Definition
An unscheduled surface aviation weather report issued between the regular hourly METAR observations whenever a significant change in weather conditions occurs at the reporting station, such as a shift in wind, a drop in visibility, the onset or end of thunderstorms, or a change in ceiling. SPECIs use the same format and codes as a METAR but are triggered by specific criteria rather than the clock.
Plain English
A weather update issued in between the regular hourly reports whenever the weather changes enough to matter. It looks just like a normal METAR but is sent because something noticeable happened.
Context Anchor
Seen when checking current airport weather before a flight, during a flight, or before landing at an airport.
Derivation
Short for 'special.' The name flags that this is a special, off-schedule report rather than the routine hourly observation.
Why Pilots Care
Provides timely notice of deteriorating or improving weather so pilots can adjust plans before flight.
Intuition Check
SPECI does not mean a more detailed weather report. It means an extra report issued because the weather changed enough to matter before the next regular report.
Example Sentence 1
During the briefing the pilot noticed a SPECI showing visibility had dropped to one mile in fog, well below what the earlier METAR had reported.
Example Sentence 2
Before takeoff the pilot checked the latest SPECI for any wind shear alerts.