A SPECI (Special Meteorological Report) is an unscheduled weather observation issued when airport conditions change significantly enough to warrant an immediate update between routine hourly METAR reports.
How It Works#
Airports issue routine METAR reports on a fixed schedule, typically every hour. When conditions deteriorate or improve sharply, waiting for the next scheduled report could leave pilots operating on outdated information. A SPECI fills that gap.
Specific triggering thresholds determine when a SPECI is issued. The World Meteorological Organization (WMO) and national authorities like the FAA define these criteria. Common triggers include:
- Wind direction shifting by 60 degrees or more with speeds above 10 knots
- Wind speed jumping to, or dropping below, 15 knots
- Visibility crossing certain thresholds (such as 3 SM, 2 SM, or 1 SM)
- Ceiling height crossing thresholds like 3,000, 1,500, 1,000, or 500 feet
- The onset or ending of thunderstorms, freezing precipitation, or other significant phenomena
- Pressure changes exceeding specific limits at some airports
A SPECI uses the exact same format as a standard METAR report. The only difference is the identifier at the start: the word SPECI replaces METAR.
Example in Aviation#
A commercial airport reports clear skies at 0850 local time. By 0910, a fast-moving line of thunderstorms pushes in, dropping visibility below 1 SM with a ceiling of 400 feet overcast. The automated surface observing system (ASOS) triggers a SPECI report immediately.
An inbound flight crew receives the SPECI through their data link system before the next scheduled METAR at 0950. The updated conditions let them reassess their approach minimums and coordinate with dispatch. Without the SPECI, they would have planned the approach using conditions that no longer existed.
Why It Matters#
For instrument pilots flying approaches, weather can change faster than the hourly reporting cycle allows. A SPECI can mean the difference between continuing an approach with accurate data and flying into conditions below minimums on stale information.
Student pilots and weather enthusiasts benefit from understanding SPECIs as well. Recognizing the SPECI identifier on a weather product tells you that conditions shifted sharply at that airport and that the report deserves close attention.
Key Takeaways#
- A SPECI is an unscheduled METAR issued when airport conditions change rapidly.
- It uses the identical format as a METAR, with SPECI replacing METAR as the identifier.
- Triggering criteria include significant shifts in wind, visibility, ceiling, or weather phenomena.
- SPECIs give pilots current data when the next scheduled METAR is too far away.
- Always check for SPECIs when reviewing weather at airports with rapidly changing conditions.