Aeronautical Weather Reports Flashcards
Sources of Weather Data
using 1800wxbrief (for stage check) be able to make a go or no-go decision based on a weather briefing: helpful weather charts
Sources of Weather Data:
- 1800wxbrief
- FSS
- Aviationweather.gov
- NWS Office
- AWOS/ASOS/ATIS
- METAR- reports every hour unless SPECI METAR for significant weather change
- TAF (Terminal Aerodrome Forecast)- reports forecast for 5 NM radius of an airport, Valid for 24-30 hours (reports 4X a day or every 6 hours)
Standard Atmosphere
59F or 15C, 29.92 Hg or 1013.2 mbar
What is Pressure Altitude?
the height above the standard datum plane
- Level where pressure is 29.92 Hg
important for determining aircraft performance
What is Density Altitude?
It correlates aerodynamic performance with non-standard atmosphere temperature
- Has significant effects on aircraft performance: as air becomes less dense it reduces power (engine takes less air), thrust (prop is less efficient in thin air), lift (thin air exertsless force on airfoils)
Low DA = high performance
High DA = low performance
- Density is affected by change in altitude/pressure, temperature, and humidity Ex:
EX: High DA = low pressure, high temp, high humidity
Standard Lapse Rate
^1,000ft temp -2C
^1,000ft pressure -1 HG
Pressure Systems (how do they work?)
air flows from high to low pressure areas
Low Pressure Systems
A mass of air that is less dense than surrounding air
- Associated with bad weather, warm temps, high humidity
- Flows counter-clockwise, inward, and upward (cyclonic)
High Pressure System
A mass of air that is more dense than surrounding air
- Associated with good weather, lower temps, low humidity
- Flows clockwise, outward, and downward (anticyclonic)
Isobar
line connecting areas of constant (equal) pressures
Pressure Gradient Force (PFG)
A horizontal spacing of isobars
- Sets wind and puts air in motion, driven by pressure differences
- When a pressure difference develops over an area the PGF causes wind to blow in
order to equalize the pressure
- Flows toward low and away from high pressure
- The closer isobars are, the more gradient of pressures, the faster the wind speeds
Air Mass
has uniform temp, dew point, wind and pressure
Weather Front
A Boundary layer between two air masses
4 Types of Fronts
Cold, Warm, Stationary and Occluded
Cold Fronts
air mass of cold, dense, stable air advances and displaces warmer air
- Fast moving, slides under warm air mass and forces it aloft
- Before the front arrives expect high dew point and falling pressure
- After the front passes except the weather to clear quickly, good visibility, colder
temperatures, and rising pressure
- Associated weather: thunderstorms, heavy showers, poor visibility, gusty winds
depicted as ice icicles (blue)
Warm Fronts
-warm mass overtakes and replaces colder mass
- Slow moving, gradually sloping mass slides over top of cold mass
- Takes days to pass but expect precipitation, low visibility, stratiform clouds followed by
warmer temperatures, clear skies, high humidity
- Associated weather: stratiform, drizzle, haze, fog
depicted as suns (red)
Stationary Fronts
When opposing forces of two air masses are equal
- Very slow moving
- Weather is a mix of warm and cold fronts
mix of red (suns) and blue (ice icicles)
Occluded Front
A fast moving cold front catches up to slow warm front
- Associated weather: thunderstorms, rain, poor visibility, nasty weather you DO NOT want to fly into
Purple sun and ice icicle imagery
Thunderstorm Dangers
- Lightening
- Adverse winds/windshear
- Microbursts
- Turbulence
- Icing
- Hail
Stages of a Thunderstorm
Cumulus Stage: lifiting action (strong updrafts) Building Clouds
Mature Stage: (most violent) percipitation starts; now strong downward motions & upward moiton (HEAVY TURBULANCE)
Dissipating Stage: anvil shape, downdrafts cause cloud to spread out. (updrafts gone)
Humidity
the amount of moisture in the air
Relative Humidity
the actual amount of moisture, compared to the total that could be present at current temperature (temp and dew point spread)
Types of Weather Briefings
Standard:
designed for flights due to depart in 6hrs
Abbreviated:
an updated breifing right before you go
Outlook:
appropriate when the departure is more than 6hrs from the time of the breifing
Airmets & Types of Airmets
AIRMET- valid 6 hours, Weather may be hazardous to single engine, light, and VFR
aircraft (for ALL Aircraft but mostly G.A. Aircraft)
Sierra- IFR conditions and/or extensive mountainous obscurations
Tango- moderate turbulence, sustained surface winds of 30kts or more, and/or non-convective low level windshear
Zulu- moderate icing and freezing level heights
Sigmet
SIGMET- valid 4 hours, weather potentially hazardous to all aircraft may include:
- Severe icing not associated with thunderstorms
- Severe turbulence not associated with thunderstorms
- Dust/sand storm
- Volcanic ash
NOT ASSOCIATED WITH THUNDERSTORMS!
Convective SIGMET
Convective SIGMET- valid 2 hours
- Severe thunderstorm with wind greater than 50kts, 3⁄4 inch hail, or tornadoes
Can include:
- Thunderstorm- producing precipitation affecting 40% or more of a 3000 mile area
- Embedded thunderstorm- last more than 30 minutes
- Line of thunderstorms (squall line)- 60 miles long, 40% affected by precipitation
Types of Weather Briefings and When do you need each them?
Outlook: +6 Hours out from Departure time limited weather information good for planning in advance
Standard: -6 Hours from Departure time
a comprehensive briefing that compares your flight plan to the current weather and forecasts
Abbreviated: At departure (Updated)
a quick update to a standard briefing
