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