Weather Flashcards
What are the primary means of obtaining a weather briefing?
1800-WX-Brief
Flight Service Station
Name some sources of obtaining weather information
1800-WX-Brief
Aviationweather.com
Foreflight
National Weather service
What are the standard temperature and pressure values for sea level?
15°C
29.92
1013.2 hectopascal
How does air flow in the northern hemisphere for a high-pressure
system?
Downwards, Clockwise and out
Stable air
How does air flow in the northern hemisphere for a low-pressure system?
Counter clockwise, in, and upward
Unstable air
What kind of weather can you expect to come from a high-pressure system?
A high-pressure system typically brings clear skies, calm winds, and fair weather due to the descending air mass which inhibits cloud formation and results in dry conditions; essentially, settled weather with little to no precipitation
dry cool air declines and warms up
anti-cyclone
What kind of weather can you expect
to come from a low-pressure system?
A low-pressure system typically brings cloudy, unsettled weather with a high chance of precipitation, including rain, snow, or storms, often accompanied by wind as air moves towards the low pressure area, causing the moist warm air to rise to condense and form clouds; essentially, expect potentially stormy conditions with varying levels of precipitation depending on the system’s strength and moisture content.
low moist warm air rises and cools down
cyclone
Describe the four types of fronts
Cold Front
Warm Front
Occluded Front
Stationary Front
what would the weather look like in a cold front
A cold front typically brings a narrow band of precipitation, often including thunderstorms, heavy rain, and sometimes hail or snow squalls, as the colder air mass pushes up the warmer air, causing moisture to condense and fall as precipitation; after the front passes, the weather usually clears with cooler temperatures and drier conditions.
what would the weather look like in a warm front?
A warm front typically brings a gradual increase in temperature, increased humidity, and steady, light to moderate precipitation, often appearing as widespread cloud cover with rain or drizzle, as the warm air mass rises over a cooler air mass, causing moisture to condense into clouds and precipitation; you might see high cirrus clouds approaching before the front arrives, followed by thicker altostratus clouds and eventually rain.
what would the weather look like in a cold front?
Cold fronts are the opposite of warm fronts, with colder air advancing close to the surface.
This forces the air up and away as the front moves.
Cold fronts generally move at 25-30 miles per hour, but cold fronts have been recorded at up to 60 miles per hour in extreme cases. This quick movement of warmer air upwards causes the creation of clouds as moisture condenses.
Depending on the stability of the warmer air mass, the cloud type may change.
Typically, these clouds are either towering cumulus or cirriform. However, cumulonimbus clouds may develop.
Cumulonimbus clouds can result in lightning, thunder, hail, and even tornadoes in severe cases.
what would the weather look like in a warm front?
Warm fronts occur when a warm air mass advances and replaces a colder body of air, covering the colder air from the top and forcing the cold air out below.
This type of front moves slowly, typically at about 10-25 miles per hour.
Generally, as this air is forced upwards by the frontal change, stratiform and cirriform clouds and fog can be expected.
In the summer months, this lifting action can trigger cumulonimbus clouds.
Precipitation is light to moderate, accompanied by poor visibility.
During the passage of a warm front, stratiform clouds are visible, and drizzle may fall.
The visibility is generally poor but improves with variable winds. The visibility eventually improves after the passage of a warm front, but hazy conditions may exist for a short period after passage.
There is generally a slight rise in barometric pressure, followed by a decrease in barometric pressure.
what would the weather look like in a Stationary Front?
Stationary fronts occur when the forces of two air masses are relatively equal, causing the front not to move.
A stationary front can sit over an area for a prolonged amount of time.
Weather conditions associated with a stationary front vary widely, but they’re generally a mix of cold and warm front conditions.
what would the weather look like in a Occluded Front?
Occluded fronts occur when a faster-moving cold front catches up to a slower-moving warm front.
As the occluded front approaches, we can expect warm front weather immediately followed by cold front weather.
Occluded fronts have two variants: a cold front occlusion and a warm front occlusion.
The type depends on the temperature of the air mass ahead of both warm and cold fronts, compared to the cold front that is catching up to the warm front.
Let’s look at both variants in further detail.
What is dew point?
the temperature at which air must be cooled to become saturated with water vapor and produce condensation
What can you
expect if the temperature and dew point are close together?
When the temperature and dew point are close together (within 5°), you can expect high humidity because the air is near saturation with moisture, which means there is a high likelihood of fog, clouds, or precipitation forming, especially if the temperatures continue to cool further.
Stable air brings what type of clouds, visibility and precipitation?
Stable air brings layered clouds, such as stratus clouds, and can cause steady precipitation. Stable air can also cause low visibility due to particles like dust, haze, and smoke.
Unstable air brings what type of clouds, visibility and precipitation?
Unstable air is associated with cumulus clouds, showery precipitation, and good visibility.
What are isobars and what does it mean when they are close together?
Isobars are lines on a weather map that connect areas of equal atmospheric pressure, and when they are close together, it indicates a steep pressure gradient, meaning strong winds are likely to occur in that region; essentially, the closer the isobars, the stronger the wind speed.
What is the difference between a trough and a ridge?
A “trough” refers to an elongated area of relatively low atmospheric pressure, while a “ridge” is an elongated area of relatively high atmospheric pressure
What do you need for a
thunderstorm to form?
Moisture
Water vapor is necessary to create clouds and precipitation. Moisture usually comes from oceans.
Instability
The air must be unstable, meaning it’s warmer than the air around it and rises on its own. This can happen when warm, moist air is near the ground and cold, dry air is above.
Lift
A lifting mechanism is needed to provide the “nudge” that starts the air moving. This can be caused by hills or mountains, or when warm/cold or wet/dry air bump together.
Name the thunderstorm Stages
Developing Stage:
This is when the cumulus cloud begins to form and rise due to updrafts of warm air.
Mature Stage:
The storm reaches its full intensity with strong updrafts and downdrafts, producing heavy rain, lightning, thunder, and potentially hail.
Dissipating Stage:
The storm weakens as the downdrafts become dominant, cutting off the updraft and causing the cloud to dissipate.
Name the types of thunderstorms
Single-cell
Small, weak storms that usually last less than an hour. They are often caused by heating on a summer afternoon.
Multi-cell
Made up of many convection cells that move together. These storms can produce a lot of rain and are more likely to cause flooding.
Squall line
A line of multi-cell storms that forms along a cold or warm front. Squall lines can be up to 600 miles long and are often preceded by strong gusts of wind.
Supercell
Large, organized storms that can produce severe weather, including:
High winds
Large hail
Strong tornadoes
Heavy rain
Downbursts that can produce outflow winds of over 100 mph
Explain the different types of fog?
S - Steam Fog
Formation: Occurs when cold air moves over warmer water. The water vapor rises, cools, and condenses.
Example: Seen over lakes or oceans in colder months.
Appearance: Wispy or patchy fog above the water, sometimes called sea smoke.
U - Upslope Fog
Formation: Created when moist air is forced up a slope (e.g., mountains or hills). As the air rises, it cools adiabatically and condenses.
Example: Found along the windward side of mountains.
Appearance: Dense fog covering elevated terrains.
G - Ground Fog
Formation: A type of radiation fog forming near the ground, usually less than 20 feet deep.
Example: Common in valleys during calm, clear nights.
Appearance: Thin, localized fog close to the surface.
A - Advection Fog
Formation: Develops when warm, moist air moves over a cooler surface, causing the air to cool to its dew point.
Example: Seen near coastal areas when warm ocean air drifts over colder land.
Appearance: Thick, widespread fog.
R - Radiation Fog
Formation: Forms on calm, clear nights when the ground cools rapidly, cooling the air above it to the dew point.
Example: Common in the early morning in low-lying areas.
Appearance: Shallow and dissipates with the sun’s heat.
P - Precipitation Fog
Formation: Occurs when rain falls through cooler air, and the rain evaporates into the air, saturating it to the dew point.
Example: Found ahead of warm fronts during rain.
Appearance: Dense fog accompanying rainy conditions.
I - Ice Fog
Formation: Develops in extremely cold temperatures (below -25°F), where water vapor sublimates directly into ice crystals.
Example: Common in Arctic or Antarctic regions.
Appearance: Sparkling ice crystals in very cold environments.
Define wind shear?
Wind shear is a change in wind speed and/or direction over a short distance. It can occur either horizontally or vertically and is most often associated with strong temperature inversions or density gradients. Wind shear can occur at high or low altitude.
How did you determine the weather for today’s flight?
Primary Sources:
I accessed weather information using [ForeFlight/1800WXBRIEF/Aviationweather.gov].
I reviewed the current METARs and TAFs for the departure airport, enroute, and destination airports, checking wind, visibility, and cloud ceilings.
Big Picture:
I analyzed the Surface Analysis Chart for general weather patterns, such as high and low-pressure systems, and any fronts that might affect the route.
I also reviewed Prog Charts to see the forecasted weather trends along the route.
Hazardous Weather:
I checked for AIRMETs, SIGMETs, or Convective SIGMETs for turbulence, icing, or thunderstorms.
I noted any PIREPs for in-flight conditions reported by other pilots.
Winds and Temperature Aloft:
I reviewed the Winds and Temperature Aloft Forecast to plan my altitude and determine fuel efficiency.
NOTAMs:
I checked for any active NOTAMs that could affect the flight, including TFRs or runway closures.
In-flight Updates:
If necessary, I plan to use Flight Service (122.2) or onboard weather tools to stay updated on changing conditions.”
How can you receive updated weather inflight?
Flight Service Station
ATC
What is a METAR? Issuance, valid times, area of coverage?
“Meteorological Aerodrome Report” is a standardized weather observation taken at an airport, providing pilots with current information about conditions like wind, visibility, cloud cover, precipitation, temperature, and altimeter setting
issued every hour, is valid for one hour
5 SM of the station
What is the difference between statue and nautical miles?
Statute mile: Used for land distances, considered the standard “mile” most people think of.
Nautical mile: Used for maritime navigation, calculated based on the Earth’s curvature.
If there is a $ at the end of a METAR, what does that signify?
the weather observing equipment needs maintenance
What is a TAF? Issuance, valid times, area of coverage?
a weather forecast specifically for an airport and its immediate surrounding 5nm, providing information about expected wind, visibility, cloud cover, and significant weather phenomena within a 24-hour timeframe, usually issued every 6 hours. 4 times a day
Decode your local METAR
Decode your local TAF
What is the definition of a ceiling?
Ceiling means the height above the earth’s surface of the lowest layer of clouds or obscuring phenomena that is reported as “broken”, “overcast”, or “obscuration”, and not classified as “thin” or “partial”
Do TAFs and METARs report in MSL or AGL?
TAFs and METARs report weather conditions in AGL (Above Ground Level)
What is an Area Forecast? Issuance, valid times, what information is provided?
a weather forecast for pilots, covering a large geographical area spanning several states, providing details about expected cloud conditions, general weather patterns, and visual meteorological conditions (VMC), typically issued three times a day with a validity period of 18 hours
What are PIREPs and what are the types?
“Pilot Report,” is a report from a pilot detailing actual weather conditions they are encountering in flight
used to alert other pilots about potentially hazardous weather and help them plan their flight accordingly;
the two main types of PIREPs are “routine” (UA) and “urgent” (UUA), with urgent reports signifying severe weather like tornadoes, severe turbulence, or severe icing
Where can PIREPs be found?
AviationWeather.gov
ATC
Flight Service Stations
Weather.gov
What information is on a Pirep?
3−letter station identifier Nearest weather reporting location to the reported phenomenon
Report type
Routine UA
Urgent PIREP UUA
Location /OV
In relation to a VOR
Time/TM ZULU
Altitude/FL Essential for turbulence and icing reports
Aircraft Type/TP
Essential for turbulence and icing reports
Sky cover/SK
Cloud height and coverage (sky clear, few, scattered, broken, or overcast)
Weather/WX
Flight visibility, precipitation, restrictions to visibility, etc
Temperature/TA
Degrees Celsius
Wind/WV
Direction in ° magnetic north and speed in knots
Turbulence/TB
As per AIP definitions
Icing/IC
As per AIP definitions
Remarks/RM
KCMH UA /OV APE 230010/TM 1516/FL085/TP BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT
KCMH - Closest weather reporting airport (Columbus Ohio)
UA - Routine PIREP
/OV APE 230010 - location one zero miles southwest of Appleton VOR
/TM 1516 - time 1516 UTC
/FL085 - altitude eight thousand five hundred
/TP BE20 - aircraft type Beech 200 Super King Air
/SK BKN065 - base of the broken cloud layer is six thousand five hundred
/WX FV03SM HZ FU - flight visibility 3 miles with haze and smoke
/TA 20 - air temperature 20 degrees Celsius
/TB LGT - light turbulence
UACN10 CYXU 271338 YZ UA /OV CYYZ 180055 /TM 1338 /FLDURD /TP A319 /TB MDT 200-240 /IC MDT MXD 040-050
What are In-flight Aviation Weather Advisories?
Inflight Aviation Weather Advisories are forecasts to advise en route aircraft of development of potentially hazardous weather
AIRMET? Issuance, valid times, types?
Area Meteorological Information issued every six hours, typically valid for six hours, and alerts pilots to widespread weather conditions like moderate turbulence, low-level wind shear, moderate icing, or significant IFR conditions across a large area, with three primary types: Sierra (IFR conditions), Tango (Turbulence), and Zulu (Icing).
SIGMET? Issuance, valid times, why are they issued?
“Significant Meteorological Information,” issued to pilots when potentially hazardous non-convective weather conditions exist, like severe icing, extreme turbulence, widespread dust storms, or volcanic ash, and is typically valid for up to four hours, with extensions possible for situations like hurricanes or volcanic ash clouds where the duration might be extended to six hours; it is issued as needed when these conditions are detected or expected to occur.
what is Winds and temperatures aloft
forecast?
a weather prediction that provides information about the wind direction, speed, and temperature at various altitudes in the atmosphere
issued twice a day
When is Winds and temperature aloft issued?
0000Z and 1200Z
it is issued twice a day
four times daily for specified locations in the CONUS, the Hawaiian Islands, Alaska and coastal waters, and the western Pacific Ocean
Why is the winds and temperature aloft not present at lower altitudes
(i.e. 3000, 6000) at some stations?
the atmospheric conditions near the ground are heavily influenced by local factors like terrain, surface heating, and friction, causing significant variability in wind direction and speed, making it less reliable to forecast at lower levels compared to higher altitudes where the air is more stable and influenced by larger-scale weather patterns
You see 9900 on the winds and temperature aloft, what does that mean?
the wind is “light and variable,” meaning there is a very low wind speed with no defined direction at that altitude
What does 731960 mean on a winds and temperature aloft forecast?
subtract 50 from the first two digits (73) to get the wind direction (230 degrees), add 100 to the next two digits (19) for the wind speed (119 knots), and the final two digits represent the temperature (-60 degrees Celsius)
230 wind direction
119 wind speed
-60°C
What happens to the winds aloft formatting at an altitude of 24,000?
the winds aloft formatting changes so that the temperature is always considered negative, meaning the minus sign is omitted from the temperature reading because temperatures at that altitude are always below zero degrees Celsius
What is a Graphical Forecast for Aviation?
What information does it
provide?
A Graphical Forecast for Aviation (GFA) is a visual representation of weather conditions that could impact flights, displayed on a map and providing information like
cloud cover, precipitation, turbulence, icing potential, wind speed and direction, allowing pilots to easily see potential weather hazards along their flight path and make informed decisions about their route and altitude
What is a Surface Analysis Chart? Issued? Valid? What information does it provide?
A Surface Analysis Chart is a weather map that depicts current weather conditions at the Earth’s surface, including information like pressure systems, fronts, temperature, wind direction and speed, and sky cover, allowing users to identify areas of potential weather activity; it’s typically issued every few hours and is only valid for a short period due to rapidly changing weather patterns.
What is a Weather Depiction Chart? Issued? Valid? What information does it provide?
a graphical representation of current weather conditions at various locations, typically used in aviation, which provides a quick overview of areas with Visual Flight Rules (VFR), Marginal VFR (MVFR), and Instrument Flight Rules (IFR) conditions by displaying information like visibility, ceiling, sky cover, and weather phenomena based on METAR observations at specific weather stations; it’s usually issued every few hours and is valid at the time of observation.
What is the Significant Weather Prognostic Chart? Issued? What information does it provide?
forecast map used primarily by pilots, displaying anticipated weather conditions like turbulence, freezing levels, precipitation areas, fronts, and pressure systems at various altitudes over a specific time period, allowing them to plan flight routes to avoid potential hazards
What are the three types of aircraft icing?
Clear ice
is a heavy coating of glassy ice which forms when flying in areas with high concentration of large supercooled water droplets, such as cumuliform clouds and freezing rain. Droplet freezes on impact forming solid sheet of clear ice
What are the three types of aircraft icing?
Rime ice
is an opaque, or milky white, deposit of ice that forms when the airplane is flying through filmy/stratiform clouds. aircraft skin must be at a temperature below 0°C. The drop will then freeze completely and quickly without spreading from the point of impact
The deposit has no great weight, but its danger lies in the aerodynamic alteration
What are the three types of aircraft icing?
Mixed icing
has the properties of both clear and rime icing. Large and small supercooled droplets coexist. Appearance is whitish, irregular and rough. Favorable conditions include liquid and frozen particles found in the colder portion of the cumuliform cloud and wet snow flakes. The formation process for mixing icing includes that of clear and rime icing. Mixed ice can accumulate rapidly and is difficult to remove.
What conditions are necessary for structural icing?
visible moisture in the air, like clouds or rain, and a temperature at the point where the moisture hits the aircraft that is at or below freezing (0°C or colder)
Can you take off with frost?
No, according to FAA regulations, it is prohibited to take off with frost, ice, or snow adhering to any critical surfaces of the aircraft, including the wings, propellers, or control surfaces, meaning you must remove all frost before takeoff.
Reduced lift, Increased drag, Control issues
Which weather hazards might include wind shear?
Thunderstorms: Wind shear is a key factor in the formation of supercell thunderstorms, which can produce tornadoes.
Frontal activity: Wind shear is often associated with fronts that have steep wind gradients.
Temperature inversions: Wind shear can occur when cooler air is forced closer to the surface.
Surface obstructions: Wind shear can be caused by buildings, mountains, wind turbines, and sailboats.
Microbursts: Wind shear is commonly observed near microbursts, which are violent outflows of air that occur in association with large storms.
how would the plane perform in a low pressure system
In a low-pressure system, aircraft performance is generally reduced because the air is less dense. Here’s how it impacts performance:
Reduced Engine Power: The engine produces less power due to lower oxygen levels in the thinner air.
Decreased Propeller Efficiency: The propeller generates less thrust as it moves through less dense air.
Longer Takeoff Roll: The aircraft requires more runway to achieve the necessary lift-off speed.
Reduced Rate of Climb: Thinner air results in less lift and thrust, slowing climb performance.
Impaired Aerodynamics: Wings generate less lift, and control surfaces may feel less responsive.
Low-pressure systems are often associated with warmer temperatures and moist air, which can further decrease performance due to higher density altitude. Additionally, the unstable weather conditions (e.g., clouds, precipitation, and turbulence) common in low-pressure systems may also create operational challenges.
how would the plane perform in a high pressure system?
In a high-pressure system, the plane typically performs better because the air is denser. Here’s how it affects performance:
Improved Engine Power: Denser air provides more oxygen for combustion, allowing the engine to produce more power.
Increased Propeller Efficiency: The propeller can generate more thrust in denser air.
Shorter Takeoff Roll: The aircraft reaches lift-off speed more quickly, requiring less runway.
Higher Rate of Climb: The increased lift and thrust improve the climb performance.
Better Aerodynamic Efficiency: Wings generate more lift in dense air, improving overall stability and control.
High-pressure systems are often associated with cooler temperatures and clear skies, which further enhance performance due to lower density altitude. This makes operations in a high-pressure system more favorable.
what is the performance of a plane in a high density altitude?
In high-density altitude conditions, aircraft performance is significantly reduced because the air is less dense. Here’s how it affects performance:
Reduced Engine Power: Engines produce less power in thinner air because there is less oxygen available for combustion.
Decreased Propeller Efficiency: Propellers generate less thrust as they move through less dense air.
Longer Takeoff Roll: The aircraft requires more runway to achieve the necessary lift-off speed.
Reduced Rate of Climb: Climbing is slower due to decreased thrust and lift.
Impaired Aerodynamic
Performance: Wings generate less lift because the air molecules are farther apart.
High-density altitude is commonly caused by high elevation, high temperature, and high humidity, and pilots must account for it in performance calculations to ensure a safe flight.
what is the performance of a plane in a low density altitude?
In low-density altitude conditions, aircraft performance is optimal because the air is denser. Here’s how it improves performance:
Increased Engine Power: The engine produces more power because there is more oxygen available for combustion.
Enhanced Propeller Efficiency: The propeller generates more thrust as it moves through denser air.
Shorter Takeoff Roll: The aircraft reaches lift-off speed more quickly, requiring less runway.
Higher Rate of Climb: Denser air allows for increased lift and thrust, improving climb performance.
Better Aerodynamics: Wings generate more lift, and control surfaces are more effective.
Low-density altitude is typically found in low elevations, cooler temperatures, and dry air, making it ideal for flight operations. Pilots can expect smoother performance and improved safety margins in these conditions.
Cold Occluded Front
Description: The cold air behind the cold front is colder than the cool air ahead of the warm front. When the cold front overtakes the warm front, it forces both the warm air and the cooler air aloft.
Weather: Expect intense weather near the front, such as thunderstorms, heavy rain, and strong winds, especially in areas of rising warm air. Post-frontal conditions often bring colder, drier air and clearing skies.
More dramatic with cumulonimbus clouds, heavy precipitation, and potential thunderstorms.
Warm Occluded Front
Description: The air behind the cold front is milder than the cold air ahead of the warm front. When the cold front overtakes the warm front, the cooler air ahead of the front remains near the ground, forcing the milder air aloft.
Weather: Precipitation is often widespread but less intense compared to a cold occlusion. Clouds and steady rain or drizzle are common, with possible fog due to the mixing of air masses.
Typically associated with nimbostratus or stratus clouds, lighter precipitation, and overcast conditions.
What are general weather characteristic of a cold front? Warm front?
Cold front
-usually associated with hazardous weather, turbulence, winds, precipitation
-Can be fast or slow moving fast is more hazardous as edge is steeper
-Lifts warmer air ahead, pass quickly and weather doesnt last followed by dry air with good visibility
Warm front
-slower moving, tends to linger for days
-warm air overtakes colder airmass, slope is more gradual
-can find steady precipitation and light to no turbulence ahead of warm front
Define density Altitude
Density altitude is pressure altitude corrected for non-standard temp.
-under standard atmospheric conditions air at each level in atmosphere had specific
density, pressure altitude and density altitude identify the same level
-Therefor, density altitude is the vertical distance above sea level in standard atmosphere at which a given density is found
The amount of moisture in the air is dependent on what feature?
The air temperature
-every 20°f increase in temperature doubles the amount of moisture the air can hold
-a decrease of 20°f cuts the capacity in half
What is the standard temperature and pressure at sea level
Standard temperature is 15°c or 59°f decreasing at a rate of 2°C or 3°F for every 1000’ gained
Standard air pressure - at sea level is 29.92Hg
(unfinished )What point of a microbus is the most dangerous
When experiencing a tailwind the plane cannot create enough uplifting force
Define wind shear
A sudden drastic change in wind speed and or direction over a very small area
can occure at any altitude, but especially hazardous to aircraft operating on ground
can subject aircraft to violent updrafts and downdrafts as well as abrupt changes in horizontal movement
how does air flow in a low pressure system in the northern hemisphere work? High pressure system?
Low pressure - inward, upward, counterclockwise
High pressure - outward, downward, clockwise
How does density altitude affect aircraft performance?
Density altitude will increase (low air density) when one or more of the following occurs
high air temp
high altitude
hi humidity
Density altitude will decrease (high air density) when one or more of the following occurs:
low air temp
low altitude
low humidity
Ceilings and visibility for VFR
VFR is a ceiling greater than or equal to 3,000 AGL and visibility greater than or equal to 5mi
MVFR is ceiling of 1000 - 3000 with visibility 3 - 5 miles
VFR must remain clear of clouds
What 3 ingredients are necessary for precipitation to form?
Precipitation formation needs 3 ingredients:
water vapors
sufficient lift to condense the vapor into clouds
a growth precess that allows cloud droplets to grow large and heavy enough to fall as precipitation
significant precipitation usually requires clouds to be at lease 4,000 thick
Define relative humidity and dew point
Relative humidity - the ration usually expressed as a percentage of water vapor actually in the air parcel compared to the amount of water vapor the air parcel could hold at a particular temp and pressure
Dew point - the temp an air parcel must be cooled at constant pressure and constant water vapor pressure to allow the water vapor in the parcel to condense into water
Occluded front
a frontal occlusion occurs when a fast moving cold front catches up with a slow moving warm front. the two types are the cold front occlusion and warm front occlusion
Stratiform
Stratus is latin for “layer” or “blanket”
these clouds consist of a featureless lower layer that can cover the entire sky like a blanket
the cloud bases are usually only a few hundred feet above ground
What factors affect air density?
Attitude - the higher the altitude the less dense the air
Temperature - the warmer the air the less dense it is
humidity - more humid air is less dense
What is a flight service broadcast (FIS - B)
A ground based broadcast service provided through the automatic dependent surveillance - broadcast (ADS -B) universal access transceiver network (UAT)
FIS - B enables users of property equipped aircraft the relieve and display a suite of broadcast weather and aeronautical info products
Not appropriate for tactical avoidance of severe weather such as negotiating a path through a weather hazard area
What does a standard brief include?
The briefer will provide the following info in sequence
adverse conditions
vfr flight not recommended
synopsis
current conditions
enroute conditions
destination forecast
winds aloft
notams
atc delays
other info
What type of weather briefings are available from an AFSS/FSS briefer
Standard briefing - request when you are planning a flight and have not recieved a previous briefing or preliminary info through online sources
abbreviated briefing - request when you need info to supplement mass data, update previous briefing, or need one or two items
outlook briefing - request when your proposed departure time is 6 or more hours away, for planning
inflight briefing - request when needed to update a preflight briefing
Does FAA consider weather self briefing complaint with regulations?
According to the FAA a self briefing may be compliant with current federal aviation regulations
Does weather info from commercial or third party vendors satisfy preflight required by 91.103
No, entities other than FAA or NWS or their contractors may not meet FAA/NWS quality control standards
when in doubt, consult with FAA flight service specialist
Two main categories of sources of weather data?
Federal Govt. - the FAA National weather service collect weather observations the NWS analysis the data and produces forecast using a variety of systems.
the FAA is the only opproval authority for sources of weather observations
commercial weather info providers - repackage propiotary weather products based on NWS info with modefied layout but no material changes to weather info. other commercial providers produce forecast / analysis that may differ from NWS
What service does FAA provide for pilots to obtain a weather briefing
The FAA provides the flight service program, which provides weather briefings to pilots through its flight service station
1800 WX Brief
1800wxbrief.com
Troposphere
The first layer is the troposphere, extending from 4-12 miles over north/south poles and 48,000’ over equatorial regions
the vast majority of weather clouds storms and temp variance occur within this layer
inside the troposphere the average temp decreases at a rate of 2°C every 1000 of altitude gain
the pressure decreases at a rate of 1” per 1000’ of altitude gain
Extends up to 20,000 - 56,000 so 33,000 avg
Tropopause
A top of the troposhere is a boundary callded the tropopause which traps moisture and associated weather in the troposphere. the altitude of the tropopause varies with latitude and season of the year; therefor it takes on an eliptical shape
location of the tropopause is important because it is commonly associated with the location of the jet stream and possible clear air turnulence
Stratophere
mesophere
thermosphere
Above the tropopause are 3 more atmospheric layers.
the first is the stratosphere, which extends from the tropopause to about 160,000’. little weather exists in this layer and air remains stable.
above the stratosphere is the mesophere, reaching 280,000’ and the thermosphere above that, which have little influence over weather
Composition of the atmosphere
In any given volume of air, nitrogen accounts for 78% of the gases that comprise the atmosphere, while oxygen makes up of 21%. other traces gases like CO2 make up the last 1%
this volume of air also contains water vapor. from 0-5% this small amount of water vapor is responsible for major changes in weather.
the envelope of gasses surrounding earth changes from the ground up. Four distinct layers of speres of the atmosphere have been identified using thermal charecteristics, chemical composition, movement and density
Atmospheric circulation
The atmosphere is in a constant motion
the major factor in atmospheric motion is the uneven heating of earths surface
this heating upsets the equilibrium of the atmosphere creating changes in air movenent and atmospheric pressure
The movement of air aroudn earths surface is called atmospheric circulation
Wind and currents
Air flows from areas of high pressure into areas of low pressure because air always seeks lower pressure.
the combination of atmospheric pressure differences, coriolis force,friction, and temp differences of the air near the earth causes two kinds of atmmospheric motion:
convective currents - upward and downward motion
wind - horizontal motion
currents and winds or atmospheric circulations cause weather changes and affect takeoffs, landings, and cruise flight operations
Wind Patterns
In northern hemisphere, the flow of air from areas of high to low pressure is deflected to the right and produces a clockwise circulation around the area of high pressure. this is known as anticyclonic circulation
the opposite is true of low pressure areas: the air flows towards a low and is deflected to create a counterclockwise or cyclonic circulation
HP system are generally dry, desecending air and typically associated with good weather
LP systems - air flows into LP to replace rising air, usually bringing clouds and precipitation. Associated with bad weather
