Weather Information Flashcards
IR.I.B.K1
Sources of weather data (e.g., National Weather Service, Flight Service) for flight planning purposes.
Close to departure time:
Aviationweather.gov, 1800wxbrief, ADSB-IN,
General weather outlook:
Weather channel, internet weather websites, outlook briefing
What is the primary reason for changes in weather?
Uneven heating of the earth
- Variations in solar energy hitting the earth
What is an air mass?
- Bodies of air covering an extensive area
- Fairly uniform properties of temperature and moisture
What does “lapse rate” mean?
- rate in the change of temperature as altitude increases
What is the Dry Adiabatic Lapse Rate?
- the rate of temperature change for dry air
What does Adiabatic mean?
- No heat added or taken away from outside the parcel
What is the Dry Adiabatic Lapse Rate?
- 3 degrees per 1,000ft
What is the standard lapse rate?
- 2 degrees per 1,000ft
What does the Ambient Lapse Rate mean?
- Actual change in temperature as altitude increases
How can the stability of air be determined?
- By the ambient lapse rate
What layer of the atmosphere is most GA flying done?
- The Troposphere
- This is where most weather is located
What is the Tropopause?
- Its the boundary between the Troposphere and the Stratosphere
What is the Tropopause defined by?
- An abrupt change in temperature lapse rate
How high does the Troposphere reach up to?
- 37,000 feet in mid latitudes
What do the Jet Streams consist of?
- Winds of 50kts or greater
What do the Jet Streams do in the winter?
- They move south
- Become stronger
What do the Jet Streams do in the summer?
- The move north
- Become weaker
What are key signs of a stable air mass
- Stratus type clouds
- Poor visibility
- Steady precipitation
- Little to no vertical development of clouds
When do ground based temperature inversions happen?
On calm clear nights. The cloud can be the barrier that creates the inversion.
If there is low level temperature inversion mixed with high relative humidity what can happen?
- Smooth air and poor visibility
- Fog
- Haze
- Low clouds
What is Orographic Lifting?
- This is when an airmass is pushed up over higher terrain
What are the characteristics of unstable air?
- Lots of turbulence
- Good surface visibility
- Towering cumuliform clouds
- Isolated, showery rain
- Possibility of clear icing
What kind of weather conditions create unstable air?
What kind of conditions are associated with unstable air
- Cumuliform clouds
- Turbulence
- Good visibility
What kind of conditions exist with fair weather cumulus clouds?
- Turbulence at and below the cloud level
- Can still indicate convective activity
Key signs of unstable air?
- good visibility
- showery precipitation
- cumuliform type clouds
What is the Coriolis Effect?
it is a force that acts at at right angle to the wind and deflects it to the right until parallel with the isobars
What is surface friction?
Surface friction is usually felt at and below 2000ft AGL and this is what causes winds on the ground
What is always associated with the passage of a front?
- Wind change
In the norther hemisphere what direction does the wind move around a Low Pressure?
- Counter clockwise
In the norther hemisphere what direction does the wind move around a High Pressure?
- Clockwise
How are frontal waves created?
- They form along a slow moving cold or stationary front
- Produces steady precipitation
- Stratiform clouds
- Little to no turbulence
What is radiation fog?
- Warm moist air
- Low flatland
- Clear calm night
- Small temperature/dewpoint spread
What is advection fog?
- Happens in coastal areas
- Moist air moves over cooler ground/ water
What is upslope fog?
- Near mountains and large hills
- Stable air
- Requires wind
What causes fog in industrial areas?
- Condensation nuclei from combustion products
What is the most hazardous aspect of Icing?
- Aerodynamic degradation including loss of lift
How much can ice as thick as medium or coarse sandpaper reduce performance?
- Reduced lift up to 30%
- Increases drag up to 40%
What can small patches of ice or frost on the wings do?
- Possible control difficulties on takeoff
What are two wats that planes deal with icing?
- Anti-icing
- prevents ice accumulation
- De-icing system
- removes accumulated ice
How should de-icing boots be used?
- Inflate the boots early and often
What is residual ice?
- Ice that is left over after boots have been used
- Increases with a decrease in airspeed or temperature
What are the icing values used for reporting icing?
- Trace
- Light
- Moderate
- Severe
What should you do if you fly into icing conditions in Stratiform clouds?
- Change altitude
- warmer than freezing
- Temperature colder than -10c
When would you expect clear ice?
- Temperatures close to freezing
- Large volume of liquid water precipitation
- High speed
When flying through super cooled water droplets what should you look for?
- First sign of ice accumulation
- Probes
- Antennas
What part of the plane collects ice the quickest?
- Leading edge of tailplane
- Collects ice sooner and faster because its thin and narrower than other parts
While using auto pilot while in icing and at cruise what should you do?
- Periodically disengage the autopilot and hand fly that aircraft
Where would ice start to form on climb out after takeoff?
- The underside of the wing
What should you do your best to avoid while in icing conditions?
- Autopilot
= Vertical speed hold
When does frost form?
- Surface temperature below dewpoint
- Dewpoint below freezing
Why is frost dangerous to have on a wing?
- It causes early air flow separation on a wing and decreases lift
- Increases stall speed
What is freezing rain?
- Water that instantly goes from liquid to solid on contact with the aircraft
What does freezing rain indicate as far as temperatures above?
- It means that the air above you is warmer than the air you are currently flying in.
- You can get out of it by climbing to the warmer air
What causes the highest accumulation of structural ice accumulation?
Freezing rain
What do ice pellets indicate?
Freeing rain at higher altitudes
What does wet snow indiacate?
- Temperature is above freezing at current altitude
What do you need in order for a thunderstorm to form?
- Sufficient moisture
- Unstable lapse rate
- Lifting action
What is convection?
- This is when sunshine heats the ground and hot air rises up
- Creates airmass thunderstorms
- Cold fronts can also create the lifting action
- Orographic lifting can create one as well
What are the stages of a thunder storm?
- Cumulus Stage
- updrafts creating the towering clouds
- Mature stage
- Rain begins at surface
- Dissipating stage
- updrafts stop
- downdrafts are most prevalent
Thunderstorms are not reported as such until what happens?
- Thunder is reported or lightning is seen
- reported at Cumulonimbus until this happens
What is the most dangerous cloud to fly through?
- Cumulonimbus clouds
- greatest turbulence associated with these clouds
- AVOID THESE
If you fly into severe turbulence
- Set power to recommended airspeed
- Maintain level flight attitude
- Don’t jerk the plane around, let it fly and make soft corrections
What is an embedded thunderstorm?
- Thunderstorms embedded within massive cloud layers
- Cant see the thunderstorm you could be flying into
What are squall lines
- Develop ahead of a cold front
-Worst kind of storm to fly into or near - Heavy hail
- Destructive winds
What are things to do to avoid thunderstorms?
- DON’T takeoff or land towards a thunderstorm
- Gust front can mess you up
- DON’T attempt to fly through or under a thunderstorm
- DON’T fly under the Anvil of the thunderstorm
- DON’T fly near embedded thunderstorms without weather radar
- DON’T assume ATC will provide this service
- DO stick it out on the ground
- DO avoid thunderstorms by at least 20 miles
- DO ask ATC for radar guidance
What is wind shear?
- An abrupt change in
- strength
- direction
- Shift in direction or speed gradient at any level
Where can wind shear be found?
- Frontal zone
- Temperature inversion
- Jet stream
- Convective activity
What are the stages of a microburst?
- Formation
- Impact
- Dissipation
How strong can a Microburst downdraft velocity get?
- 6,000ft per minute
What are the 2 types of microbursts?
- Wet
- Dry
How long do microbursts tend to last?
- rarely last longer than 15 minutes
Available resources to avoid microbursts?
- PIREPS
- LLWAS
- ATC
What happens upon entering a microburst?
- Increase in performance
- No change in pitch or power
What happens when you are passing through a microburst?
- Severe downdrafts
- Increasing tailwind
What is the definition of a ceiling?
- Lowest layer of clouds or obscuring phenomenon that is either broken or overcastb
what does R31/2700FT on a METAR mean?
Runway visibility is 2700ft
what does +SN mean on a METAR?
Heavy snow
What does RAB35 on a METAR mean?
Rain began 36 minutes after the top of the hour
What does VV008 on a METAR mean?
Vertical Visibility is 800 feet
Used when there is an indefinite ceiling
What does RAE on a METAR mean?
Rain ended
What does SNB on a METAR mean?
Snow began
What are Terminal Aerodrome Forecasts (TAF)?
- Issued 4 times daily
- Usually valid for 24hrs
- TAF’s at bigger airports can last up to 30hrs
- All TAFS include date and times that they are valid for
How are TAF’s reported?
- Wind
- Visibility
- Significant weather
- Cloud cover
you are not given temperatures or altimeter settings
- Cumulonimbus clouds are the only clouds that are forecasted in a TAF
