Definition
An unscheduled weather observation issued from an airport when conditions change significantly between the regular hourly METAR reports. It uses the same format and codes as a METAR but is triggered by specific events such as a shift in wind, a drop in visibility or ceiling, the onset or end of precipitation, thunderstorms, or other operationally important weather changes.
Plain English
An off-schedule weather report from an airport, sent out whenever the weather changes enough to matter, instead of waiting for the next hourly report.
Context Anchor
Pilots encounter this term when checking current airport weather before departure, while en route, or before approach and landing.
Derivation
SPECI comes from the word 'special,' reflecting that this is a special, off-cycle observation issued only when conditions warrant it, rather than on the regular hourly schedule.
Why Pilots Care
Alerts pilots to sudden hazards like reduced visibility or wind changes that affect takeoff, landing, and route decisions.
Intuition Check
Special does not mean more detailed or optional here. It means the report was issued outside the normal schedule because the weather changed enough to require an update.
Example Sentence 1
Before departure, the pilot noticed a SPECI had been issued thirty minutes after the last METAR, showing a sudden drop in visibility due to fog.
Example Sentence 2
Before departure the pilot checked the latest Aviation Selected Special Weather Report for wind shear warnings.