AIRMETs and SIGMETs

Private Pilot License (PPL) Notes

This section introduces AIRMETs, SIGMETs, and Convective SIGMETs, which are essential weather forecast products that help pilots identify hazardous conditions along their planned routes.

Understanding Weather Hazards:

1. Common weather hazards include:
   1. Turbulence
   2. Wind shear
   3. Icing
   4. Fog
   5. Thunderstorms
2. The National Weather Service provides forecast products to alert pilots of these hazards:
   1. AIRMETs
   2. SIGMETs
   3. Convective SIGMETs

AIRMETs (Airman's Meteorological Information):

1. Designed to alert VFR pilots and light aircraft of hazardous conditions.
2. Originally text-based but now available as Graphical AIRMETs (G-AIRMETs):
   1. Provide better visual representation on a map.
   2. Include shorter forecast intervals of 3 hours for accuracy.
3. AIRMETs are issued for:
   1. IFR conditions (ceilings less than 1,000 ft and/or visibility less than 3 statute miles).
   2. Widespread mountain obscuration.
   3. Moderate icing and freezing levels.
   4. Moderate turbulence.
   5. Potential non-convective low-level wind shear below 2,000 ft AGL.
4. Example of an AIRMET:
   1. Issued for moderate turbulence across the upper Midwest.
   2. Expect turbulence from the surface up to 18,000 ft.

SIGMETs (Significant Meteorological Information):

1. Issued to advise all aircraft of severe weather conditions affecting safety.
2. SIGMETs cover hazards such as:
   1. Severe or greater turbulence.
   2. Severe icing.
   3. Widespread dust storms or sandstorms.
   4. Volcanic ash.
3. Valid for up to 4 hours and include graphical and text descriptions.
4. Example of a SIGMET:
   1. SIGMET Quebec 9 issued for severe turbulence in the southern U.S.
   2. Valid from 17:10 Zulu to 21:10 Zulu.
   3. Expect severe turbulence between FL220 and FL310 due to wind shear associated with the jet stream.
   4. Conditions reported by other aircraft and expected to continue beyond the valid time.

Convective SIGMETs:

1. Issued when severe conditions exist due to thunderstorms.
2. Imply severe or greater turbulence, severe icing, and low-level wind shear.
3. Issued hourly for:
   1. Lines of thunderstorms.
   2. Embedded thunderstorms lasting longer than 30 minutes.
   3. Areas of active thunderstorms affecting 40% or more of an area.
4. Special Convective SIGMETs issued for:
   1. Tornadoes.
   2. Thunderstorms with surface winds of 50 knots or more.
   3. Hail ¾ inch in diameter or larger.
5. Example of a Convective SIGMET:
   1. Convective SIGMET 69 Charlie for a line of storms over Louisiana and Mississippi.
   2. Severe thunderstorms moving east at 25 knots with tops above 45,000 ft.
   3. Includes threats of hail up to 1 inch and wind gusts up to 50 knots.

Accessing Weather Hazard Information:

1. Using the Aviation Weather Center website:
   1. Homepage displays a big-picture view of U.S. weather hazards.
   2. Click on the map to access the full-screen interactive map.
   3. Select 'G-AIRMET' from the 'Products' menu to view current AIRMETs.
   4. Use the 'Layers' button to focus on specific hazards (e.g., Turbulence Low).
   5. Click on affected areas for detailed forecast information.
   6. Use the altitude slider to filter AIRMETs by altitude relevant to your flight.
2. Viewing SIGMETs and Convective SIGMETs:
   1. Select 'SIGMETs' from the 'Products' menu to view current SIGMETs.
   2. Convective SIGMETs are also displayed and can be viewed alongside radar imagery.
   3. Access the 'Observations' map page under the 'Weather' menu for radar and convective SIGMETs.
   4. Click on SIGMET areas for details including storm movement and thunderstorm tops.
3. Using ForeFlight app:
   1. Enable 'AIR/SIGMET/CWA' layer in the map layers menu.
   2. Use the buttons at the bottom of the screen to focus on specific hazards:
      1. Ice
      2. High-altitude turbulence
      3. Low-altitude turbulence
      4. IFR conditions
      5. Thunderstorms
   3. AIRMETs are shown in orange, SIGMETs in red.
   4. Tap on hazard areas to view detailed information.

Understanding and regularly checking AIRMETs and SIGMETs is crucial for flight safety. Always include these weather hazard products in your pre-flight planning to ensure a safe journey.