{{Short description|Moderate flight weather advisory}} [[File:G-AIRMET 2024-12-30-09Z.gif|thumb|Graphical AIRMET showing turbulence high (TurbHi), turbulence low (TurbLo), surface wind (sfcWind), and low-level wind shear (LLWS) over the coterminous United States]] {{Aviation Briefing navbox}} An '''AIRMET''', or '''Airmen's Meteorological Information''', is a concise description of weather phenomena that are occurring or may occur (forecast) along an air route that may affect aircraft safety. Compared to SIGMETs, AIRMETs cover less severe weather: moderate turbulence and icing, sustained surface winds of 30 knots or more, or widespread restricted visibility. Today, according to the advancement of technology in civil aviation, the AIRMET is sent as IWXXM model.<ref name=":0">{{Cite journal |last1=Latifiyan |first1=Pouya |author-link1=Pouya Latifiyan |last2=Entezari |first2=Mojtaba |date=March 2024 |title=IWXXM Amendment (ICAO Meteorological Information Exchange Model) |url=http://dx.doi.org/10.13140/RG.2.2.12572.30088 |journal=CATC Robex and Statics Conferences - 2024 |language=En |location=Tehran, Iran|doi=10.13140/RG.2.2.12572.30088 }}</ref>
== Types ==
AIRMETs are broadcast on the ATIS at ATC facilities, and are referred to as '''Weather Advisories'''. AIRMETs are valid for six hours.<ref>ICAO Annex 3 Chapter 7</ref> NOTE: The definition has changed and no longer says "light aircraft"; AIRMETs are intended for ''all'' aircraft.
There are three types of AIRMET, all identified by a phonetic letter: S (Sierra), T (Tango), and Z (Zulu).<ref>[https://web.archive.org/web/20120726013603/http://www.faa.gov/air_traffic/publications/atpubs/aim/aim0701.html Chapter 7. Safety of Flight]</ref>
* '''AIRMET SIERRA''' (Mountain obscuration or IFR) ceilings less than 1000 feet and/or visibility less than 3 miles affecting over 50% of the area at one time; extensive mountain obscuration *'''AIRMET TANGO''' (Turbulence) moderate turbulence, sustained surface winds of 30 knots or greater, and/or non convective low−level wind shear. *'''AIRMET ZULU''' (Icing) Moderate icing and provides freezing level heights.
For an authority to issue an AIRMET, applicable conditions must be widespread. "Widespread" means that the applicable area covers at least 3000 square miles. Because conditions across the forecast period can move across the area, it is possible that only a small portion of the area is affected at any time. AIRMETs are routinely issued for six-hour periods beginning at 0145Z during Daylight Saving Time and at 0245Z during Standard Time. AIRMETS are also amended as necessary due to changing weather conditions or issuance/cancellation of a SIGMET.
== Dissemination and structure == {{See also|SIGMET#Structure}}
Most AIRMET dissemination is done in the XML-based Graphical AIRMET (G-AIRMET) format, but some computer systems use the legacy text-based Traditional Alphanumerical Code (TAC). This is identical in structure to a SIGMET, with the only difference being that the <code>SIGMET</code> identifier in the First Line is replaced by the three type identifiers listed above.<ref name=faa>{{cite web|title=Pilot's Handbook of Aeronautical Knowledge|url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/|publisher=Federal Aviation Administration|access-date=17 September 2019}}</ref>
The TAC AIRMET is being retired,<ref>{{cite news |last1=Dennstaedt |first1=Scott |title=Say Goodbye to the Traditional AIRMET |url=https://www.flyingmag.com/say-goodbye-to-the-traditional-airmet/ |access-date=26 November 2024}}</ref> and only G-AIRMETs will be disseminated for the continental US starting on or about January 27, 2025.<ref>{{cite web |title=Service Change Notice 24-92 |url=https://www.weather.gov/media/notification/pdf_2023_24/scn24-92tac_airmet_retirement.pdf |access-date=26 November 2024 |date=26 November 2024}}</ref>
==References== {{reflist}}
==External links== * {{cite web |url= http://www.faa.gov/air_traffic/publications/atpubs/aim/aim0701.html |url-status= |archive-date= July 26, 2012 |archive-url= https://web.archive.org/web/20120726013603/http://www.faa.gov/air_traffic/publications/atpubs/aim/aim0701.html |title= FAA Aeronautical Information Manual |id= Ch 7 "Safety of Flight", Section "Meteorology" |publisher= FAA }} * {{cite web |url= https://www.weather.gov/source/zhu/ZHU_Training_Page/Weather_Keys/AIRMETs/AIRMET.htm |title= What is an AIRMET |publisher= National Weather Service |location= Aviation Weather Center, Kansas City, Missouri |series= ZHU training }} * {{cite web |url= http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/6A07EFAA9A68C1A8862576C70052E9E5?OpenDocument |url-status= dead |title= AIRMET |publisher= FAA |series= Advisory Circular |id= AC 00-45G |location= Aviation Weather Services |website= Regulatory and Guidance Library (RGL) |archive-date= March 1, 2013 |archive-url= https://web.archive.org/web/20130301232944/http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/6A07EFAA9A68C1A8862576C70052E9E5?OpenDocument }} * Graphical representation of AIRMETs can be found at: [https://www.aviationweather.gov/ AWC - Aviation Weather Center]. Select the G-AIRMET checkbox for "Graphical AIRMET".
Category:Aviation meteorology Category:Weather warnings and advisories Category:Aviation publications
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