land and ~1/3 over the sea. Reduction in speed reduces the Coriolis effect and winds tend to veer compared to winds aloft. 30 degrees over land and 10 degrees over water due to reduced friction. Winds aloft tend to flow parallel to isobars. Surface winds flow across isobars from high to low pressure.
99
How are land and sea **breezes created**?
The breeze flows towards the hotter of the two to replace the rising air. As the land heats and cools quicker than the sea (the sea has a high specific heat) it is common to have a sea breeze during the day and land breeze night.
100
What causes **katabatic** and **anabatic** winds?
* Anabatic - Air on a mountainside is **heated** by conduction, density reduces and rises up the hill. * Katabatic - Air on a mountainside is **cooled** by conduction density increases and sinks down the hill.
101
What **clouds** form in the **lower étage** (SFC - 6,500')?
* Stratocumulus * Stratus * Cumulus
102
What **clouds** form in the **middle étage** (6,500-25,000')?
* Altocumulus * Altostratus
103
What **clouds** form in the **high étage** (10,000 - 60,000')?
* Cirrus * Cirrocumulus * Cirrostratus ## Footnote *Note: étage elevation is lower at the poles, higher at the equator.*
104
What are **castellanus (or castellatus) clouds**?
Clouds of a turret or cumuliform shape from a common base. ## Footnote Generally associated with altocumulus and indicates instability.
105
The type of clouds formed depends on if the atmosphere is stable or unstable, and what type of lifting mechanism is driving it. What are **four different types of lifting mechanisms**?
1. **Convection** - warm air rises + unstable atmosphere = Cu. If vertical development continues then = Cb. 2. **Convergence** - the center of low pressure creates lift 3. **Orographic** uplift - Mountain waves 4. **Frontal** - warm air forced to rise over cooler air as fronts move
106
What does **CAVOK** mean?
**C**lear **A**nd **V**isibility **OK** ## Footnote No significant weather, visibility greater than 10km, and ceilings greater than 5,000'.
107
What are **NSC** and **NSW**?
* NSC: **No Significant Cloud** * NSW: **No Significant Weather** ## Footnote NSC - no cloud below 5000’ AGL or highest 25nm MSA; whichever is greater and no cumulonimbus or towering cumulus at any height; NSW - no Mist, Dust, Dust storm, Drizzle, Funnel Clouds, Fog, Smoke, Hail, Small Hail Pellets, Haze, Ice Pellets, Dust Devils, Rain, Sand, Snow Grains, Snow Squalls, Sand storm, Unknown Precipitation Type (from weather sensor), Volcanic Ash.
108
When a forecast has **GOOD** or **Unrestricted** **visibility** what is its range?
Greater than 10nm.
109
What are the weather codes for: * Mist * Dust * Duststorm * Drizzle * Funnel Clouds * Fog * Smoke * Hail
* BR: Mist * DU: Dust * DS: Duststorm * DZ: Drizzle * FC: Funnel Clouds * FG: Fog * FU: Smoke * GR: Hail
110
What are the weather codes for: * Small Hail * Pellets * Haze * Ice Pellets * Dust Devils * Rain Sand * Snow Grains * Snow Squalls * Sandstorm * Unknown Precipitation Type (from weather sensor) * Volcanic Ash
* GS: Small Hail Pellets * HZ: Haze * PL: Ice Pellets * PO: Dust Devils * RA: Rain * SA: Sand * SG: Snow Grains * SN: Snow SQ Squalls * SS: Sandstorm * UP: Unknown Precipitation Type (from weather sensor) * VA: Volcanic Ash
111
When is a **SPECI** issued?
**SPECI**al weather reports can be issued at any time to update the METAR for: * Rapidly changing weather conditions * Aircraft mishaps * Other critical information
112
How is the **passage of a cold front** evident?
A **drop in temperature** along with changes in **air pressure** and prevailing **winds**.
113
How is the **passage of a warm front** evident?
Air noticeably **warmer** and more **humid**.
114
What is a **warm front**?
Warm air rising over a cold layer forming a sloping layer in the direction of movement. ## Footnote Warm air is generally stable resulting in Stratiform clouds and rain from nimbostratus. The approach of a warm front is evident by high-level clouds then mid-level clouds and eventually nimbostratus clouds.
115
What is an **occluded front**?
A cold front that catches up to a warm front.
116
What **weather** is associated with an **occluded front**?
* Both warm and cold front weather * Extensive clouds and widespread rain * Embedded thunderstorms
117
What is a **quasi-stationary** front?
A Front that is moving at less than five knots. ## Footnote On a synoptic chart, a front that has not moved from the last synoptic chart (three/six hours) *aka: Stationary Front*
118
What is the **Intertropical Convergence Zone**?
The zone (normally) over the equator between the northeast and southeast trade winds converge. ## Footnote Location varies with seasons. *Trivia: aka: "The Doldrums"*
119
What is a **low-pressure** system?
An area of low pressure (as compared to the area surrounding it). ## Footnote A low-pressure system is associated with: Convection Instability Clouds and rain Visibility is good Wind circulates counterclockwise in the northern hemisphere
120
What is a **high-pressure** system?
An area of high pressure (as compared to the area surrounding it). ## Footnote A high-pressure system is associated with: Clear skies Dry air Visibility is good Wind circulates clockwise in the northern hemisphere
121
What is a **Col**?
A region of slightly elevated pressure between two anticyclones (Highs).
122
What are **streamlines**?
They depict surface winds (2m above the surface) on a streamlines chart.
123
How strong is a **gale force** wind?
34-47 knots
124
What is **fog**?
A cloud at ground level through which visibility is less than 3 miles with relative humidity near 100%.
125
What is the **life cycle** of a **thunderstorm**?
1. Cumulus stage. 2. Mature stage 3. Dissipating stage
126
What are the **different types** of **thunderstorms**?
1. Single Cell 2. Multicell (cluster and line) 3. Supercell
127
What **hazards** are associated with **thunderstorms**?
* Heavy rain * Hail * Icing * Electrical interference * Lightning * Severe turbulence
128
What are the **three** **conditions** required for **Dust storms** to form?
1. A source of dust 2. A mechanism of uplift 3. An unstable environment to keep the dust aloft
129
What are **jet streams**?
Fast moving narrow currents of air found near the tropopause. * Characterized by strong horizontal wind shear * Wind speeds may reach 150 kt * Flow west to east
130
What is **wind shear**?
Change in wind velocity and/or direction -- usually in the vertical.
131
What is a **low-level jet stream**?
Common in the Great Plains and Eastern US. As the name implies, it is a fast-moving ribbon of air in the low levels of the atmosphere. ## Footnote It can rapidly transport Gulf moisture and warmer temperatures to the North at speeds ranging from 25 to over 70 knots.
132
What is **turbulence**?
Caused by the relative movement of disturbed air through which an aircraft is flying. ## Footnote Its origin may be thermal or mechanical and it may occur either within or clear of cloud.
133
What is **hoar** frost?
Occurs when a sub-zero surface comes into contact with moist air. ## Footnote Hoar frost may form on the upper or lower surface of the wings at ambient temperatures well above the freezing point due to the cold soaked fuel in the wing tanks.
134
What is **rime ice**?
Formed when small supercooled water droplets freeze on contact with a surface that is at a sub-zero centigrade (Celcius) temperature. ## Footnote Because the droplets are small, they freeze almost instantly creating a mixture of tiny ice particles and trapped air. The ice deposit formed is **rough** and **crystalline** and **opaque**. Because of its crystalline structure, rime ice is **brittle**.
135
What is **clear ice**?
* Clear, or Glaze, ice is widely considered to be the most dangerous form of icing. * Water drops are carried above the freezing level, they become supercooled. * A smooth, hard, glossy, and transparent covering of ice over the wing surface called clear ice. * Clear icing is most significant in the range of 0c to -20c. * Ice accretion can be very fast in the highest concentrations of supercooled water.
136
What is **carburetor icing**?
Ice formed in the venturi of a carburettor as intake air is cooled by fuel evaporation and lossof pressure. ## Footnote Carburettor ice can cause engine failure if not detected early enough and removed by use of carburettor heat. Carburettor ice is possible over a wide range of outside air temperatures (up to 40 deg C), but humidity must be relatively high.
137
What type of icing is associated with **Cirrus clouds**?
**No icing** as the cloud consists of ice crystals.
138
What type of icing is associated with **Cirrostratus clouds**?
**No icing** as the cloud consists of ice crystals.
139
What type of icing is associated with **Cirrocumulus clouds**?
**Rare** as the cloud consists mainly of ice crystals.
140
What type of icing is associated with **Altostratus clouds**?
**Light rime ice** may occur in this type of cloud as it consists mainly of supercooled water droplets. ## Footnote Prolonged flight in altostratus may produce a large build-up of rime ice, which could prove hazardous to an airplane not equipped to remove the ice. Clear ice is a possibility in thick altostratus.
141
What type of icing is associated with **Altocumulus clouds**?
If the cloud is thin, **light rime ice** may occur in the same way as it does in altostratus. ## Footnote There is nearly always some turbulence associated with altocumulus and this enables the cloud to support larger supercooled water drops.
142
What type of icing is associated with **Nimbostratus clouds**?
As supercooled rain is often present in this cloud type, ice is usually **clear to mixed**.
143
What type of icing is associated with **Cumulus clouds**?
*_Small_* cumulus clouds will nearly always be at a temperature above freezing, so **no ice** will form in them. However, in *_large_* cumulus clouds, **clear ice** may occur up to about 5000 ft above the freezing level. Above this altitude, rime ice will occur.
144
What type of icing is associated with **Cumulonimbus clouds**?
Large supercooled water drops will occur at, and above the freezing level. From the freezing level up to where the temperature reduces to approximately -15 degrees C, clear ice will occur. Above this altitude, rime ice will occur up to the level where ice crystals predominate.
145
What are **microbursts**?
* These are strong concentrated downbursts of air from the base of a convective cloud. * They are often associated with squall lines and thunderstorm activity and may also be associated with virga. * The typical life cycle of a microburst from ground contact to dissipation is around 15 minutes. * An aircraft encountering the outflow from a microburst at low-level will initially experience increasing headwind and improved performance followed by decreasing headwind then downdraft and sink followed by increasing tailwind. * These effects can cause a large airspeed loss and severely degraded climb performance. In some cases, the velocity of the downburst can exceed the climb capability of the aircraft resulting in ground contact.
146
Is the **tropopause** a **continuous layer around the world**?
**No**. The tropopause is not a continuous surface from the equator to the poles but is broken and uneven and there may even be more than one tropopause above a particular location.
147
What is **clear air turbulence (CAT)**?
A long narrow meandering current of high-speed winds near the tropopause blowing from a generally westerly direction and often exceeding a speed of 250 miles (402 kilometers) per hour.
148
What are the **four** main **types of fog**?
1. Radiation * Cloudless night * Moist air in contact with the surface cools below the dewpoint 2. Advection * Warm moist air flows across a colder surface 3. Frontal * Post front passage clouds extend to the surface 4. Steam * Very cold air flows across warm water
149
The **wind direction** in an **ATIS** is reported reference True or Magnetic North?
Magnetic North ## Footnote Tower Winds are also Magnetic.
150
The **wind direction** in a **METAR** is reported reference True or Magnetic North?
True North
151
# Fill in the blank: Every physical process of **weather** is accompanied by, or is the result of, a \_\_\_\_\_\_.
Heat exchange
152
What causes **variations in altimeter settings** between weather reporting points?
Unequal heating of the earth's surface.
153
# Fill in the blank: The **development** of **thermals** depends upon \_\_\_\_\_\_.
Solar heating
154
What primarily causes the difference in wind direction between southwesterly winds at 5,000 feet AGL and southerly surface winds?
**Friction** between the wind and the surface.
155
What causes the **convective circulation** patterns associated with sea breezes?
Cool, dense air moving inland from over the water.
156
A **temperature inversion** would most likely result in which weather **conditions**?
An increase in temperature as altitude is increased.
157
The **most frequent type of ground** or surface-based **temperature inversion** is that which is produced by:
Terrestrial radiation on a clear, relatively still night.
158
What is **dewpoint**?
The temperature to which air must be cooled to become saturated.
159
What does the amount of **water vapor** that air can hold depend on?
Air temperature
160
When will **clouds**, **fog**, or **dew** always form?
Water vapor condenses.
161
What are the **processes** by which **moisture** is **added** to **unsaturated air**?
Evaporation and sublimation.
162
If the **temperature/dewpoint spread is small** and decreasing, and the temperature is 62 degrees F, what **type of weather** is most likely to develop?
Fog or low clouds.
163
The **boundary between two different air masses** is referred to as:
Front
164
What is one of the most easily recognized **discontinuities across a front**?
A change in temperature.
165
What weather phenomenon will always occur when **flying across a front**?
Wind direction
166
Which **weather conditions** should be expected **beneath** a l**ow-level temperature inversion** layer when the relative humidity is high?
Smooth air, poor visibility, fog, haze, or low clouds.
167
What **measurement** can be used to determine the **stability** of the atmosphere?
Actual lapse rate
168
What would **decrease** the **stability** of an air mass?
Warming from below
169
What is a **characteristic** of **stable air**?
Stratiform clouds
170
What **feature** is associated with a **temperature inversion**?
A stable layer of air
171
What are **characteristics** of a **moist, unstable air mass**?
Cumuliform clouds and showery precipitation.
172
What are **characteristics** of **unstable air**?
Turbulence and good surface visibility.
173
A **stable air mass** is most likely to have which **characteristic**?
Poor surface visibility.
174
**Moist**, **stable air** flowing **upslope** can be expected to:
Produce stratus type clouds.
175
If an **unstable air mass** is **forced upward**, what type of **clouds** can be expected?
Clouds with considerable vertical development and associated turbulence.
176
**Steady precipitation** preceding a **front** is an indication of:
Stratiform clouds with little or no turbulence.
177
The **conditions** necessary for the formation of **cumulonimbus** clouds are a lifting action and:
Unstable, moist air.
178
What is the **approximate base** of the **cumulus clouds** if the surface air temperature at 1,000 feet MSL is 70 degrees F and the dewpoint is 48 degrees F:
~7,300 feet MSL. ## Footnote *70o- 48o = 22* *22/3.5 (standard adiabatic lapse rate F) = 6.3* *6300' + 1000' (current elevation) = 7000' MSL*
179
At approximately what altitude above the surface would the pilot expect the base of cumuliform clouds if the surface air temperature is 82o F and the dewpoint is 38o F?
6,300 feet AGL.
180
What does the suffix "**nimbus**," used in naming clouds, mean?
A rain cloud.
181
According to what characteristic are clouds divided into **four families**?
Height range.
182
What **clouds** have the greatest **turbulence**?
Cumulonimbus
183
What is the name of a stationary, **almond- or lens-shaped cloud** that can contain winds exceeding 50 knots?
A lenticular cloud.
184
What type of stationary, lens-shaped cloud often forms at the crests of **standing mountain waves**?
Standing lenticular clouds.
185
What types of **clouds** would indicate **convective turbulence**?
Towering cumulus clouds.
186
Mountain wave turbulence is likely when wind speeds of 40 knots or more are observed blowing in which manner relative to a mountain range?
Across a mountain ridge, and the air is stable.
187
Upon **encountering severe turbulence**, which **flight condition** should the pilot attempt to **maintain**?
* Level wings (roll) * Constant/desired pitch
188
What feature is **normally associated** with the **cumulus stage** of a **thunderstorm**?
Continuous updraft.
189
Which weather **phenomenon** signals the beginning of the **mature stage of a thunderstorm**?
Precipitation beginning to fall.
190
What **conditions** are necessary for the **formation of thunderstorms**?
* High humidity * Lifting force * Unstable conditions
191
During the lifecycle of a **thunderstorm**, which **stage** is characterized predominately by **downdrafts**?
Dissipating
192
# Fill in the blank: **Thunderstorms** reach their **greatest intensity** during the \_\_\_\_\_\_ **stage**.
mature
193
Which **type of thunderstorm** typically presents the greatest hazard to aircraft due to its intensity and severity?
Squall line thunderstorms
194
What is the term for a **narrow, non-frontal band of active thunderstorms** that commonly forms **ahead of a cold front**?
Squall line
195
If there is **thunderstorm activity in the vicinity of an airport** at which you plan to land, which **hazardous atmospheric phenomenon** might be expected on the landing approach?
Wind-shear
196
Which **weather** phenomenon is **always associated** with a **thunderstorm**?
Lightning
197
Where does **wind shear** occur?
At all altitudes, in all directions.
198
When may **hazardous wind shear** be expected?
In areas of: * low-level temperature inversion * frontal zones * clear-air turbulence.
199
A pilot can expect a **wind-shear zone** in a temperature inversion whenever the wind speed at 2,000 to 4,000 feet above the surface is at least:
25 kts.
200
The presence of **ice pellets** **at the surface** is evidence that there:
Is a temperature inversion with freezing rain at a higher altitude.
201
What in-flight **condition** is essential for the formation of **structural icing** on an aircraft?
Visible moisture
202
In which **environment** is **aircraft structural ice** most likely to have the **highest accumulation rate**?
Freezing rain
203
What situations are most **conducive to the formation of radiation fog**?
* Warm, moist air * Over low, flatland areas * Clear, calm nights
204
In which situation is **advection fog** most likely to **form**?
An air mass moving inland from the coast in winter.
205
What **types** of **fog** depend on the **wind** in order to exist?
Advection and upslope fog
206
**Low-level turbulence** can occur **and icing** can become hazardous in which **type of fog**?
Steam fog
207
Which **conditions** result in the formation of **frost**?
The temperature of the collecting surface is at or below the dewpoint of the adjacent air and the dewpoint is below freezing.
208
How will **frost on the wings** of an airplane **affect takeoff performance**?
Frost will disrupt the smooth flow of air over the wind, adversely affecting its lifting capability.
209
Why is frost considered hazardous to flight?
Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability.
210
What is the **recommended distance** to stay clear of **thunderstorms**?
Minimum 20 miles
213
What is an **FA** forecast?
An area forecast. Has been retired for CONUS. It will continue for Alaska, the Gulf of Mexico, Hawaii, and the Caribbean. ## Footnote Replaced by the Graphical Forecast for Aviation (GFA).
214
What is a **Surface Analysis chart**?
It shows low pressures, high pressures, and fronts.
215
What's a **Radar Summary chart**?
It shows precipitation type and intensity, echoes, tops, and movement.
216
What's a **Wind and Temperatures Aloft chart**?
It shows winds and temps at various altitudes. When you see a first number above 4, subtract 5, and add 100 knots to the wind velocity.
217
What's a **Prog chart**?
Significant Weather Prog(nosis) Charts show freezing level, turbulence, VFR/MVFR/IFR. Surface Prog Charts show precip type and intensity, highs/lows, fronts.
218
How are **Wind Shear reports** distributed?
Windshear reports come out only on the ATIS. However, low-level wind shear is reported in an area forecast.
219
What is the difference between **few** clouds, **scattered**, **broken**, and **overcast**?
* Few = 1-2 eights (octals) of the sky covered with clouds. * Scattered = 3-4. * Broken = 5-7. * Overcast = 8.
220
What is **pressure altitude**? **Density altitude**?
* Pressure altitude: the altitude that the altimeter displays when the pressure is set to 29.92. * Density altitude: pressure altitude corrected for nonstandard temperature. When the temperature is higher than standard, the density altitude is higher than pressure altitude.
221
What are **magnetic** **compass errors**?
When the aircraft is accelerated or turned to a new heading, the following two rules apply: 1. ANDS: When on an easterly or westerly heading, in the northern hemisphere, if the aircraft accelerates, it momentarily shows a turn toward the north. If it decelerates, it momentarily shows a turn toward the south. 2. UNOS: When on a northerly heading and a turn towards the east or west is made, the compass will lag. When on a southerly heading, and turning east or west, the compass will lead the actual heading.
222
What are the **entry requirements** for A, B, C, and D airspace?
**Class A**: instrument-rated, ATC clearance, mode C transponder, and two-way radio. **Class B**: private pilot or student with endorsement, ATC clearance, mode C transponder, and two-way radio. **Class C**: radio contact, mode C transponder, two-way radio. **Class D**: radio contact, two-way radio.
223
What do all of the light signals mean (ground/flight)?
_ON GROUND:_ * solid red: stop * flashing red: clear the runway * flashing white: return to starting position at the airport * solid green: cleared for takeoff * flashing green: cleared to taxi * flashing red and green: exercise extreme caution _IN FLIGHT_: * solid red: continue circling, give way to other aircraft * flashing red: airport unsafe, do not land * solid green: clear to land * flashing green: cleared to approach the airport * flashing red and green: exercise extreme caution
224
In a **METAR**, how are clear skies encoded?
* Manual METAR: SKC. * Automated METAR: CLR.
225
When a **TAF** says "**TEMPO**", how long are the conditions expected to last?
Generally, less than an hour.
226
How often are **TAFs generated**? **METARs**? **Area forecasts**?
* TAFs: 0000 UTC, 0600, 1200, 1800. Valid for 24 hours. * METARs: on the hour. No validity period; observation, not forecast. * Area forecast: 3 times daily, good for 18 hours.
227
On a **METAR**, what does **VV005** mean?
Vertical visibility, 500 feet.
228
If you are flying with an altimeter setting of 29.00, and you enter a new area where the recommended altimeter setting is 28.50, but you don't adjust the altimeter, what kind of problems would you have?
The altimeter would read higher than the actual altitude. ## Footnote *"High to Low, look out below"*
229
How does **temperature** affect the **altimeter**?
When the temperature drops, the altimeter reads higher than actual. ## Footnote *Hot to cold, look out below.*