Weather Info Flashcards
What are examples of sources of weather data (e.g., National WeatherService, Flight Service) for flight planning purposes
ForeFlight, WX Weather Brief, Aviation Weather Center
Aviation Digital Data Service (ADDS)
Automated Surface Observing System (ASOS)
Automated Terminal Information Service (ATIS)
Automated Weather Observing System (AWOS)
Center Weather Advisory (CWA)
Flight Service Station (FSS)
Low Level Wind Shear Alert System (LLWAS)
National Oceanic and Atmospheric Association (NOAA)
National Weather Service (NWS)
Telephone Information Broadcast Service (TIBS)
Transcribed Weather Broadcast (TWEB
What is a METAR? When is it issued and its validity time?
- METeorological Aerodrome Report
- current surface weather conditions
- issued 55 minutes after the hour; updated if significant wx occurs
- valid for 1 hour unless significant wx occurs
What is a TAF?
- Terminal Aerodrome Forecast
- Area of 5SM in radius around issuing airport
- Valid for 24 - 30 hr periods, updated 4 times daily (0000Z, 0600Z, 1200Z, 1800Z)
What kind of weather product will be released in place of a METAR in the event of a significant weather change?
SPECI (Special Issuance)
- issued when wx conditions change drastically between standard reporting periods
What does TEMPO on a TAF mean? What is this an indication of?
temporary change of wx conditions during forecast time
What is an Airmet?
- Airman’s METeorological Information
- Advises of potentially hazardous wx
- Does not include convective activity
- For single engine, light aircraft + VFR pilots
What are the three types of Airmets and the weather associated with each?
- AIRMET Tango: surface winds greater than 30kts and/or mod turbulence
- AIRMET Sierra: mountain obscuration and/or ceilings less than 1000 feet and/or less than 3SM vis over 50% of an area
- AIRMET Zulu: moderate icing and/or freezing level
Define “moderate turbulence.”
- changes in altitude/attitude but positive control at all times
- variations in indicated airspeed
- strains against seatbelts/shoulder straps felt
- dislodged unsecured objects
What is a Sigmet?
- SIGnificant METeorological Information
- in-flight weather bulletin
- non-convective wx advisory for potentially hazardous wx for all aircraft
- unscheduled forecast; valid for 4 hrs unless relating to hurricane (6 hrs)
wx reported: - severe icing
- severe, extreme or clear air turbulence (CAT)
- dust/sandstorms lowering surf/in flight vis below 3SM
- volcanic ash
- hurricanes
Convective Sigmet?
- hazardous convective wx affecting safety of all flights
- issued for severe thunderstorms w/
- 50kts or greater surface winds
- hail @ surface larger than 3/4 inch in diameter
- tornadoes
- embedded thunderstorms
- lines of thunderstorms
- thunderstorms w/ heavy/greater precip affecting 40% or more of a 3000 sq mi or greater area
What is the difference between a Convective Sigmet and a Sigmet?
SIGMET
- non-convective wx
- potentially hazardous for all
- not associated w/ thunderstorms
Convective SIGMET
- associated w/ thunderstorms/convective wx phenomena
Define “severe turbulence”.
- large abrupt changes in altitude/attitude
- large variations in indicated airspeed
- momentarily out of control
What are the different types of turbulence intensity classifications? Define each.
Light: slight erratic changes in alt/attitude
Moderate: change in alt/attitude; positive ctrl @ all times
Severe: large abrupt changes in alt/attitude; momentarily out of ctrl
Extreme: violently tossed about; impossible to ctrl. Possible structural damage
What is the validity period of Airmets? Sigmets? Convective Sigmets?
AIRMET: 6 hrs
SIGMET: 4 hrs
Convective SIGMET: 2 hrs
What is a CWA (Center Weather Advisory) ?
- unscheduled inflight wx advisory for hazardous wx when no other advisory exists
- could also supplement existing advisory
- “nowcast” for conditions developing in next 2 hrs
For cross-country flight planning how would we determine winds for in-flight?
- pre-flight planning = winds aloft chart
- in-flight planning = other sources i.e. GPS
What does 9900 mean on a winds aloft chart?
winds light and variable
What is a PIREP?
Actual in flight wx report conditions given by pilots that are flying
What gasses make up the atmosphere?
- 78% nitrogen
- 21% oxygen
- 1% trace gasses (helium, carbon dioxide, carbon monoxide etc)
What are the layers of the atmosphere?
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
What is considered standard atmospheric temperature and pressure?
Sea level, 15 degrees celcius, 29.92 in hg
Standard lapse rate
-2 degrees Celsuis per 1000’ of elevation change.
What is the lapse rate?
Lapse Rate is the rate at which the temperature and pressure decrease with any gain in altitude.
What are some indications of stable air?
Poor visibility
Stratiform clouds
Continuous precipitation
Absence of turbulence
What are some indications of unstable air?
Good visibility
Cumuliform clouds
Scattered precipitation
Turbulent air
Thunderstorms
What is convection?
Upward & downward movement of air.
What is wind?
Horizontal convection.
What are the three forces affecting wind heading and speed?
Pressure Gradient Force (PGF)
Coriolis Force
Friction
How does pressure travel?
- travels from High to Low
- in northern hemisphere, from left to right (west to east).
What is the coriolis force effect?
Due to the Earth’s rotation, circulating air deflects to the right (N.H.) and to the left (S.H.)
How does air in low pressure systems move? What kind of weather is associated with low pressure zones?
- counter-clockwise inward toward the center and then up
- updrafts, cloudiness, precipitation (thunderstorm conditions)
How does air in a high pressure system move? What kind of weather is associated with high pressure zones?
- clockwise, downward and out from center
- light surface winds, clear skies
What is a Jet Stream?
narrow band of strong winds near tropopause
What is Valley wind?
cold air descending down mountainside
What is Mountain wind?
cold air descending down mountainside
What is Katabatic wind?
- any wind blowing down an incline
- incline influential in carrying that wind
What is Land Breeze?
At night, wind moves from cooled land to warm water
What is Sea Breeze?
during the day, cold air from sea moves to warmer land
What is Wind Shear?
sudden, drastic shift in wind speed, direction or both occurring in vertical or horizontal plane
Do pilots use celsius or fahrenheit in aviation?
Celcius
What is the Standard Lapse Rate?
-2 degrees Celsuis per 1000’ of elevation change.
What is an Inversion?
- layer of atmosphere where air temp increases w/ altitude
- most likely encountered on clear, calm and cool nights
- land cools more rapidly than air causing surface air to cool faster than air aloft
- poor visibility, structural icing at lower altitudes
What is Humidity?
Moisture in the air
What is Relative Humidity?
Saturation level of the air, expressed as a percentage (%)
What is Dew Point?
- temperature where air becomes completely saturated
- 5 degrees or less of temp/dewpoint spread = fog
What is a front?
boundary between 2 different air masses
What is a cold front?
- leading edge of advancing cold air mass
- will replace less dense warm air mass at surface
- faster than warm fronts; up to 40 kts
What is a warm front?
- leading edge of advancing warm air mass
- typically move 50% speed of cold front due to less dense air
What is a stationary front?
- front moving less than 5kts
- cold or warm front cannot overpower the other
What is an occluded front?
- fast cold front catches up with slow moving warm front
- temps of each determines cold/warm front occlusion occurs
- cold front occlusion = air behind occlusion is colder than air in front
- warm front occlusion = air behind occlusion is cold; not as cold as air in front
What is a squall line?
- Narrow band of fully developed thunderstorms
- arranged in a line; high winds, heavy rain
- tend to ass quickly, less prone to produce tornadoes than supercells
What is a dryline?
- low level boundary separating moist from dry air
What is a cloud?
visible moisture
What are the cloud families based on altitude?
- High clouds
- Middle clouds
- Low clouds
High clouds altitudes based on region?
Polar: 10,000 - 25,000ft
Temperate: 16,500 - 40,000ft
Tropical: 20,000 - 60,000ft
Middle clouds altitudes based on region?
Polar: 6,500 - 13,000ft
Temperate: 6,500 - 23,000ft
Tropical: 6,500 - 25,000ft
Low clouds altitudes based on region?
all regions are surface to 6,500ft
Cumulus clouds description
- Big, lumpy, billowy clouds
- Result of convection
- Typically indicate an unstable atmosphere
Stratus Clouds
Uniform, sheet-like clouds resulting from stable air
Cirrus Clouds
ringlets, fibrous clouds, also clouds above 20,000 feet
Castellanus Clouds
clouds with a common base but with separate vertical development, castle-like
Lenticular Clouds
lens shaped, former over mountains in high winds
Nimbus Clouds
Clouds from which rain is falling
Fractus Clouds
Clouds broken into fragments
Alto Clouds
middle-level clouds existing at 5,000 to 20,000 feet
Which clouds would you find in the high altitude family?
- Cirrus clouds
- Cirrocumulus clouds
- Cirrostratus clouds
Which clouds would you find in the mid-altitude family?
- Altocumulus clouds
- Altostratus clouds
Which clouds would you find in the low altitude family?
- Nimbostratus clouds
- Stratus clouds
- Stratocumulus clouds
What is the most dangerous cloud type to pilots?
- Cumulonimbus clouds
- Indicative of turbulence, windshear, thunderstorms, and even microbursts.
What is an Anvil cloud and what does it mean if one forms?
- a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape.
- signifies the thunderstorm in its mature stage
- Avoid flying under it due to hail
What is turbulence?
- ## chaotic changes in pressure and flow velocity.
What are the types of turbulence?
- Convective
- Mechanical (to include Mountain Wave)
What is wind shear?
- Rapid change in wind speed or direction over a relatively short distance
- May be present without visual indications
What is wake turbulence?
- wingtip vortices
- fall down and outward. Avoid it!
What is convective turbulence?
- turbulence is caused by strong updrafts and downdrafts.
- result of uneven heating of the earth’s surface.
- greater the temp difference, the greater the turbulence
What is Mechanical Turbulence?
- Obstructions to wind flow which cause turbulence.
- The higher the windspeed, or the more rough the obstruction, the greater the turbulence.
What are Mountain Waves?
- Develop on the downwind side of mountains.
- As winds rise over the mountains, they may encounter a strong inversion or other stable air
- Causes the winds to be redirected toward the surface.
- The winds usually do not reach the ground; continue in an up-and-down wave-like pattern for hundreds of miles.
What must be present in order for a thunderstorm to form?
- Sufficient water vapor (high dew points)
- An unstable lapse rate
- An initial lifting action
What are the 3 stages of a thunderstorm?
- Cumulus
- Mature
- Dissipating
Describe the cumulus phase
- Characterized by updrafts
- Growth rate up to 3,000 feet per minute
- The cloud grows & water droplets grow too
Describe the mature phase
- Characterized by precipitation, updrafts, and downdrafts
- Up to 2,500 feet per minute
- Extremely powerful downdraft = Microbursts
- Thunderstorm hazards reach their greatest effect
Describe the dissipating phase
- Characterized by downdrafts
- Storm dies rapidly
- No rain/downdrafts = No more thunderstorm
- There are no visual indicators
What are some weather phenomena that come along with a thunderstorm?
- Heavy rain
- Hail. Hail may fall many miles away from the storm.
- Lightning
- Violent turbulence
- Wind shear
- Microbursts
- Tornadoes
- Pressure falls rapidly near the storm
What should you do if you accidentally end up in a thunderstorm?
- Plan the quickest course out of the storm
- Disengage autopilot
- Maintain Attitude (Not Altitude)
- Scan instruments
- Adjust power
What is a Microburst?
- extremely powerful downdraft
- may occur anywhere near thunderstorms, precipitation, or where virga occurs
- lifespan of 10-20 minutes
- 1-3 miles in diameter
- downdrafts rate of 6,000 fpm
What temperature range is icing likely to occur?
- generally between 0°C and -20°C.
- warmer the air temp, more likely the supercooled droplet will hit the leading edge of an aircraft
What are the three areas where icing can occur?
- Induction Icing
- Instrument Icing
- Structural Icing
Describe induction icing
- Ice accumulation blocks air from reaching the engine
- Results of impact/intake icing collecting and blocking the air filter/carburetor icing as the air pressure (and temperature) in the venturi drop.
Describe instrument icing
Icing of the pitot tube and/or static source
Causes erroneous reading of:
- Airspeed Indicator (ASI)
- Altimeter
- Vertical Speed Indicator (VSI)
Most aircraft have pitot heat/static source heat.
- Using the alternate static source can cause erroneous readings/temporary change in these instrument readings.
Describe structural icing
Occurs when:
Flying in visible Moisture
- point where moisture strikes the aircraft is less than or equal to zero degrees celsius
- OAT is between 0 and -20 degrees Celsius
- Supercooled water droplets are present. These liquid droplets are below zero degrees Celsius
- May increase the rate of structural icing
- Freeze upon impact
- Commonly encountered in zones of temperature inversion and where moist air is blown upslope
What are the three types of Structural Icing?
Clear, rime and mixed
What is clear icing
- formed by water droplets spreading and freezing slowly
- smooth sheet of hard, tough to remove ice
- most dangerous icing; difficult to see
- forms near top and bottom of wing near leading edge; disrupts airflow
What is rime icing
- formed by smaller droplets freezing rapidly
- white opaque appearance
- rough surface; greatly reduce aerodynamic efficiency
- vertical avoidance is recommended
- weight is negligible
What is mixed icing
- combo of clear and rime icing
- forms when drops vary in size or when liquid and snow/ice particles are both present
- build rough heavy accumulation
when should ground icing be cleared?
- prior to taxi and takeoff
- taxiing through puddles may produce icing of wheel wells, brakes etc.
What is fog?
- visible aerosol consisting of tiny water droplets/ice crystals suspended in the air at or near the Earth’s surface.
- considered a type of low-lying cloud
- heavily influenced by nearby bodies of water, topography, and wind conditions.
- It is the most common cause of surface visibility less than 3 statute miles and may drop conditions from Visual Flight Rules to less than 1 Statute Mile visibility in under a minute
When is fog primarily hazardous?
takeoff, landing, and while maintaining visual reference to the ground
What are the different types of fog?
- Precipitation fog
- Advection fog
- Ice fog
- Radiation fog
- Upslope fog
- Steam fog
Precipitation fog description
- Forms as warmer precipitation falls through colder air, saturating the air as it evaporates
- Expected where a temperature inversion and precipitation coexist
Advection fog description
- Forms as moist air moves over colder ground or water
- Deepens with winds up to 15 knots
- The winds stir the air causing air to cool to dew point faster
- Above 15 knots and the fog is lifted
- Typically encountered in coastal areas or deep in continental areas
Ice fog description
- Fog composed of ice crystals
- Found on in extremely cold areas (typically below -40 degrees celsius)
Radiation fog description
- Terrestrial radiation from the cooling ground cools the air above it
- The temperature/dew point spread decreases
- This results in radiation fog; deepens with winds up to 5 knots
- Usually disappears rapidly after sunrise
Upslope fog description
- Forms as moist, stable air is pushed up sloping terrain
- Cools adiabatically to the dew point
- Once upslope winds dissipate, the fog does too
Steam fog description
- Forms when cold air moves over warm water
- Moisture from the water surface evaporates, saturating the air
- Commonly observed over lakes and streams on cold mornings and over the ocean during the winter
What is mist?
- intermediate point between haze and fog
- consists of minute water droplets suspended in the atmosphere.
What is frost? When does it occur?
- Formation of thin ice crystals.
- Occurs on solid objects which are below freezing (0° C)
- Often encountered near the surface in clear, calm, and stable air.
How can frost affect our performance? What can we do about it?
- Causes airflow over the wing to slow and can increase the stall speed by 5-10%.
- It can also prevent an aircraft from becoming airborne at normal takeoff speed.
- Imperative all frost be removed before flight
- Usually done with de-icing spray
- Can also be prevented if the aircraft is hangared
What are examples of obstructions to vision?
Listed in the Manual of Surface Observations(WBAN), Circular N; encoded as a part of an aviation weather observation.
- fog
- ground fog
- blowing snow
- blowing sand
- blowing dust
- ice fog
-haze, smoke, dust and blowing spray\
What is haze?
- small dry particles suspended in stable air
- usually has a definitive top with good visibility above the layer
- downward visibility (air-to-ground) is greatly reduced
What is smoke?
- formed from fires or industrial areas due to the combustion process.
- the particles are at their most concentrated at night or early morning
- visibility will generally improve throughout the day.
What is Automatic Dependent Surveillance - Broadcast (ADS-B) and how does it work?
- precise tracking via satellite
- Allows equipped aircraft and ground vehicles to broadcast their identification, position, altitude and velocity to other equipped vehicles and ATC.
FAR 91.225 requires ADS-B to operate
- Anywhere above 10,000’ MSL
- Below 10,000’ MSL within the lateral limits of Class C & B Airspace, from the surface to 10,000’ MSL
- Within 30 nautical miles of airports listed in FAR Part 91,Appendix D, Part 1
ADS-B Out periodically broadcasts
- position
- direction
- speed
ADS-B In depicts:
- position and velocity of other traffic using TIS-B within one’s cockpit
- weather via FIS-B
- terrain hazards
- Other info (i.e. Temporary Flight Restrictions)
What is TIS-B and how does it work?
- Traffic Information Service Broadcast
- Available to aircraft equipped with ADS-B In and a cockpit display of traffic
- Depicts other aircraft in flight
- Aids in collision avoidance
- Should never be used as a primary means of collision avoidance
- Pilots may receive a temporary target of themselves, known as a ghost
What is FIS-B and how does it work?
- Enhances decision-making/safety through awareness of weather/airspace constraints
- Available to ADS-B equipped aircraft via the Universal Access Transceiver (UAT) Network (978 MHz)
- Augments communication with ATC facilities
- May provide pilots with graphical and textual weather products
- viewed as advisory only
- Pilots planning to use non-FAA FIS-B should determine whether or not the information provided has been directly sourced from the NWS
What are go/no-go decisions?
- most important decision a pilot routinely makes
- decision is easy to make if the pilot is fit for flying, weather is good, the aircraft is airworthy, and the “mission” is well within the pilot’s comfort zone.
What are the factors involved in making a go/no-go decision?
PAVE
- Pilot - Are you as the PIC safe to fly?
- Aircraft - Is the aircraft legal and safe to fly?
- enVironment - Will weather conditions permit the flight to happen safely?
- External Pressures - Is there any external or internal pressure influencing your decision?
What is a diversion, and when would a diversion be necessary?
- Diversion – A landing at an airport, other than the intended destination airport, for reasons beyond the control of the pilot
- A diversion may occur for any reason (weather, medical reasons, change of plans, mechanical, etc.)
- A diversion differs from an emergency landing
What are the most common causes for diversions?
- Presence of significant weather
- Medical emergency
- Conducting a successful diversion
- The easiest way to divert is visually, using pilotage and dead reckoning
○ Pilotage – Visual navigation from checkpoint to checkpoint using outside references
○ Dead reckoning – Navigation via a predetermined course based on the expected winds and aircraft velocity
○ Calculating the top of descent
■ The “3 to 1 Rule” - You will travel 3 nautical miles per 1,000’ you descend as long as the rate of descent equals a rate of descent of 500 FPM
What are personal minimums? Why are they important to have?
- An individual’s set of procedures and guidelines for deciding under what conditions to operate or continue operating an aircraft
– Standard against which we judge conditions to make go/no-go or continue/divert decision
Should you take off for a cross country flight from an airport where ceilings are 1000 feet AGL and there is an icing PIREP 5 nautical miles east of the airport at 1500 AGL?
No, you cannot maintain VFR cloud clearances with 1000 foot ceilings. ifyou filed IFR you would almost certainly accumulate icing in some form.
What is the most prominent limitation of our onboard weather?
- info is considered “near real time”
- often is delayed from when the data is obtained to when it is received in the aircraft
- delays can range from one minute to thirty minutes
- important to remember that the information received through the EFD is weather “that was” and not weather “that is.”
What are the limitations of weather reports and forecasts?
Not one chart is perfect, therefore you should use a combination of weather imagery to get a complete picture of the weather patterns.
What is a limitation of a MOS weather report?
- A MOS (Model Output Statistics) weather report uses historical data to compute what future weather conditions will be
- Unlike a TAF which uses meteorologists to forecast weather conditions
What is a limitation to a TAF?
They are only issued every 6 hours and are only valid for a 5 statue mile radius around a given airport.
What type of weather product is a METAR and how can that be a limitation?
A METAR is an observation, which in and of itself can be a limitation due to outdated weather because of the time it takes to update a METAR (hourly)
What are the limitations of inflight weather resources?
- Range of up to 300 miles, which means pilots are not able to see the weather beyond that scope.
- Center Weather Advisories (CWA) give weather information as it occurs; not available for planning purposes. - – - limitation of FSS is that they can communicate with only one aircraft at a time; can cause delays in obtaining information
NEXRAD shortcomings
- difficulty distinguishing between heavy rain and hail
- radar uses lower elevation angles which causes only weather at lower altitudes to be detected.
- Higher altitudes closer to the radar site may not show precipitation, even when it exists
- NEXRAD information is not instantaneous and will be outdated up to 20 minutes.
