Corrections to SIGMETs are issued as necessary. This is done by issuing a new SIGMET in the series, which advances the SIGMET number and cancels the previous SIGMET.

The ICAO communication header for this product is WVNT06. It is a SIGMET issued by the AWC (KKCI) in Kansas City, MO, on the eighth day of the month at 2030 UTC. This is the second issuance of SIGMET series Foxtrot valid from the 8th day of the month at 2030 UTC until the 9th day of the month at 0230 UTC. Within the San Juan Oceanic FIR, volcanic ash from the Soufriere Hills volcano located at 16°/42 minutes north, 62°/10 minutes west. Volcanic ash cloud observed at 2030 UTC within an area bounded by 17°/30 minutes north, 64°/00 minutes west to 17°/00 minutes north, 63°/00 minutes west to 16°/50 minutes north, 63°/00 minutes west to 17°/10 minutes north, 64°/00 minutes west to 17°/30 minutes north, 64°/00 minutes west. From the surface to 6,000 ft MSL. Moving to the west at 15 kt. Forecast at 0230 UTC, volcanic ash cloud located approximately at 17°/30 minutes north, 65°/00 minutes west to 17°/00 minutes north, 63°/00 minutes west to 16°/50 minutes north, 63°/00 minutes west to 17°/10 minutes north, 65°/00 minutes west to 17°/30 minutes north, 65°/00 minutes west.

The ICAO communication header for this product is WSNT03. It is a SIGMET issued by the AWC (KKCI) in Kansas City, MO, on the eighth day of the month at 1451 UTC. The NWS AWIPS communication header for this product is SIGA0C. This is the eleventh issuance of SIGMET series Charlie valid from the eighth day of the month at 1500 UTC until the eighth day of the month at 2100 UTC. Within the New York Oceanic FIR, Tropical Cyclone Kyle observed at 31°/6 minutes north, 71°/18 minutes west at 1500 UTC, cumulonimbus tops to FL500 (approximately 50,000 ft MSL), within 120 NM of the center, moving from west-southwest at 5 kt, no change in intensity is forecast, at 2100 UTC the tropical cyclone center will be at 31°/42 minutes north, 70°/12 minutes west.

An AIRMET is a concise description of the occurrence or expected occurrence of specified en route weather phenomena which may affect the safety of aircraft operations. AIRMETs are intended to inform all pilots, especially VFR pilots and operators of sensitive aircraft, of potentially hazardous weather phenomena. AIRMETs contain details about IFR, extensive mountain obscuration, moderate turbulence, strong surface winds, moderate icing, and freezing levels.

AIRMETs are intended for dissemination to all pilots in the preflight and en route phases of flight to enhance safety. En route, AIRMETs are available over Flight Service frequencies. Over the CONUS, AIRMETs are also available on equipment intended to display weather and other non-ATC-related flight information to pilots using the FIS-B. In Alaska and Hawaii, AIRMETs are broadcast on air traffic frequencies.

AIRMETs are issued for the CONUS, Alaska, and Hawaii. No AIRMETs are issued for U.S. Oceanic FIRs in the Gulf of America, Caribbean, and Western Atlantic and Pacific Oceans.

AIRMETs are issued from the three U.S. MWOs located at the AWC, the AAWU, and the WFO Honolulu. Their areas of responsibility are:

AIRMETs over the CONUS are displayed graphically (sometimes known as G-AIRMETs) on websites such as https://aviationweather.gov and https://www.1800wxbrief.com and equipment receiving FIS-B information. AIRMETs over the CONUS provide a higher forecast resolution than AIRMETs issued in text format. AIRMETs over the CONUS are valid at discrete times no more than three hours apart for a period of up to 12 hours into the future (e.g., 00, 03, 06, 09, and 12 hours). Additional forecasts may be inserted during the first six hours (e.g., 01, 02, 04, and 05). A forecast at 00-hour represents the initial conditions, and the subsequent graphics depict the area affected by the particular hazard at that valid time. Forecasts valid at 00 through 06 hours correspond to the text AIRMET bulletin.

AIRMETs over the CONUS depict the following en route aviation weather hazards:

Interpolation of time periods between AIRMETs over the CONUS valid times: Users should keep in mind when using the AIRMET over the CONUS that if a 00-hour forecast shows no significant weather and a 03-hour forecast shows hazardous weather, they must assume a change is occurring during the period between the two forecasts. It should be taken into consideration that the hazardous weather starts immediately after the 00-hour forecast, unless there is a defined initiation or ending time for the hazardous weather. The same would apply after the 03-hour forecast. The user should assume the hazardous weather condition is occurring between the snapshots unless informed otherwise. For example, if a 00-hour forecast shows no hazard, a 03-hour forecast shows the presence of hazardous weather, and a 06-hour forecast shows no hazard, the user should assume the hazard exists from the 0001-hour to the 0559-hour time period.