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)
