Unscheduled observations that meet special criteria will be reported as a

• A. METAR
• B. AIRMET
• C. SPECI
• D. CWA

Answer: (C)

Unscheduled updates are issued as a SPECI when weather at a station changes in ways that pilots and controllers need to know immediately. METARs are the routine weather observations published on a regular schedule. If between those routine reports the conditions alter significantly—such as a sharp drop in visibility, a lowering or raising ceiling, the development of a thunderstorm, or other notable weather phenomena—the observer issues a SPECI to convey the new conditions promptly. This ensures that flight operations receive timely and accurate information between the normal METAR reports. AIRMETs are broader advisories for more widespread, less severe conditions; CWAs cover en route significant weather, and METARs themselves are the standard routine observations, not the unscheduled update.