Aviation Weather Overview

Overview

This handbook is a comprehensive guide to U.S. aviation weather programs, products, theory, hazards, and tools, designed to support safe flight operations and informed decision-making for pilots and aviation professionals.

Aviation Weather Service Program

• Aviation weather services are provided by NOAA, FAA, DOD, and commercial providers.
• NOAA’s NWS, NESDIS/SAB, and NCEP centers offer core aviation weather products.
• FAA facilities (ATCSCC, ARTCC, ATCT, TRACON, Flight Service) integrate weather for air traffic control and pilot services.
• Commercial providers repackage government data and may offer proprietary products.

Obtaining and Using Weather Information

• Pilots must review all available weather reports and forecasts before flight (per 14 CFR 91.103).
• Weather briefings: Standard, abbreviated, and outlook; available via phone, internet, or in person.
• Online tools and apps deliver regulatory-compliant briefings; self-briefing is encouraged.
• In-flight updates use FIS-B, ASOS/AWOS, ATIS, and Flight Service.

Weather Products and Elements

• Key products include METAR/SPECI, TAF, PIREP/AIREP, radar, satellite, AIRMETs, SIGMETs, CWAs, and more.
• Products address elements such as thunderstorms, wind, turbulence, icing, visibility, fog, freezing levels, and volcanic ash.
• Interactive online tools (GFA Tool, Flight Service Map) overlay multiple weather layers for situational awareness.

Weather Theory: Atmosphere, Heat, and Moisture

• The atmosphere consists mainly of nitrogen, oxygen, argon, and variable water vapor.
• Key layers: troposphere (weather), stratosphere (stable, little weather), mesosphere, thermosphere, exosphere.
• Heat transfer occurs via radiation, conduction, and convection; water’s high specific heat moderates temperature.
• The hydrologic cycle includes evaporation, condensation, precipitation, runoff, infiltration, plant uptake.

Pressure, Wind, and Circulation

• Atmospheric pressure decreases with altitude; measured in hPa, mb, or inHg.
• Wind results from pressure gradient force, Coriolis effect, and friction.
• Jet streams are high-altitude, fast-moving winds that influence weather patterns and flight.
• Local winds include sea breeze, land breeze, valley/mountain breezes.

Clouds, Stability, and Precipitation

• Clouds form through condensation in rising air; types depend on vertical motion, moisture, and stability.
• Atmospheric stability determines vertical air motion; classified as absolute, neutral, or conditional (unstable).
• Precipitation types: rain, snow, freezing rain, ice pellets, hail—depend on temperature profiles.

Hazards: Turbulence, Icing, Visibility, and More

• Turbulence arises from convection, terrain, and wind shear; classified as light, moderate, severe, or extreme.
• Icing forms from supercooled water droplets and is most hazardous between 0°C and -20°C.
• Visibility obstructions include fog, mist, haze, smoke, blowing snow, dust, sand, and volcanic ash.
• Special Arctic, mountain, and tropical weather effects create unique flight risks.

Aviation Weather Products: Types and Usage

• Observations: METAR, SPECI, ASOS, AWOS, PIREP, radar, satellite, weather cameras.
• Analyses: Surface/upper air charts, freezing/icing/turbulence analyses.
• Advisories: SIGMET (severe hazards), Convective SIGMET, AIRMET (moderate hazards), CWA, VAA, TCA, space weather, LLWS/microburst alerts.
• Forecasts: TAF, winds/temps aloft, area forecasts (FA), graphical/interactive tools, SIGWX, prog charts, icing/turbulence forecasts.

Key Terms & Definitions

• SIGMET — Advisory for severe weather hazards (e.g., turbulence, icing, volcanic ash).
• AIRMET — Advisory for moderate weather hazards (e.g., IFR, mountain obscuration, turbulence, icing).
• METAR/SPECI — Routine and special coded surface weather observations.
• TAF — Terminal Aerodrome Forecast, 24 to 30-hour forecast for airport vicinity.
• PIREP — Pilot Weather Report, in-flight weather conditions reported by pilots.
• GFA Tool — Graphical Forecasts for Aviation; interactive web-based weather visualization.
• FIS-B — Flight Information Service-Broadcast; transmits weather/advisory data to aircraft.
• Freezing Level — Lowest altitude where temperature is at or below 0°C.

Action Items / Next Steps

• Review local TAF, METAR, and AIRMET/SIGMET products for your route.
• Practice using the GFA Tool or Flight Service Interactive Map.
• Study Appendix A for cloud types and Appendix C for density altitude calculation.
• Stay current on updates to weather products and online tools.