Weather Flashcards
Describe the four different types of fronts
- COLD - Occurs when a mass of cold dense air/stable advances and replaces a body of warm air - OCCLUDED - Occurs when a fast moving cold front catches up to a slow moving warm front (or opposite) Cold occluded/warm occluded fronts - WARM - Occurs when warm air mass contacts and flows over a colder airmass - STATIONARY - Two equal air masses meet the separating front is stationary for days. Both warm/cold weather
Class C airspace- describe/Altitude
- Generally from surface to 4,000 feet MSL - Usually consists of an inner area with 5nm radius and outer circle with 10nm radius that extends 1200-4000 feet MSL - Comms + Mode C
What are the IFR minimums
What are the 5 C’s for a lost aircraft
- Circle
- Confess
- Climb
- Conserve
- Communicate
What is temperature inversion
- When warm air at a higher altitude is above colder air, creating a barrier, trapping pollutants, fog, smoke. Stable air with no turbulence
When significant precipitation is present, how thick can you expect the clouds to be?
At least 4,000 feet thick. The heavier the rain, the thicker the clouds
FAA Advisory circulars containing subject matter specifically related to Airmen are issued under which subject number
What is the equipment required for day time VFR?
ATOMATOFLAMES FAR 91.205
Airspeed indicator
Tachometer
Oil pressure gauge
Manifold Pressure gauge
Altimiter
Temperature gauge
Oil Temperarature gauge
Fuel Gauge
Landing gear position indicator
Anti collision lights
Magnetic Compass
ELT
Safety belts & harness
What are each of the 6 pack instruments
- Airspeed Indicator
- Attitude Indicator
- Altitude
- Turn Coordinator
- Heading Indicator
- Vertical Speed Indicator
What are the 5 types of NOTAM’s
NOTAM D- Taxiway closure, personnel/equipment near or crossing runways, airport lighting (From Weather Message Switching Center (WMSC), located in Atlanta, Georgia.
FDC - Flight Data Center, Advertise temporary flight restrictions caused by natural disasters, or large public events that generate traffic
POINTER - Issued by FSS, paints out other NOTAMS, keywords for TFR must be airspace
SAA - Special Activity Area are active outside scheduled published times
MILITARY- Military activity
What are two ways that fog forms
- Cooling air to the dew point
- Adding Moisture to the air near the ground
What is a center weather advisory?
Center weather advisory (CWA) is an aviation warming for use by aircrews to anticipate and avoid adverse weather conditions in the en route and terminal environments. Not a flight planning product. Valid for two hours
What are the types of PIREPS
- Routine
- Urgent “UA”
- Should be given to the ground facility with which communications are established
With respect to certification privileges, and limitations of airmen, define the terms: Category, Class Type
Category - a broad classification of aircraft: Airplane Rotocraft, Gliderr
Class - Classification of aircraft in a category with similar operating charachteristics: Single Engine Land, Multi Engine Land
Type - Specific Make/Basic Model of aircraft with modifications: DC9, B-737, C-172
What does FAR 61.23 reference? Discuss what they are
Medical Certificates: Requirement/Duration
- Must hold first class for: Airplane PIC privileges etc
- 2nd class for: 2nd PIC of airline
- 3rd class for Private Pilot Cert. Privileges, Etc
- Chart of Med Certs + Requirements
C-172 Electrical System
- 28 Volt DC Electrical System
- 24 Volt Lead Acid Battery
- Electricity is provided by a 60 amp Alternator
- External power receptacle is located on the left side of engine cowl
- Power is distributed by buses and circuit breakers
What is Flight Information Service? Can it be useful in navigation to safely avoid a thunderstorm?
- FIS is a broadcast service provided by an automatic dependent surveillance - Broadcast (ADS-B) service network over the 978 MHz VAT data link
- No they are updated 5-10 mins therefore they are not appropriate for tactical avoidance
What are the equipment requirements for class E airspace?
- No ATC Clearance or radio comms required
- Transponder at or above 10,000 feet
What do you get on a standard Brief?
SAACEDWN
- Synopsis
- Adverse Conditions (Airmet, Sigmet)
- ATC delays
- Current Conditions
- Enroute Forecast
- Destiation Forecast
- Winds Aloft
- Notams
What kind and color hydraulic fluid is used on the C172
What kind/color fuel do we use?
- MIL-H-5604 Red fluid
- 100 Low Lead aviation grade fuel Blue
- 100 octane aviation grade fuel Green
What type of stall warnign system does the 172S have?
Pneumatic stall warning. Inlet on the left leading edge of the wing. Air from top of airfoil gets sucked in Ducted to a horn near the top of the windshield
Precipitation/Weather Type
Surface Analysis Chart
Fog
Precipitation/Weather type
Fog
Surface analysis chart valid 3 hrs
Precipitation/weather type
Surface analysis chart valid 3 hrs
Drizzle
Precipitation/Weather Type
Surface Analysis Chart Valid 3 hrs
Heavy Rain
Precipitation/Weather Types
Surface Analysis valid 3 hrs
First symbol Freezing Rain
Second symbol is Drizzle
What affects density altitude?
Humidity, Temperature, and Altitude affect density altitude
Low Level Significant weather chart
- provides a forecast of aviation hazards
- covers the CONUS
- Depicts: Flying categories, Turbulance, Freezing Levels
- Snap Shot issued 12 hrs and 24 hr prog
- 4x/day
Sky Coverage - Surface analysis Chart valid 3 hrs
Few
Sky Covearage - Surface Analysis Chart valid 3 hrs
Clear
Precipitation/Weather Type
surface Analysis chart valid 3 hrs
Rain Shower
Precipitation/weather type - Surface Analysis chart valid 3 hrs
Rain/Snow shower
Sky Covearage - surface Analysis Chart valid 3 hrs
Sky Coverage Info Missing
Sky Coverage - Surface Analysis Chart Valid 3 hrs
Total sky obscuration (fog)
Precipitation/weather type
- Light Snow
- Moderate Snow
- Heavy Snow
Sky Coverage, Surface Analysis Chart Valid 3 hrs
Breaks in Overcast
Sky Coverage - surface Analyis valid 3 hrs
Scattered
Sky Coverage - Surface Analysis Chart 3 hrs Valid
Broken
Precipitation/Weather Type - Surface Analysis Chart valid 3 hrs
Moderate Rain
Precipitation/Weather Type - Surface Analysis Chart Valid 3 hrs
Light Rain
Sky Coverage - Surface Analysis Chart Valid 3 hrs
Overcast
Wind Barb Examples
Surface Analyis Chart Vali 3 hrs
1) Wind from Northwest @ 10 knots
2) Wind from South @15 knots
3) WInd from Northeast @ 65 knots
Station Model
Surface Analyis Chart, Valid 3 hrs
Precipitation Type - Surface Analyis chart valid 3 hours
Precipitation/Weather Type
Surfae Analyis Chart Valid 3hrs
Contouring/Shading
1) areas with shading indicate IFR conditions
2) Contoured areas without shading indicate MVFR
3) No count ours or shading indicate VFR conditions
Calculate the correct approach speed until short final given the following conditions: Flaps 20 degrees, winds 240 @ 8kts Gusting to 18kts
Add half the gust factor to speed
gust factor: 18-8 = 10
half of 10 = 5
Normal approach speed = 70 + 5 = 75 kts
What are the types of preflight weather briefings?
Standard = Contains 7 elements:
1) Adverse Conditions
2) Synopsis
3) Current Conditions
4) Enroute forecast
5) Destination Forecast
6) winds aloft
7) Notams
Abbreviated = Request an Abbreviated Briefing when you need information to supplement other electronically acquired data (e.g., TIBS or DUATs), update a previous briefing, or when you need only one or two specific items.
Outlook = For future flights in 6 hours. This type of briefing is provided for planning purposes only. You should obtain a Standard Briefing as close to departure as possible in order to obtain the latest current conditions, forecasts, and NOTAMs.
Receiver Autonomous Integrity Monitor RAIM does what?
RAIM (Receiver Autonomous Integrity Monitoring) is also used to establish if the GPS receiver can depend on the position. RAIM only deals with the horizontal position and not the vertical. RAIM works by using 4 satellites to obtain a position. If a fifth satellite is available, RAIM can be calculated by the GPS receiver by substituting the fifth satellite in place of each of the other satellites, replacing one at a time. This provides 5 positions. The closer all the positions are to one another, the more you can depend on the position. This can also be done with additional satellites and can be augmented by the barometric altitude as an input to the algorithm. Sometimes, the geometry of the satellites don’t allow for determining a good position or the number of satellites in view can cause this as well. RAIM is used by the standard GPS and WAAS HPL/VPL is used by a WAAS GPS. If for some reason, the WAAS signal can’t be received, the WAAS GPS defaults to a non WAAS mode of operation and RAIM is used. But for the vast majority of the time, WAAS is available and it is used instead of RAIM.
What is in a Convective Sigmet?
Convective SIGMETs are issued in the conterminous U.S. if these conditions are occurring or expected to occur:
Line of thunderstorms at least 60 miles long with thunderstorms affecting 40% of its length.
Area of thunderstorms covering at least 40% of the area concerned and exhibiting a very strong radar reflectivity or a significant satellite or lightning signature.
Embedded or severe thunderstorms expected to occur for more than 30 minutes.
Special issuance criteria include:
tornado
hail greater than or equal to 3/4 inches in diameter
wind gusts greater than or equal to 50 knots
Any convective SIGMET implies severe or greater turbulence, severe icing, and low level wind shear. A convective SIGMET may be issued for any convective situation which the forecaster feels is hazardous to all categories of aircraft. Bulletins are issued hourly at Hour+55. The text of the bulletin consists of either an observation and a forecast or just a forecast. The forecast is valid for up to 2 hours.
What is a TAF? How many Types?
Terminal Aerodrome Forecasts (TAFs) are concise statements of the expected meteorological conditions within a 5 SM radius from the center of an airport’s runway complex
TAFs can be found on the National Oceanic and Atmospheric Administration’s (NOAA’s) website at http://www.aviationweather.gov/adds/tafs or through use of the java tool here
TAFs can be retrieved in the raw coded format or a translated (decoded) format [Figure 1]
TAFs and Routine Aviation Weather Reports (METARs) are very similar but deviate as wind shear, temperature, icing, and turbulence groups are added to the TAF, when applicable
There are two types of TAF issuances:
Routine forecast issuance (TAF), and;
Amended forecast (TAF AMD)
An amended TAF is issued when the current TAF no longer adequately describes the on-going weather or the forecaster feels the TAF is not representative of the current or expected weather
Corrected (COR) or delayed (RTD) TAFs are identified only in the communications header which precedes the actual forecasts
What are the height of clouts Low, Middle and High?
- Low clouds go from SFC - 6500 = Stratus, Stratocumulus, Nimbostratus
- Middle Clouds go from 6500 AGL - 20,000 Alto Stratus, Alto Cumulus
- High Clouds go higher than 20,000 ft AGL: Cirrostratus, CIrrocumulus, Cirrus
- https://www.cfinotebook.net/notebook/weather-and-atmosphere/clouds
Cumulonimbus are the most dangerous. Classified by the height of their bases
Standard seal level pressure
Standard day at sea level
1013.2
15 degrees Celsius
29.92 altimiter
Define the term windshhear and state the areas in which it is likely to occur
Wind shear is the rate of change of wind velocity (Direction and or speed) per unit distance. Expressed as vertical or horizontal windshear. Can occur at any level in atmosphere but special concerns toward:
- Windshear with low level temperature inversion
- Wind shear in frontal zone/T-storm
- Clear air turbulence @ high levels with Jet stream or strong circulation
What are types of TAF’s?
Routine Amended and Corrected
What is a TRSA?
Terminal Radar Service area
- Delimited area - airspace in which radar and ATC services are made available to pilots flying IFR/VFR for maintaining Separation
- Depicted as Gray shaded area
- Radar Sequencing and Separation Service:
Implemented at certain terminal locations
Service is advertised in the Chart Supplement U.S.
Provides separation between all participating VFR and all IFR aircraft operating within the airspace defined as Terminal Radar Service Area (TRSA)
Pilot participation is urged but not mandatory
If an aircraft does not want this service then state “Negative TRSA Service” on initial contact or as appropriate
VFR aircraft will be separated from VFR/IFR aircraft by one of the following:
500’ vertical separation
Visual separation
Target resolution (a process to ensure that correlated radar targets do not touch) when using broadband radar systems
Participating aircraft must maintain an altitude when assigned, ATC may assign altitudes that do not conform with 91.159 (VFR cruising altitude or flight level)
When altitude restriction no longer applies ATC will advise “Resume Appropriate VFR Altitudes”
Pilots must then return to appropriate 91.159 altitudes as soon as practicable
When not assigned an altitude, the pilot should coordinate with ATC prior to any altitude change
In regards to Surface analysis charts what does this symbol read?
What are the 3 types of aircraft icing you can get?
- Structural: Ice accumulating on aircraft itself
- Induction: on the system, carburator icing
- Instrument: Pitot/Static ports. Pitot gets cold= pitot heat. Static has alternate static source on 172S
Precipitation/Weather Type
Center weather advisory
- Is an aviation warning for us by aircrews to anticipate & avoid adverse weather conditions
- 2 hour period
- 2 hour valid peirod
*
What is a METAR/Speci?
- Aviation routine weather report
- Rapidly changing weather conditions aircraft mishaps or critical information
- Meteorological Terminal Aerodome Report of current weather information released every hour
Sigmets
Potential hazardous to all aircraft.
Issued when necessary and valid for 4 hours
Severe Icing
Severe Turbulance
Dust
What type of weather information will examine to determine if microburst/wind shear affect your flight
- TAF
- METAR
- LLWAS
- Sigmet & Convective Sigmet
- PIREPS
What associates weather with Fronts?
Amount of moisture available, the degree of stability forced upward, speed of the front & Upper wind flow.
Wind and temperature aloft
Forcast for specific locations
issued 4 times a day
winds are not issued for altitudes within 1500ft of a location
Convective Sigmet
Observation & Forecast valid for 2 hours
Severe thunderstorms due to:
- Surface winds greater than 50 kts
- hail 3/4”
- Tornadoes
- Embeded Thunderstorms
- Squal Line
- TS Affecting 40% area 3,000 square miles
Most of the earth weather occurs in what region of the atmosphere?
- Occur in the troposphere which extends from surface to 36,000 ft
- 15 degrees Celsius - 56.5 degrees Celsius
Difference between a stable and unstable atmosphere
- Ability to resist vertical motion
- stable atmosphere makes vertical movement difficult
- unstable atmosphere small vertical air movement tends to become larger: leads to turbulence, extension vertical clouds, severe weather.
Cold Front
Occurs when a mass of cold dense and stable air advances and replaces a body of warmer air.
- Fast moving 30mph
- cumulus clouds
- thunderstorm
- gust
- turbulance
- 25-30 mph
- hail
- tornadoes
*
Temp and dew point are close together within 5degrees F what type of Wx?
visible moisture in the form of clouds, dew or fog
What factors primarily determine the type and vertical extent of clouds?
The stability of the atmosphere
Weather depiction chart
Plot of weather conditions at selected METAR stations
- IFR
- MVFR
- VFR
- LIFR
How can you determine the stability of the atmosphere?
- Stable Lapse Rate of 2degrees Celsius per 1,000 ft
- Unstable more than 2 degrees Celsius per 1000 ft
ex: 3degrees Celsius 1,000 ft
Warm & moist air
7 Types of Turbulance
- Clear Air Turbulence CAT normally occurs outside of clouds at altitudes above 15,000 feet MSL, and its caused by strong wind shears in the jet stream.
- Thermal Turbulence Localized columns of convective current (picture a rising column of warm air) result from surface heating or cold air moving over warmer ground. For every rising current, there is a compensating downward current usually slower in speed, since it covers a broader area, causing turbulence.
- Temperature Inversion Turbulence Even though a temperature inversion produces a stable atmosphere, inversions can cause turbulence at the boundary between the inversion layer and the surrounding atmosphere.
- Mechanical Turbulence When the air near the surface of the Earth flows over obstructions, such as bluffs, hills, mountains, or buildings, the normal horizontal wind flow is disturbed and transformed into a complicated pattern of eddies and other irregular air movements.
- Frontal Turbulence Frontal turbulence is caused by lifting of warm air, a frontal surface leading to instability, or the abrupt wind shift between the warm and cold air masses. The most severe cases of frontal turbulence are generally associated with fast-moving cold fronts.
- Mountain Wave Turbulence As air flows over the tops of mountains, traveling down the leeward side, a standing mountain wave is formed and air currents oscillate between altitudes. Mountain waves and turbulence can extend for hundreds of miles downwind of the mountain range.
- Thunderstorm Turbulence The storm cloud is only the visible portion of a turbulent system in a thunderstorm. But updrafts and downdrafts often extend outside the storm, with severe turbulence possible as much as 15 to 30 miles downwind.
How can a pilot obtain updated weather information?
- FSS
- ATIS
- HIWAS
- ATC
What are PIREPS and where are they usually found?
Pilot Report or PIREP is a report of the actual weather conditions as encountered by an aircraft in flight. Traditionally, these reports are transmitted by radio to an appropriate ground station for dissemination but, when necessary, they can be made by telephone after landing.
FSS
ATC
Aviation Wx.gov
Weather Briefer
Dew Point
The temperature at which air can no longer hold moisture
Once the relative humidity of a mass of air becomes 100%, then if the temperature falls it cannot hold all of the water vapour within it. The excess water vapour will then condense into cloud or fog or, if in contact with objects on or near the ground, will form dew or hoar frost.
When observing successive weather reports (METARs), a reducing gap between the actual temperature and the Dew Point temperature gives an indication of impending low visibility conditions and the posibility of fog.
Why is windshear an operational concern to pilots?
because unexpected changes in wind speed & direction can be potentially hazardous to aircraft operation at low altitudes on approach to and departing from airports
What is ATIS?
Automatic Terminal Information Service:
recording that some airports broadcast in order to reduce frequency congestion. Current weather information, active runway information, NOTAMs, and other useful pieces of information are included in the ATIS. The ATIS is usually updated every hour or when there is a sudden weather change at the airport. ATIS is how pilots get the latest information about an airport over the radio and this is simulated in VATSIM.
What is HIWAS?
What airplane characteristics will be observed in the following windshear situation? Sudden increase in headwind? Sudden Decrease in headwind
- Increase in headwind:
- As a tailwind shears to a constant headwind an increase in airspeed and altitude occurs along with a pitching tendency
- reaction is to pull power and reduce pitch but the situation calls for the exact opposite
- Sudden decrease
- Add power and higher pitch attitude to continue
- Climb to remain on the glideslope
3 Types of Airmets:
- Sierra: IFR & Mountain Obscuration
- Tango: Moderate turbulance or low level wind shear
- Zulu: Moderate Icing
Four types of inflight aviation weather advisories
- Sigmet
- Convective Sigment
- Airmet
- Center Weather advisories
IFR Ceiling and visibility
ceiling 500 to < 1,000 feet AGL and/or visibility 1 to 3 s.m.
Describe the various type of weather obscuring programs now in use
Manual Observation Reports made from airport locations staffed
AWOS: Computer generated voice weather data updated minute to minute
ASOS: minute to minute observation necessary to generate METARS and other aviation weather information
Examples of charts and reports for determining location of thunderstorm:
- Convective Outlook
- Significatn weather chart
- Weather radar observation
- Convective Sigmets
- Pilot Reports
- Supplementary Weather Products
Sample station plotting
Warm Front
The boundary area formed when a warm air mass contacts and flows over a colder air mass (google a picture)
- Slow moving
- Warm moist air
- Low Ceiling
- Poor visibility
- light moderarte precipitation
- Stratiform clouds
- Drizzle
- Rise in temp
*
VFR ceiling and visibility
VFR: Ceiling greater than 3000 feet and visibility greater than 5 miles (includes sky clear).
VFR = >3000′ and >5 miles
MVFR Ceiling and Visibility
Marginal VFR (MVFR): Ceilings 1,000 to 3,000 feet and/or visibility is 3-5 miles inclusive.
MVFR = 1000-3000′ and/or 3-5 miles
Precipitation/Weather type Surface Analysis chart:
Haze
Relative Wind
The direction of airflow with respect to an airfoil. It is parallel and opposite the path of the airfoils movement.
Surface Analyis chart
- Surface Analysis Charts are computer-generated charts with frontal and pressure analysis issued from the Hydro-meteorological Prediction Center (HPC). Locations of High, Low, Trough, ridges, Fronts, Sea Level Pressure
- Issued every 3 hours
Valid Time (VT) of the chart on the lower left corresponds to the time of the observations
Valid time is given in UTC
Information is about 2-3 hours old
Information is all observed data
Occluded Front
occurs when a fast moving cold front catches up with a slow moving warm front. Warm front prevails but immediately followed by a cold front weather
Stationary Front
When the force of two air masses are relatively equal. The boundary or front that separates the remains stationary and influence the local weather for days
What type of weather briefing is available from an FSS?
- Standard Briefing: Anytime planning a fight & you’ve not received previous brieing
- Abbreviated: Info to supplement mass data & update a previous briefing
- Outlook: Prposed time of departure is six or more hours from the time of briefing
- In Flight Briefing: Update a previous flight briefing
Ridge
Elongated area of relatively high atmosphere pressure
Decending air
Dissipation of cloudiness
Good weather
Trough
Elongated area of low atmosphere pressure
rising air
Conductive to cloudiness and precipitation
hence bad weather
Define wind shear and slate the areas in which it is likely to occur
The rate of wind velocity per unit, it occurs
- Low Level temperature inversion
- Frontal zone or thunderstorm
- Clear air turbulance
What is relative Humidity
The actual amount of moisture in the air compared to the total amount of moisture it can hold at that temp
EX. Relative humidity at 65%. Means 65% of the moisture the air can hold at that pressure and altitude
On a Surface analysis chart what do these wind symbols mean?
Sample Station Plottingg (Weather Depiction Chart)
What weather comes with cold front
Cumulus
Unstable
Showery precipitation
Good visibility
When the term “light and variable” is used in reference to a winds aloft forecast, the coded group and windspeed is..?
9900 and less than 5 knots
when the forecast speed is less than 5 knots, coded group is 9900
What are the marginal VFR minimums?
- MVFR = Ceilings 1,000-3,000 feet and or 3-5 am visibility
- Maintain VFR cloud clearance when in class E
- Blue Dot also means minimum
Atmospheric pressure differences, Coriolis force, friction, and temperature differences of the air near the earth cause what atmospheric motions?
Convective currents (Upward and downward motion) and winds (horizontal motion)
What are the types of weather observations?
- Surface, upper air, radar, satelite
Observations gather data from surface and upper altitude to from the basis of all weather forecasts advisories and briefings
What is sublimation?
the changing of ice directly to water vapor bypassing the liquid stage
What are the layers of the atmosphere?
- Thermosphere = 280,000 ft and up
- Mesosphere = 160,000 ft - 280,000 ft
- Stratosphere = 20,001 - 160,000 ft
- Troposphere = sfc - 20,000ft
- Tropopause = Traps moisture and weather
Composition of air?
78% Nitrogen, 21 % Oxygen, 1% Trace gas
Why do Winds generally flow across the isobars at an angle?
Surface friction
Slows the winds and the coriolis effect/pressure gradient force to not be equal since slow winds are less affecte by coriolis
Standard Lapse Rate
Decreases at a rate of 2 Degrees Celsius per 1000 ft of altitude gain
ex
15 degrees = sea level
13 degrees = 1000 ft
11 degrees = 2000 ft
9 degrees = 3000 ft
What are AIRMETS? Describe types
An AIRMET, or Airmen’s Meteorological Information, is a concise description of weather phenomena that are occurring or may occur (forecast) along an air route that may affect aircraft safety. … NOTE: The definition has changed and no longer says “light aircraft”; AIRMETs are intended for all aircraft. Covers 3,000 plus miles, good for 6 hours
- Sierra: Mountain Obscuration IFR, ceilings less than 1,000 feet and/or visibility less than 3 sm over 50%
- Tango: Turbulance, light moderate turbulance, sustained surface winds 30 kts or more
- Zulu: Icing Light - moderate icing/freezing levels
Brush up on METARs and TAFS
Watch YouTube
What are convective sigmets?
Define the following:
Cirrus
Stratus
Cumulus
Cirrus = very high
Stratus: Flat, formed in layers typically low
Cumulus= Stacked on top of one another, puffy, flat base puffy rounded towers
Convective circulation, patterns are cause by? “Associated with sea breezes”
Cool, dense air moving inland over the water
What are the three basic types of clouds?
- Cumulus: fluffy low but build up and bring rain
- Stratus: long, total cloud cover, can bring rain
- Cirrus: high, above 20,000 ft indicate a change in weather is coming
Describe a weather depiction chart and what it includes
- Derived/Generated from METARS
- Includes information on visibility, current weather (rain, snow, fog, etc) sky coverage, and ceiling
- Broadly characterizes IFR, MVFR, VFR
What is SFC based temperature inversion?
What is frontal inversion?
- SFC occur on clear, cool nights when the air close to the ground is cooled but he lowering temp of the ground
- Frontal inversions occur when warm air spreads over a layer of coooler or cooler air is forced under a layer of warm air
The amount of moisture present in the atmosphere depends on the temperature every 20 degrees F plus or minus does what to the moisture?
- Increase in 20 degrees F doubles the amount of moisture air can hold
- Decrease of 20 degrees F cuts the amount of moisture the air can hold in half
During preflight planning, what type of metereológicas information should you be aware of with respect to icing?
- Location of fronts: location type, speed, direction
- Cloud layers: location of clouds base/ceilings, for determining if you can climb above icing layers or decend beneath.
- Freeziing levels: Important to avoid icing conditions
- Air temperature/Pressure: ice tends to be found in low pressure are at temps at or around freezing
What is dry adiabatic lapse rate?
Whats the wet adiabatic lapse rate?
- Dry adiabatic lapse rate is 3degrees C per 1,000 ft
- Wet/moist adiabatic lapse rate varies 1.1-2.8 degreesC per 1,000 feet
What is a trough?
what is a ridge?
- Trough: an elongated area of relatively low atmospheric pressure
- Ridge: an elongated area of high atmospheric pressure
State the general characteristics in regard to the flow of air around high and low pressure systems in the northern hemisphere
Low pressure: inward, upward, counter clock
High pressure: outward, downward, clockwise
At what rate does atmospheric pressure decrease with an increase in altitude?
1” mercury per 1,000 feet
What is a surface chart? Surface analysis
Analyzed charts of surface weather observations. The chart depicts the distribuition of several items including sea level pressure, position of highs, lows, ridges, troughs, the location of fronts, and various boundaries such as dry lines, outflow, sea-breeze, fronts, and convergence lines
Every three hours, high, low pressure, fronts, temp, DP, wind, speed direction, local weather, and obscurations
What are the 4 types of weather advisories?
- Sigmets
- Convective sigmets
- Airmets
- Cennter weather advisory
What do these symbols represent?
What is the forecast of 250 degree, 145 kts encoded as?
270 degree, 199 + kts
On winds aloft?
- 7545 (always 75)
Subtract 100 from speed and add 50 to coded direction
- 7799 (always 77)
winds 200+ kts are indicated as forecast speed of 199 kts
4 types of fog
Radiation (Ground) Fog
Advection Fog
Upslope Fog
Evaporation Fog
Ice Fog
Radiation Fog
Radiation (Ground) Fog:
Radiation, also know as ground fog, forms over low-lying flat surfaces on clear, calm, humid nights [Figure 1]
Typically extends less than 20’ off the ground
As the surface cools by radiation, the adjacent air also is cooled to its dew point
Cloudy nights reflect terrestrial radiation back to the death reducing cooling through a “blanket” effect would prevent formation
Radiation fog actually occurs when the max temperature is reached
Winds 5 to 10 knots result in dense fog while just 5 knots is shallow fog
Fog will dissipate due to winds greater than 10 knots or solar heating
Surface temperature must rise in order for the fog to clear and so thick layers will last longer as it takes longer to heat the ground
Advection Fog
Advection Fog:
Advection fog occurs when a low layer of warm, moist air moves over a cooler surface [Figure 2]
Some wind velocity is required for formation and in fact, the fog becomes thicker and denser as wind speed increases up to about 15 knots
Stronger winds lift moisture into low stratus clouds
Fog can stay over water for weeks, moving over land late in the day and back over the water the next morning
Generally, there are two scenarios which lend to the formation of advection fog:
Cold water rising from the depths to the surface cooling the air above it (i.e., the pacific)
Tropical air moving over cold ground (i.e., the gulf coast)
Solar radiation generally cannot penetrate the thickness to warm the Earth sufficiently and so wind is required to push air from a cold surface to a warm surface, reversing the saturation process
Especially due to the high specific heat of water
Upslope Fog
Upslope Fog:
Forms when moist, stable air is forced up a sloping land mass to a level where the air becomes saturated and condensation occurs [Figure 3]
Requires wind for formation
This type of fog usually forms a good distance from the peak of the hill or mountain and covers a large area
Upslope fog occurs in all mountain ranges in North America
This usually occurs during the winter months, when cold air behind a cold front drifts westward and encounters the eastward facing slopes of the Rocky Mountains
As the cold, moist air rises up the slopes of the mountains, condensation occurs and extensive areas of fog form on the lower slopes of the mountains
Evaporation Fog
Evaporation Fog:
This type of fog forms when sufficient water vapor is added to the air by evaporation and the moist air mixes with cooler, relatively drier air
There are two common types of evaporation fog:
Steam Fog:
Steam or, steaming fog, forms when cold air moves over warm water
When the cool air mixes with the warm moist air over the water, the moist air cools until its humidity reaches 100% and fog forms
This type of fog takes on the appearance of wisps of smoke rising off the surface of the water giving it the nickname “seasmoke” [Figure 4]
Frontal Fog:
This type of fog forms when warm raindrops evaporate into a cooler drier layer of air near the ground
Once enough rain has evaporated into the layer of cool surface, the humidity of this air reaches 100% and fog forms
Ice Fog
Ice Fog:
Occurs in cold weather when the temperature is much below freezing and water vapor sublimates directly into ice crystals [Figure 5]
Conditions for formation are the same as radiation fog except for cold temperature, 25°F and colder
Occurs mostly in arctic regions
Can be blinding to someone flying into the sun
