AIRMETs, SIGMETs, PIREPs and weather charts
9 min readLesson 44 of 59
By the end of this lesson you'll be able to:
- Tell AIRMETs, SIGMETs and convective SIGMETs apart
- Read and file a PIREP
- Use the GFA, surface analysis and prog charts
In-flight weather advisories
| Advisory | For |
|---|---|
| AIRMET Sierra | IFR conditions (ceilings below 1,000 ft and/or visibility below 3 SM) over a wide area, and mountain obscuration |
| AIRMET Tango | Moderate turbulence, sustained surface winds of 30 knots or more, low-level wind shear |
| AIRMET Zulu | Moderate icing and freezing levels |
| SIGMET | Severe icing, severe or extreme turbulence, dust or sandstorms lowering visibility below 3 SM, volcanic ash. Hazardous to all aircraft. |
| Convective SIGMET | Thunderstorms (severe, embedded, lines or widespread areas), tornadoes, and hail 3/4 inch or larger. Implies severe turbulence, icing and wind shear. |
AIRMETs are especially important to light airplanes, because what's "moderate" for an airliner can be serious for a Cessna 172.
PIREPs
Pilot reports (PIREPs) are the only way to know what's actually happening up there, like cloud tops, turbulence and icing. "UA" is a routine report and "UUA" is urgent. Give them to ATC or Flight Service, and use them when you plan. When you see something interesting, report it; other pilots will thank you.
Weather charts and graphics
- Graphical Forecasts for Aviation (GFA): the FAA's web tool showing observations, forecasts of clouds, weather, turbulence and icing over time. It replaced the old text area forecast.
- Surface analysis chart: current fronts, pressure systems and station reports.
- Prognostic (prog) charts: forecast fronts, pressure systems and weather areas for the next few days.
- Radar and satellite: where precipitation is now, and where the clouds are. Radar shows precipitation, not clouds.
Key takeaways
- AIRMETs: Sierra (IFR, mountain obscuration), Tango (turbulence, winds, LLWS), Zulu (icing).
- SIGMETs = severe hazards to all aircraft; convective SIGMETs = thunderstorms.
- PIREPs are the best information about actual conditions; give them too.
What the examiner may ask
Practice answering out loud before you open each answer.
Which AIRMET would you check for turbulence?
AIRMET Tango.
What's the difference between an AIRMET and a SIGMET?
AIRMETs cover hazards mainly to light aircraft (moderate icing, moderate turbulence, IFR); SIGMETs cover severe hazards to all aircraft.
What does radar show, and what doesn't it?
Radar shows precipitation, not clouds; light drizzle or clouds without precipitation may not appear.
Common mistakes
- Ignoring AIRMET Sierra for mountain obscuration on a mountain route.
- Assuming a clear radar picture means no clouds.
- Not filing PIREPs.
Read it in the FAA sources
Lesson check
Get every question right to complete the lesson. Take your time; wrong answers explain why.
Something wrong or out of date? Report an error