Sigmet Airmet Gamet

Wing Commander Rajagopal

Significant Met Information

SIGMET, AIRMET and GAMET

  • SIGMET (Significant Meteorological Information) contains weather information significant to the safety of aircraft in flight.
  • In India, SIGMET is issued by the Meteorological Watch Office (MWO) and transmitted to aircraft through the Flight Information Centre (FIC) or Area Control Centre (ACC) at Delhi, Mumbai, Kolkata and Chennai.
  • SIGMET is issued every 3 hours starting from 0100 UTC and is valid for a maximum of 4 hours.
  • For Volcanic Ash and Tropical Cyclones, validity may extend up to 12 hours, with updates issued every 6 hours.
  • SIGMET SST is a SIGMET issued specifically for supersonic flights.
  • AIRMET is a SIGMET intended for low-level flights.
  • GAMET is an area forecast issued for low-level flights and exchanged between neighbouring Flight Information Regions (FIRs).

Conditions for Significant Meteorological Information (SIGMET)

  • SIGMET is issued for the following significant weather phenomena:
    • Thunderstorms:
      • OBSC TS – Obscured Thunderstorm
      • FRQ TS – Frequent Thunderstorms
      • EMBD TS – Embedded Thunderstorms
      • SQL TS – Squall Line Thunderstorms
      • TSGR – Thunderstorms with Hail
    • Tropical Cyclones with sustained winds greater than 34 knots for at least 10 minutes.
    • Severe turbulence caused by strong winds or rotor clouds.
    • Severe icing outside convective clouds or due to freezing rain.
    • Severe mountain waves with updrafts exceeding 3 m/s accompanied by severe turbulence.
    • Heavy dust storms or sandstorms.
    • Volcanic ash.
    • Radioactive cloud.

SIGMET Format

  • ICAO indicator of the FIR, report type and sequence number (e.g., VABB SIGMET 5).
  • Date, time and validity period in UTC (e.g., VALID 271215/271600).
  • Location of the issuing Meteorological Watch Office (MWO).
  • Name of the Flight Information Region (FIR) or Control Area.
  • Weather phenomenon responsible for the SIGMET (e.g., SEV TURB).
  • Whether the phenomenon is Observed (OBS) or Forecast (FCST), together with the observation or forecast time.

SIGMET Position and Movement

  • Location and altitude are reported using geographical features, latitude/longitude, or location indicators followed by flight level (e.g., VAPO FL250).
  • Movement is described using cardinal directions and speed in knots or km/h, followed by intensity trend.
  • Example: MOV SE 40KT WKN (Moving southeast at 40 knots and weakening).
  • Volcanic ash and tropical cyclone SIGMETs include an outlook showing the expected future position beyond the validity period.

SIGMET Decode

  • Originating Meteorological Watch Office (MWO).
  • Message identification.
  • Sequence number.
  • Validity date and time.
  • Intensity and weather phenomenon.
  • Observed or forecast time.
  • Location.
  • Movement or expected movement.
  • Forecast change in intensity.
  • Outlook beyond the validity period.

Example SIGMET

VOMM
SIGMET 5
VALID 101200/101600
SEV TC
OBS AT 1130 UTC
20.2N 89.2E
25 NM NE OF CHENNAI
MOV W 25KT
INTSF
OTLK TC CENTRE
230300 21N 87E
231200 21N 86E

AIRMET Format

  • Date, time and validity period in UTC (e.g., VALID FEB 27/1215Z 27/1600Z).
  • Meteorological situation causing issuance, written in abbreviated plain language together with movement.
  • Example: MET SITUATION AT 1500Z, LOW PRESSURE NEAR MUMBAI COAST.
  • Wind warning for gusts exceeding 20 knots.
  • Forecast wind and temperature.
  • Forecast freezing level.
  • Weather forecast divided into geographical zones.
  • Each zone includes:
    • Visibility.
    • Weather.
    • Cloud base and cloud tops.
  • Aviation warnings such as:
    • Cloud on hills.
    • Icing.
    • Turbulence.
    • Mountain waves.
  • Outlook forecast valid for the following 6 hours.

AIRMET Decode

  • Identifier.
  • Validity date and time.
  • Meteorological situation.
  • Wind warning.
  • Forecast wind and temperature.
  • Freezing level.
  • Forecast zone.
  • Visibility.
  • Weather.
  • Cloud base and cloud top.
  • Weather warning.
  • Outlook forecast.

Example AIRMET

AIRMET
VALID FEB 27/1215Z 27/1600Z
MET SITUATION AT 1500Z, LOW PRESSURE NEAR MUMBAI COAST
STRONG WIND WRG: GUSTS AROUND 40KT
1000FT 330/20KT BECMG 280/40KT PS05
FREEZING LEVEL 3000FT
ZONE 1: SOUTH OF MUMBAI
OCNL 7KM IN RA
6/8 CU/AC
2000FT/14000FT
WRNG MOD ICE AND MOD TURB IN CLD
OUTLOOK UNTIL FEB 19/0100Z