SIGMET

A SIGMET is a weather advisory issued by meteorological authorities to warn pilots and air traffic services of significant and potentially hazardous weather phenomena that could affect the safety of aircraft in flight. Unlike METARs and TAFs, which are routine reports and forecasts, SIGMETs are event-driven and concern dangerous, often fast-developing conditions.

• Warn of severe weather that poses a direct threat to flight safety
• Support ATC rerouting and flow management
• Help pilots avoid hazardous areas in preflight planning or enroute

SIGMETs are issued for specific Flight Information Regions (FIRs) and are time-limited (usually valid for 4 hours).

SIGMETs follow ICAO standardized format and typically include:

• Header and issuing authority
• Time of validity (UTC)
• Affected FIR or airspace
• Weather phenomenon (type, intensity, movement)
• Vertical extent (altitudes affected)
• Geographical area (coordinates or reference points)

Example SIGMET (decoded):

EHAA SIGMET 3 VALID 081000/081400 EHDB–
EHAA AMSTERDAM FIR
SEV TURB OBS AT 1000Z BTN FL100 AND FL200 MOV E 30KT
WKN INTSF.

Translation:

• Amsterdam FIR
• Severe turbulence observed at 10:00 UTC between FL100 and FL200
• moving east at 30 knots
• expected to weaken in intensity

• Preflight briefing tools
• National AIPs and MET services
• ATIS or FIS broadcasts
• VOLMET transmissions
• Integrated into weather overlays on cockpit avionics

• “SIGMET in effect for Vienna FIR: severe icing between FL080 and FL160, embedded thunderstorms, avoid area west of Salzburg”
• “Radar vectors to avoid SIGMET area”
• “Request deviation left of track due to SIGMET turbulence forecast”

• ✅ Review SIGMETs during flight planning
• ✅ Update enroute via VOLMET, ATIS, or FIS
• ✅ Be prepared for re-routing, holding, or delays
• ✅ Use LearnATC to simulate decision-making with SIGMETs in real-time