An AIRMET (Airmen's Meteorological Information) is a type of weather advisory issued by national meteorological agencies to provide information about potentially hazardous weather conditions for flight operations.
AIRMETs are used to inform pilots and air traffic control personnel about conditions that are less severe than those described in a SIGMET (significant meteorological information), but which can still pose a risk to flight operations.
The information contained in an AIRMET includes the location, size, and movement of the weather phenomenon, as well as the intensity and type of weather associated with it. This information is critical for pilots and air traffic control personnel to have, as it helps them make informed decisions about flight plans, altitudes, and routes.
When AIRMETs are Issued?
The purpose of AIRMET information is to advise pilots of the occurrence or expected occurrence of specified en-route weather phenomena which may affect the safety of low-level aircraft operations and which were not already included in the forecast (GAMET or Low-Level SIGWX charts) issued for low-level flights in the FIR concerned or sub-area thereof.
AIRMETs are typically issued during the following weather conditions occur or are expected to occur,
Moderate Icing (MOD ICE) - Freezing Level Altitudes (FRZLVL)
Moderate Turbulence (MOD TURB)
Moderate Moutain Waves (MOD MTW)
Surface Wind speed greater than 30 Knots (SFC WSPD)
Ceiling less than 1000 Feet / or visibility less than 3 miles affecting over 50 per cent of the area at one time. (IFR)
Widespread mountain obscurations (MTN OBSCN)
As per ICAO definition, Isolated or Occasional Thunderstorms, Cloud Types such as Cumilonnimbus or Towering cumulus also will be included in the report.
These conditions can be hazardous for flight operations and can cause discomfort for passengers, but they are typically less severe than those described in a SIGMET.
How to Read AIRMET?
The format of an AIRMET report typically consists of several key elements that provide important information to pilots about the current weather conditions. These elements can include:
Area of coverage: AIRMETs are issued for specific regions and provide the boundaries of the area that is affected.
Product Details: Product Name such as AIRMET, AIRMET Series (Only for the United States), Update Number, Product Description.
Following the AIRMET series used in the united states,
SIERRA - For Instrument Flight Rules (IFR) and Mountain Obscurations
TANGO - Moderate Turbulence, Surface Wind Greater than 30 Knots, Non-convective low-level wind shear
ZULU - Moderate Icing and Freezing Level Heights
Valid time: AIRMETs are valid for a specific time period, usually 6 hours, and indicate when the information contained in the report is current.
Type of weather phenomenon: AIRMETs provide information on specific weather conditions such as turbulence, icing, low-level wind shear, and other weather phenomena.
Intensity and altitude: AIRMETs typically indicate the intensity of the weather condition and the altitude range where it is likely to occur.
Forecast trends: AIRMETs may provide information on the expected trend of the weather conditions, such as if they are expected to increase or decrease in intensity.
Additional information: AIRMETs may also contain additional information such as a description of the location of fronts, pressure systems, or other weather features that could impact flight safety.
Here is an example of AIRMET message,
AIRMET TANGO UPDT 1 FOR TURB AND ICE VALID UNTIL 181500
... TEXAS ...
MOD TURB BTN FL240 AND FL360. CONDS ENDING 18Z.
MOD ICE BTN 070 AND FL180. CONDS CONTG BYD 18Z.
... OKLAHOMA ...
MOD TURB BTN FL240 AND FL360. CONDS CONTG BYD 18Z.
... ARKANSAS ...
MOD TURB BLW FL240. CONDS CONTG BYD 18Z.
... REMAINDER OF TEXAS AND OKLAHOMA ...
NO SGFNT TURB EXPECTED.This AIRMET is designated as "TANGO UPDT 1" and is valid until 181500 (18th day of the month, at 1500 UTC). It is issued for turbulence and icing conditions in the affected areas, which in this case include Texas, Oklahoma, and Arkansas.
The AIRMET reports that there is moderate turbulence between flight levels 240 and 360 in Texas and Oklahoma, and that these conditions are expected to continue until 18Z (18:00 UTC). In Arkansas, there is moderate turbulence below flight level 240, also expected to continue until 18Z.
Additionally, there is moderate icing between 70 and flight level 180 in Texas, expected to continue beyond 18Z.
For the remainder of Texas and Oklahoma, no significant turbulence is expected.
This is a sample AIRMET and the actual AIRMET issued by the NWS may vary based on the specific weather conditions in the affected area.
However, the information included in an AIRMET is typically consistent and provides important information to pilots about the weather conditions they may encounter during their flight.
Conclusion
Like SIGMETs, AIRMETs are typically updated as new information becomes available, and they are broadcast to all relevant aviation stakeholders in a timely manner. AIRMETs are an important tool for ensuring aviation safety, and they are widely used by aviation professionals around the world.
AIRMETs play a critical role in ensuring the safety of flight operations by providing pilots and air traffic control personnel with important information about adverse weather conditions. By making informed decisions based on AIRMET information, aviation professionals can help to ensure the safety and comfort of both crew and passengers.