Weather Review Flashcards
Weather Topics for the Charter Pilot
An abrupt change in wind speed or direction is a ______.
Wind Shear
Seven (7) characteristics of Microbursts are?
- Wind intensify for about 5 minutes after ground contact
- Dissipates from 10-20 minutes after ground contact
- Spreads in all directions after ground contact in a violent horizontal vortex
- Can occur in both wet and dry atmospheres
- Can occur in families (there maybe more than one)
- Can have a horizontal wind speed difference of 50 - 100 kts
- Can have vertical speeds in excess of 3,000 fpm
Three Windshear Recover steps are?
- Max power
- Pitch up to stick shaker/stall warning (max performance)
- Do not change configurations
Ice can be found in what two conditions?
- Visible moisture
- +50 to -200C
* Usually +2 to -100C
Geographically, the worst icing conditions can be found where?
- Downwind of mountainous terrain
- Adiabatic cooling created lifting action
- Downwind of the Great Lakes region
- Large amounts of moisture
FAA defines “Known Icing Conditions” as…
Atmospheric conditions in which the formation of ice is observed or detected in flight.
FAA defines “Forecast Icing Conditions” as…
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.
Six (6) Rime Ice Characteristics are…
- Small supercooled water droplets that freeze on contact
- Most common form of ice
- Milky or opaque in appearance (air bubbles)
- Often found in Stratus clouds and smooth air
- Relatively brittle
- Usually limited to a 3,000’ vertical area
Characteristics of Clear Ice are…
- A collection of large, close to freezing water droplets that will flow back on the wing before freezing
- Clear, hard, glossy, heavy and very difficult to remove
What does Freezing Rain indicate?
Warmer temperatures above
Therefore, climb if able to warmer temperatures
What do Ice Pellets indicate?
Freeing rain at higher altitudes.
Trace Ice is…
Barely perceptible, rate of accumulation is slightly greater than sublimation.
Light Ice is…
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.
Moderate Ice is…
Short encounters become potentially hazardous, use of deice/anti-ice or flight diversion is necessary.
Severe Ice is…
The rate of accumulation is such that deice/anti-ice equipment fails to reduce or control the hazard. Immediate flight diversion is necessary.
Any runway that is not dry is considered to be ______
wet
A dry runway has _______
no visible moisture, to include:
- standing water
- ice
- snow
- slush
- or frost of any form
Land And Hold Short Operations (LAHSO) not authorized on ______________ runways.
wet
Braking action reports are:
- Good
- Goot to Medium
- Medium
- medium to Poor
- Poor
- Nil*
*Note: you should never hear “NIL” – the airfield would be closed!
The Jet Stream is normally found…
near the upper limit of the troposphere.
Troposphere is…
- from the surface to ~65,000 feet at the Equater
- ~20,000 feet at the poles
- decreasing temperature with height
- water vapor (weather)
Tropopause is…
Boundary layer between the Troposphere and the Stratosphere
Magnitude of wind shear is greater on the ____ side of the Jet Stream.
Polar
AWOS is…
Automated Weather Observing System
AWOS-A
Only reports altimeter
AWOS-1
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
AWOS-2
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
- Visibility
AWOS-3
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
- Visibility
- Cloud/Ceiling
AWOS-3 P
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
- Visibility
- Cloud/Ceiling
- Precipitation
AWOS-3 T
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
- Visibility
- Cloud/Ceiling
- Thunderstorm
AWOS-3 P/T
- Altimeter
- Wind
- Temperature
- Dew point
- Density Altitude
- Visibility
- Cloud/Ceiling
- Precipitation
- Thunderstorm/lightning
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
ASOS
Automated Surface Observation System
More sophisticated than AWOS – provides info for METAR and TAFs
Maximum AWOS/ASOS ceiling and visibility
12,000 feet
10 statute miles
A METAR is?
METeorological Aviation Routine weather report
- Terminal weather observation
- Issued 5 minutes before the hour
A TAF is?
Terminal Aerodrome Forecast
- 24-hour forecast
- Issued 4x day
- 00Z
- 06Z
- 12Z
- 18Z
- Predicted weather w/in 5sm of the airport
The Ceiling is?
Height above the surface (AGL) of lowest layer of clouds that are Broken, Overcast, Obscured and not thin or partial.
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
Is AWOS without visibility still an authorized weather source for 135?
No, OPSPEC C077 requires ceiling and visibility
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
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
The Standard Atmosphere is…?
- 29.92 inches/1013 hectopascals
- 150C at Sea Level (590F)
What is Troposphere Standard Temperature lapse rate?
40 F/thousand feet (3.57)
6.50 C/thousand meters, ~20C/1000 feet
Light Turbulence is defined as _______ 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.
Moderate Turbulence is defined as _______ inside the aircraft.
- Occupants feel definite strains against seat belts or shoulder straps
- Unsecured objects are dislodged
- Food service and walking are difficult
Severe Turbulence is defined as _______ inside the aircraft.
- Occupants are forced violently against seat belts or shoulder straps
- Unsecured objects are tossed about
- Food Service and walking are impossible
Severe Turbulence is defined as _______ on aircraft.
- Aircraft is violently tossed about and is practically impossible to control
- May cause structual damage
What is an AIRMET (WA)?
AIRman’s METeorological 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
What is an AIRMET ZULU?
Icing and freezing level data
What is an AIRMET TANGO
Turbulence, strong surface winds, and wind shear
What is an AIRMET SIERRA?
Instrument flight rules and mountain obscuration
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
What is a CONVECTIVE SIGMET (WST)
Severe thunderstorms, tornadoes, heavy precipitation, hail and high surface winds
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
What is a Center Weather Advisory (CWA)?
Unscheduled inflight, flow control, ATC, and aircrew advisory
- Unscheduled
- Supplements an existing SIGMET or AIRMET
What is HIWAS?
Hazardous Inflight Weather Advisory Service
Discontinued 1 Jan 2020
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
What is Rime Ice?
- 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
What is Clear Ice?
- Hard, glossy, heavy and difficult to remove
- Rapid build-up
- Found in large cumulus clouds and turbulence
What is Freezing Rain?
- Indicates warmer temperatures above
- The most severe form of icing
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.
What is the Tropopause?
The boundary between the Troposphere and the Stratosphere where temperature stops decreasing with altitude.
Altitude varies between poles and equator.
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.
What is radiation?
Radiation - anything with a temperature above absolute zero (-273 C) radiates heat energy in the form of electromagnetic waves.
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.
What is convection?
The transfer of heat through movement in a body.
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.
What is conduction?
Conduction is the transfer of heat through contact.
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.
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.
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.
What is an isotherm?
A line on a weather map joining two places of the same temperature.
What is a diurnal variation?
The change of temperature over 24 hours.
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.
What is an isobar?
A line on a weather map joining places of equal pressures.
What is QNE?
Aeronautical “Q code” for Standard Pressure Altitude setting in your altimeter’s Kollsman window.
29.92 inHg/1013.25 Mb for a standard atmosphere.
In what layer of the atmosphere are most of the water vapor, clouds, and weather found?
The Troposphere.
What three atmospheric factors affect density?
- Pressure and density are directly related.
- Temperature and density are inversely related.
- Humidity and density are inversely related.
True/False
Increased Density Altitude improves aircraft performance.
False: increased Density Altitude (higher altitude) degrades aircraft performance.
Higher Density Altitude (less dense air) decreases aircraft performance.
What three effects cause local air pressure to change?
- The movement of pressure systems.
- The change in intensity of pressure systems.
- The expansion and contraction of the atmosphere as it heats and cools(semi-diurnal variation).
What is QNH?
QNH is the true sea level pressure. 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
What will an altimeter read when flying level towards low pressure?
It will read as if it were in a climb.
“High to Low, look out below”
What does adiabatic mean?
A temperature change due to a change in pressure.
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.
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.
What is a surface inversion?
The air close to the earth’s surface is cooled at night by conduction. Greatest at dawn.
What is a Frontal inversion?
The boundary of two masses can become an inversion as Warm air is lifted by cool air.
What is Atmospheric stability?
- 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.
- 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.
- Conditional instability is 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
What is Atmospheric instability?
- 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.
What is conditional stability in the atmosphere?
- Conditional instability is 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
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’
What is relative humidity?
The ratio of water in a sample of air compared to its water volume at saturation.
Relative humidity = actual mass of water vapor \ mass of water vapor at saturation.
What is latent heat?
The heat added to change a substance to a higher state and released, to change to a lower state.
There is no change in temperature, just state. Lower - Solid, liquid, gas - higher
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
What is a Foehn (or Föhn) Wind?
Foehn wind is 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.
In wind, what do the terms veer and back mean?
Veering wind changes in a clockwise direction.
Backing wind changes in a counterclockwise direction.
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.
Describe the pressure gradient force.
The tendency for air to flow from high to low pressure across isobars.
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.
The deflection is opposite (left) in the Southern Hemisphere.
Toilets flush “backward” in Australia…
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.
Opposite in the southern hemisphere.
What are geostrophic and gradient winds?
Geostrophic winds flow parallel to straight isobars.
Gradient winds flow parallel to curved isobars.
What is the friction layer?
The lower 3000’ of the atmosphere.
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.
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.
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.
What clouds form in the lower étage (SFC - 6,500’)?
- Stratocumulus
- Stratus
- Cumulus
What clouds form in the middle étage (6,500-25,000’)?
- Altocumulus
- Altostratus
What clouds form in the high étage (10,000 - 60,000’)?
- Cirrus
- Cirrocumulus
- Cirrostratus
Note: étage elevation is lower at the poles, higher at the equator.
What are castellanus (or castellatus) clouds?
Clouds of a turret or cumuliform shape from a common base.
Generally associated with altocumulus and indicates instability.
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?
- Convection - warm air rises + unstable atmosphere = Cu. If vertical development continues then = Cb.
- Convergence - the center of low pressure creates lift
- Orographic uplift - Mountain waves
- Frontal - warm air forced to rise over cooler air as fronts move
What does CAVOK mean?
Clear And Visibility OK
No significant weather, visibility greater than 10km, and ceilings greater than 5,000’.
What are NSC and NSW?
NSC: No Significant Cloud – no cloud below 5000’ AGL or highest 25nm MSA; whichever is greater and no cumulonimbus or towering cumulus at any height;
NSW: No Significant Weather – 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.
When a forecast has GOOD or Unrestricted visibility what is its range?
Greater than 10nm.
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
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
When is a SPECI issued?
SPECIal weather reports can be issued at any time to update the METAR for:
- Rapidly changing weather conditions
- Aircraft mishaps
- Other critical information
How is the passage of a cold front evident?
A drop in temperature along with changes in air pressure and prevailing winds.
How is the passage of a warm front evident?
Air noticeably warmer and more humid.
What is a warm front?
Warm air rising over a cold layer forming a sloping layer in the direction of movement.
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.
What is an occluded front?
A cold front that catches up to a warm front.
What weather is associated with an occluded front?
- Both warm and cold front weather
- Extensive clouds and widespread rain
- Embedded thunderstorms
What is a quasi-stationary front?
A Front that is moving at less than five knots.
On a synoptic chart, a front that has not moved from the last synoptic chart (three/six hours)
aka: Stationary Front
What is the Intertropical Convergence Zone?
The zone (normally) over the equator between the northeast and southeast trade winds converge.
location varies w/seasons
Trivia: aka: “The Doldrums”
What is a low-pressure system?
An area of low pressure (as compared to the area surrounding it).
A low-pressure system is associated with:
Convection
Instability
Clouds and rain.
Visibility is good.
Wind circulates counterclockwise in the northern hemisphere.
What is a high-pressure system?
An area of high pressure (as compared to the area surrounding it).
A high-pressure system is associated with:
Clear skies
Dry air
Visibility is good
Wind circulates clockwise in the northern hemisphere.
What is a Col?
A Col is a region of slightly elevated pressure between two anticyclones (Highs).
What are streamlines?
Streamlines depict surface winds (2m above the surface) on a streamlines chart.
How strong is a gale force wind?
34-47 knots
What is fog?
Fog is cloud at ground level through which visibility is less than 3 miles with relative humidity near 100%.
What is the life cycle of a thunderstorm?
- Cumulus stage.
- Mature stage
- Dissipating stage
What are the different types of thunderstorms?
- Single Cell
- Multicell (cluster and line)
- Supercell
What hazards are associated with thunderstorms?
- Heavy rain
- Hail
- Icing
- Electrical interference
- Lightning
- Severe turbulence
What are the three conditions required for Dust storms to form?
- A source of dust
- A mechanism of uplift
- An unstable environment to keep the dust aloft
What are jet streams?
Jet Streams are 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
What is wind shear?
Change in wind velocity and/or direction – usually in the vertical.
What is a low-level jet stream?
The low-level jet is 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.
It can rapidly transport Gulf moisture and warmer temperatures to the North at speeds ranging from 25 to over 70 knots
What is turbulence?
Turbulence is caused by the relative movement of disturbed air through which an aircraft is flying.
Its origin may be thermal or mechanical and it may occur either within or clear of cloud.
What is hoar frost?
Hoar frost occurs when a sub-zero surface comes into contact with moist air.
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.
What is rime ice?
Rime ice is formed when small supercooled water droplets freeze on contact with a surface that is at a sub-zero centigrade (Celcius) temperature.
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.
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.
What is carburetor icing?
Ice formed in the venturi of a carburettor as intake air is cooled by fuel evaporation and lossof pressure. 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.
What type of icing is associated with Cirrus clouds?
Cirrus: No icing as the cloud consists of ice crystals.
What type of icing is associated with Cirrostratus clouds?
Cirrostratus: No icing as the cloud consists of ice crystals.
What type of icing is associated with Cirrocumulus clouds?
Cirrocumulus: Rare as the cloud consists mainly of ice crystals.
What type of icing is associated with Altostratus clouds?
Altostratus: Light rime ice may occur in this type of cloud as it consists mainly of supercooled water droplets. 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.
What type of icing is associated with Altocumulus clouds?
Altocumulus: If the cloud is thin, light rime ice may occur in the same way as it does in altostratus.
There is nearly always some turbulence associated with altocumulus and this enables the cloud to support larger supercooled water drops.
What type of icing is associated with Nimbostratus clouds?
Nimbostratus (orographic): As supercooled rain is often present in this cloud type, ice is usually clear to mixed.
What type of icing is associated with Cumulus clouds?
Cumulus: 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.
What type of icing is associated with Cumulonimbus clouds?
Cumulonimbus: 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.
What are microbursts?
- Microbursts are strong concentrated downbursts of air from the base of a convective cloud.
- Microbursts 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.
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.
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.
What are the four main types of fog?
- Radiation
* Cloudless night
* Moist air in contact with the surface cools below the dewpoint - Advection
* Warm moist air flows across a colder surface - Frontal
* Post front passage clouds extend to the surface - Steam
* Very cold air flows across warm water
The wind direction in an ATIS is reported reference True or Magnetic North?
Magnetic North
Tower Winds are also Magnetic.
The wind direction in a METAR is reported reference True or Magnetic North?
True North
Every physical process of weather is accompanied by, or is the result of, a:
Heat exchange.
What causes variations in altimeter settings between weather reporting points?
Unequal heating of the earth’s surface.
The development of thermals depends upon:
Solar heating.
The wind at 5,000 feet AGL is southwesterly while the surface wind is southerly. This difference in direction is primarily due to:
Friction between the wind and the surface.
Convective circulation patterns associated with sea breezes are caused by:
Cool, dense air moving inland from over the water.
A temperature inversion would most likely result in which weather conditions?
An increase in temperature as altitude is increased.
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.
What is “dewpoint?”
The temperature to which air must be cooled to become saturated.
The amount of water vapor which air can hold depends on the:
Air temperature.
Clouds, fog, or dew will always form when:
Water vapor condenses.
What are the processes by which moisture is added to unsaturated air?
Evaporation and sublimation.
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.
The boundary between two different air masses is referred to as:
Front
One of the most easily recognized discontinuities across a front is:
A change in temperature.
One weather phenomenon which will always occur when flying across a front is a change in the:
Wind direction.
Which weather conditions should be expected beneath a low-level temperature inversion layer when the relative humidity is high?
Smooth air, poor visibility, fog, haze, or low clouds.
What measurement can be used to determine the stability of the atmosphere?
Actual lapse rate.
What would decrease the stability of an air mass?
Warming from below.
What is a characteristic of stable air?
Stratiform clouds.
What feature is associated with a temperature inversion?
A stable layer of air.
What are characteristics of a moist, unstable air mass?
Cumuliform clouds and showery precipitation.
What are characteristics of unstable air?
Turbulence and good surface visibility.
A stable air mass is most likely to have which characteristic?
Poor surface visibility.
Moist, stable air flowing upslope can be expected to:
Produce stratus type clouds.
If an unstable air mass is forced upward, what type of clouds can be expected?
Clouds with considerable vertical development and associated turbulence.
Steady precipitation preceding a front is an indication of:
Stratiform clouds with little or no turbulence.
The conditions necessary for the formation of cumulonimbus clouds are a lifting action and:
Unstable, moist air.
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.
70o- 48o = 22
22/3.5 (standard adiabatic lapse rate F) = 6.3
6300’ + 1000’ (current elevation) = 7000’ MSL
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.
The suffix “nimbus,” used in naming clouds, means:
A rain cloud.
Clouds are divided into four families according to their:
Height range.
What clouds have the greatest turbulence?
Cumulonimbus.
An almond or lens-shaped cloud which appears stationary, but which may contain winds of 50 kts or more, is referred to as:
A lenticular cloud.
Crests of standing mountain waves may be marked by stationary, lens-shaped clouds known as:
Standing lenticular clouds.
What types of clouds would indicate convective turbulence?
Towering cumulus clouds.
Possible mountain wave turbulence could be anticipated when winds of 40 kts or greater blow:
Accross a mountain ridge, and the air is stable.
Upon encountering severe turbulence, which flight condition should the pilot attempt to maintain?
- Level wings (roll)
- Constant/desired pitch
What feature is normally associated with the cumulus stage of a thunderstorm?
Continuous updraft.
Which weather phenomenon signals the beginning of the mature stage of a thunderstorm?
Precipitation beginning to fall.
What conditions are necessary for the formation of thunderstorms?
- High humidity
- Lifting force
- Unstable conditions
During the lifecycle of a thunderstorm, which stage is characterized predominately by downdrafts?
Dissipating
Thunderstorms reach their greatest intensity during the ___________ stage.
Mature stage
The Thunderstorm types which generally produce the most intense hazard to aircraft are:
Squall line thunderstorms
A non-frontal, narrow band of active thunderstorms that often develop ahead of a cold front is known as a:
Squall line
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 is:
Wind-shear
Which weather phenomenon is always associated with a thunderstorm?
Lightning
Where does wind shear occur?
At all altitudes, in all directions.
When may hazardous wind shear be expected?
In areas of:
- low-level temperature inversion
- frontal zones
- clear-air turbulence.
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.
The presence of ice pellets at the surface is evidence that there:
Is a temperature inversion with freezing rain at a higher altitude.
One in-flight condition necessary for structural icing to form is:
Visible moisture.
In which environment is aircraft structural ice most likely to have the highest accumulation rate?
Freezing rain
What situation is most conducive to the formation of radiation fog?
- Warm, moist air
- Over low, flatland areas
- Clear, calm nights.
In which situation is advection fog most likely to form?
An air mass moving inland from the coast in winter.
What types of fog depend on the wind in order to exist?
Advection and upslope fog
Low-level turbulence can occur and icing can become hazardous in which type of fog?
Steam fog
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.
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.
Why is frost considered hazardous to flight?
Frost spoils the smooth flow of air over the wings, thereby decreasing lifting capability.
What is the recommended distance to stay clear of thunderstorms?
Minimum 20 miles
What was an FA forecast?
FA is an area forecast. Has been retired for CONUS. It will continue for Alaska, the Gulf of Mexico, Hawaii, and the Caribbean.
Replaced by the Graphical Forecast for Aviation (GFA).
What is a Surface Analysis chart?
Surface Analysis Chart shows low pressures, high pressures, and fronts.
What’s a Radar Summary chart?
Radar Summary Chart has precipitation type and intensity, echoes, tops, and movement.
What’s a Wind and Temperatures Aloft chart?
Winds and Temperatures Aloft Chart 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.
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.
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.
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.
What is pressure altitude? Density altitude?
- Pressure altitude is the altitude that the altimeter displays when the pressure is set to 29.92.
- Density altitude is pressure altitude corrected for nonstandard temperature. When the temperature is higher than standard, the density altitude is higher than pressure altitude.
What are magnetic compass errors?
When the aircraft is accelerated or turned to a new heading, the following two rules apply:
- 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.
- 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.
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.
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
In a METAR, how are clear skies encoded?
- Manual METAR: SKC.
- Automated METAR: CLR.
When a TAF says “TEMPO”, how long are the conditions expected to last?
Generally, less than an hour.
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.
On a METAR, what does VV005 mean?
Vertical visibility, 500 feet.
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.
“High to Low, look out below”
How does temperature affect the altimeter?
When the temperature drops, the altimeter reads higher than actual.
Hot to cold, look out below.
