What is an AIRMET?

An AIRMET is an advisory that includes hazardous weather phenomena for light aircraft.

An AIRMET is issued every six hours with updates issued as needed.  The information in an AIRMET is of operational interest for all aircraft, but the weather section includes potentially hazardous phenomena for light aircraft.  Three types of AIRMETs are listed below.

AIRMET Sierra describes IFR (instrument flight rules) conditions and/or extensive mountain obscurations.

AIRMET Tango describes moderate turbulence, sustained surface winds of 30 knots or greater, and Non-Convective low-level wind shear.

AIRMET Zulu describes moderate icing and provides freezing-level heights.

Reference(s):

FAA AC 00-45H Aviation Weather Services pg. 5-16, 5-21
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-8

Other Aviation Weather Services

What is a SIGMET?

SIGMETs are inflight advisories concerning non­convective weather that is potentially hazardous to all aircraft.

SIGMETs report weather forecasts that include severe icing not associated with thunderstorms, severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms, dust storms or sandstorms that lower surface or inflight visibilities to below three miles, and volcanic ash.  SIGMETs are unscheduled forecasts that are valid for 4 hours unless the SIGMET relates to a hurricane, in which case it is valid for 6 hours.

Reference(s):

FAA AC 00-45H Aviation Weather Services pg. 5-16
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-12

Other Aviation Weather Services

What is a Convective SIGMET?

A Convective SIGMET is issued for thunderstorms.

Instead of SIGMETs, Convective SIGMETs are issued for thunderstorms in the conterminous U.S. (CONUS).  Any Convective SIGMET implies severe or greater turbulence, severe icing, and low-level wind shear.  A Convective SIGMET will be issued when any of the following conditions are occurring or, in the judgment of the forecaster, are expected to occur:

• A line of thunderstorms at least 60 miles long with thunderstorms affecting at least 40 percent of its length
• An area of active thunderstorms affecting at least 3,000 square miles covering at least 40 percent of the area concerned and exhibiting a very strong radar reflectivity intensity or a significant satellite or lightning signature
• Embedded or severe thunderstorm(s) expected to occur for more than 30 minutes during the valid period regardless of the size of the area

A special Convective SIGMET may be issued when any of the following criteria are occurring or, in the judgment of the forecaster, are expected to occur for more than 30 minutes of the valid period.

• Tornado, hail greater than or equal to 3⁄4 inch (at the surface), or wind gusts greater than or equal to 50 knots (at the surface) are reported
• Indications of rapidly changing conditions, if in the forecaster’s judgment, they are not sufficiently described in existing Convective SIGMETs
• Special issuance is not required for a valid Convective SIGMET

Reference(s):

FAA AC 00-45H Aviation Weather Services pg. 5-7
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-12

Other Aviation Weather Services

What is a convective outlook?

A convective outlook primarily indicates the forecast for severe storms or convective activity.

The NWS Storm Prediction Center (SPC) issues narrative and graphical convective outlooks to provide the contiguous U.S. NWS Weather Forecast Offices (WFOs), the public, media and emergency managers with the potential for severe (tornado, wind gusts 50 knots or greater, or hail 1-inch diameter size or greater) and non-severe (general) convection and specific severe weather threats during the following three days.  The Convective Outlook defines areas of slight risk (SLGT), moderate risk (MDT) or high risk (HIGH) of severe thunderstorms for a 24-hour period beginning at 1200 UTC.  The Day 1 and Day 2 Convective Outlooks also depict areas of general thunderstorms (GEN TSTMS), while the Day 1, Day 2, and Day 3 Convective Outlooks may use SEE TEXT for areas where convection may approach or slightly exceed severe criteria.  The outlooks are available on the Storm Prediction Center web site.

Reference(s):

https://www.spc.noaa.gov/products/outlook/
FAA AC 00-45H Aviation Weather Services pg. 5-35

Other Aviation Weather Services

What is a METAR?

A METAR is an observation of current surface weather reported in a standard format.

METARs are issued on a regularly scheduled basis unless significant weather changes have occurred.  A special METAR (SPECI) can be issued at any time between routine METAR reports.  A typical METAR report contains the following information in sequential order: type of report, station identifier, date and time of report, modifier, wind, visibility, weather, sky condition, temperature and dew point, altimeter setting, Zulu time, remarks.

Example: METAR KGGG 161753Z AUTO 14021G26KT 3/4SM +TSRA BR BKN008 OVC012CB 18/17 A2970 RMK PRESFR

Explanation: Routine METAR for Gregg County Airport for the 16th day of the month at 1753Z automated source.  Winds are 140 at 21 knots gusting to 26. Visibility is 3⁄4 statute mile.  Thunderstorms with heavy rain and mist.  Ceiling is broken at 800 feet, overcast at 1,200 feet with cumulonimbus clouds.  Temperature 18 °C and dew point 17 °C.  Barometric pressure is 29.70Hg and the pressure is falling rapidly.

Reference(s):

FAA AC 00-45H Aviation Weather Services pg. 3-1
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-7

Other Aviation Weather Services

What is a Terminal Aerodrome Forecasts (TAF)?

A Terminal Aerodrome Forecasts (TAF) is a weather forecast for the five-statute mile radius around an airport.

Each TAF is valid for a 24 or 30­hour time period and is updated four times a day at 0000Z, 0600Z, 1200Z, and 1800Z.  The TAF utilizes the same descriptors and abbreviations as used in the METAR report.  The TAF includes the following information in sequential order: type of report, station identifier, time and date, valid period dates and times, forecast wind, forecast visibility, forecast significant weather, forecast sky condition, forecast change group and probability.

TAF
KPIR 111130Z 1112/1212
TEMPO 1112/1114 5SM BR
FM1500 16015G25KT P6SM SCT040 BKN250 FM120000 14012KT P6SM BKN080 OVC150 PROB30 1200/1204 3SM TSRA BKN030CB
FM120400 1408KT P6SM SCT040 OVC080
TEMPO 1204/1208 3SM TSRA OVC030CB

Explanation: Routine TAF for Pierre, South Dakota…on the 11th day of the month, at 1130Z…valid for 24 hours from 1200Z on the 11th to 1200Z on the 12th…wind from 150° at 12 knots… visibility greater than 6 SM…broken clouds at 9,000 feet… temporarily, between 1200Z and 1400Z, visibility 5 SM in mist…from 1500Z winds from 160° at 15 knots, gusting to 25 knots visibility greater than 6 SM…clouds scattered at 4,000 feet and broken at 25,000 feet…from 0000Z wind from 140° at 12 knots…visibility greater than 6 SM…clouds broken at 8,000 feet, overcast at 15,000 feet…between 0000Z and 0400Z, there is 30 percent probability of visibility 3 SM…thunderstorm with moderate rain showers…clouds broken at 3,000 feet with cumulonimbus clouds…from 0400Z…winds from 140° at 8 knots…visibility greater than 6 miles…clouds at 4,000 scattered and overcast at 8,000… temporarily between 0400Z and 0800Z…visibility 3 miles… thunderstorms with moderate rain showers…clouds overcast at 3,000 feet with cumulonimbus clouds…end of report (=).

Reference(s):

FAA AC 00-45H Aviation Weather Services pg. 5-75
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-9

Other Aviation Weather Services

What is an Aviation Forecast Discussion?

The Aviation Forecast Discussion is a text interruption from a meteorologist of the local weather conditions.

Aviation Forecast Discussions (AFD) are issued by each weather service forecast office (WFO) to describe the weather conditions within their region as it relates to the creation of the TAF.  These are useful for additional aviation related issues that cannot be encoded into the TAF.  The discussion also gives some reasoning behind the forecast.  These are generated roughly every 6 hours and corresponds to the release of the latest TAFs for that office.  The aviation forecast discussion explains the aviation forecast in greater detail than a traditional TAF.  It highlights possible hazards in the forecast that may not be specifically mentioned in the TAF, possibly due to a low level of confidence that the event will occur.  The frequency of aviation discussion issuances varies between WFOs.

Reference(s):

https://aviationweather.gov/fcstdisc

Other Aviation Weather Services

What is a PIREP?

Pilot weather reports (PIREPS) are weather observations provided by pilots.

PIREPs provide valuable information regarding the conditions as they actually exist in the air, which cannot be gathered from any other source.  Pilots can confirm the height of bases and tops of clouds, locations of wind shear and turbulence, and the location of inflight icing.  PIREPs are filed in a stand format: station identifier, type of report (routine or urgent), time, altitude/flight level, aircraft type, sky cover/cloud layers, weather, air temperature, wind, turbulence, icing and remarks. Below is an example.

KCMH UA /OV APE 230010/TM 1516/FL085/TP BE20/SK BKN065/WX FV03SM HZ FU/TA 20/TB LGT

Explanation:  This a routine PIREP. The pilot is reporting from one zero miles southwest of Appleton VOR;  the time of the report is 1516 UTC;  the altitude is eight thousand five hundred;  the aircraft type is a King Aire 200;  the bases of a broken cloud layer is at six thousand five hundred;  flight visibility 3 miles with haze and smoke;  the air temperature is 20 degrees Celsius and there is light turbulence.

Reference(s):

AIM 2018 7−1−20. Pilot Weather Reports (PIREPs)
FAA AC 00-45H Aviation Weather Services pg. 3-6
FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge pg. 13-8

Other Aviation Weather Services