Aviation Weather Handbook Study Notes

Aviation Weather Service Program

  • Joint Effort: Collaborative program between NOAA, FAA, DOD, NASA, and commercial providers.

  • Key NOAA Entities:
        * National Weather Service (NWS): Provides data, forecasts, and warnings.
        * Aviation Weather Center (AWC): Issues AIRMETs, SIGMETs, and global Significant Weather (SIGWX) forecasts.
        * Space Weather Prediction Center (SWPC): Monitors solar activity affecting COM/NAV.

  • Key FAA Facilities:
        * ARTCC/ATCT: Provide en route and terminal ATC services and hazardous weather advisories.
        * Flight Service: Offers pre-flight briefings (1-800-WX-BRIEF) and in-flight updates.

Weather Theory

  • Atmospheric Structure: Divided into the Troposphere (where most weather occurs), Stratosphere (inversions/stable), Mesosphere, Thermosphere, and Exosphere.

  • The Standard Atmosphere: Hypothetical model used for altimetry/performance. Sea level: 1013.25 hPa1013.25\,hPa (29.92 inHg29.92\,inHg) and 15 ∘C15\,^{\circ}C (59 ∘F59\,^{\circ}F).

  • Stability:
        * Stable: Resists vertical motion; associated with stratiform clouds/fog.
        * Unstable: Accelerates vertical motion; associated with cumuliform clouds/convection.

  • Adiabatic Processes: Unsaturated air cools at 3 ∘C/1,000 ft3\,^{\circ}C/1,000\,ft (dry lapse rate); saturated air cools at approximately 2 ∘C/1,000 ft2\,^{\circ}C/1,000\,ft (moist lapse rate).

Aviation Weather Hazards

  • Thunderstorms: Require moisture, instability, and a lifting mechanism. Life cycle: Towering Cumulus, Mature (precipitation begins), and Dissipating.

  • Icing:
        * Rime: Brittle/opaque; forms from small droplets.
        * Clear: Glossy/transparent; common with Supercooled Large Drops (SLD). Higher wing-load hazard.
        * Mixed: Combination of rime and clear.

  • Turbulence: Caused by convection, mechanical obstructions (mountains), or wind shear (CAT).

  • Altimetry Errors:
        * High to Low Pressure: Aircraft is lower than altimeter indicates.
        * Warm to Cold Temp: Aircraft is lower than altimeter indicates.

Weather Observations and Products

  • METAR/SPECI: Primary surface observation format. Includes wind, visibility, weather, sky condition, and altimeter setting.

  • PIREPs: Pilot reports defined as Routine (UA) or Urgent (UUA).

  • Radar (WSR-88D): Measures reflectivity (dBZdBZ) to determine precipitation intensity. Limitations include beam blockage, attenuation, and the "cone of silence."

  • Satellite: Includes GeoColor (day/night mix), Visible (day only), and Infrared (cloud top temperatures).

  • TAF: Terminal Aerodrome Forecast describing conditions within 5 SM5\,SM of an airport.

  • AIRMETs:
        * Sierra: IFR/Mountain Obscuration.
        * Tango: Turbulence/Sustained Wind > 30 kt30\,kt/Wind Shear.
        * Zulu: Icing/Freezing Levels.

  • SIGMETs: Issued for severe hazards (e.g., severe icing/turbulence, volcanic ash, tropical cyclones).